ARDC Research Link Australia

ORCID Profile
Orcid icon. 0000-0002-8497-2047

Current Organisation
Western Sydney University

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Research Topics

In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.

ANZSRC Field of Research (FoR)

ANZSRC Socio-Economic Objective (SEO)

Publication

Late growing season carbon subsidy in native gymnosperms in a northern temperate forest

Publisher: Oxford University Press (OUP)

Elevated CO2 did not stimulate stem growth in 11 provenances of a globally important hardwood plantation species

Publisher: Frontiers Media SA

Date: 04-06-2020

DOI: 10.3389/FFGC.2020.00066

Publication

Publisher: Wiley

Date: 30-07-2003

DOI: 10.1046/J.1365-2486.2003.00650.X

Publication

Temperature alters the response of hydraulic architecture to CO2 in cotton plants (Gossypium hirsutum)

Publisher: Elsevier BV

Date: 04-2020

DOI: 10.1016/J.ENVEXPBOT.2020.104004

Publication

Endogenous circadian rhythms in pigment composition induce changes in photochemical efficiency in plant canopies

Publisher: Wiley

Date: 30-03-2017

DOI: 10.1111/PCE.12909

Abstract: There is increasing evidence that the circadian clock is a significant driver of photosynthesis that becomes apparent when environmental cues are experimentally held constant. We studied whether the composition of photosynthetic pigments is under circadian regulation, and whether pigment oscillations lead to rhythmic changes in photochemical efficiency. To address these questions, we maintained canopies of bean and cotton, after an entrainment phase, under constant (light or darkness) conditions for 30-48 h. Photosynthesis and quantum yield peaked at subjective noon, and non-photochemical quenching peaked at night. These oscillations were not associated with parallel changes in carbohydrate content or xanthophyll cycle activity. We observed robust oscillations of Chl a/b during constant light in both species, and also under constant darkness in bean, peaking when it would have been night during the entrainment (subjective nights). These oscillations could be attributed to the synthesis and/or degradation of trimeric light-harvesting complex II (reflected by the rhythmic changes in Chl a/b), with the antenna size minimal at night and maximal around subjective noon. Considering together the oscillations of pigments and photochemistry, the observed pattern of changes is counterintuitive if we assume that the plant strategy is to avoid photodamage, but consistent with a strategy where non-stressed plants maximize photosynthesis.

Publication

Responses of the soil microbial community to nitrogen fertilizer regimes and historical exposure to extreme weather events: Flooding or prolonged-drought

Publisher: Elsevier BV

Date: 03-2018

DOI: 10.1016/J.SOILBIO.2017.12.016

Publication

Publisher: Wiley

Date: 07-1996

DOI: 10.1111/J.1469-8137.1996.TB01909.X

Publication

Leaf photosynthetic, economics and hydraulic traits are decoupled among genotypes of a widespread species of eucalypt grown under ambient and elevated CO₂

Publisher: Wiley

Date: 27-04-2016

DOI: 10.1111/1365-2435.12661

Publication

Smart Film Impacts Stomatal Sensitivity of Greenhouse Capsicum Through Altered Light

Publisher: Cold Spring Harbor Laboratory

Date: 24-09-2020

DOI: 10.1101/2020.09.22.309427

Abstract: Optical films that alter light transmittance may reduce energy consumption in high-tech greenhouses, but their impact on crop physiology remains unclear. We compared the stomatal responses of capsicum plants grown hydroponically under control glass (70% diffuse light) or smart glass (SG) film ULR-80, which blocked % of ultraviolet light and 19% of photosynthetically active radiation (PAR). SG had no significant effects on steady-state ( g s ) or maximal ( g max ) stomatal conductance. In contrast, SG reduced stomatal pore size and sensitivity to exogenous ABA thereby increasing rates of leaf water loss, guard cell K + and Cl - efflux, and Ca 2+ influx. The transition between low (100 μmol m −2 s −1 ) and high (1500 μmol m −2 s −1 ) PAR induced faster stomatal closing and opening rates in SG relative to control plants. The fraction of blue light (0% or 10%) did not affect g s , but induced stomatal oscillations in SG plants. Increased expression of stomatal closure and photoreceptor genes in epidermal peels of SG plants is consistent with fast stomatal responses to light changes. In conclusion, light intensity was more critical than spectral quality for optimal stomatal responses of capsicum under SG, and re-engineering of the SG should maximize PAR transmission to maintain a better stomatal development. Capsicum plants grown under SG film exhibit decreased stomatal pore area, higher water loss and reduced ABA-sensitivity. SG-grown plants have faster rates of stomatal closing and opening in response to light intensity changes. SG increases efflux of K + and Cl - and influx of Ca 2+ of guard cells. SG upregulated the expression of key genes involved in stomatal regulation and light sensing.

Publication

Publisher: Wiley

Date: 30-01-2004

DOI: 10.1111/J.1469-8137.2004.00994.X

Publication

Leaf photosynthesis, respiration and stomatal conductance in six Eucalyptus species native to mesic and xeric environments growing in a common garden

Publisher: Oxford University Press (OUP)

Date: 09-2011

DOI: 10.1093/TREEPHYS/TPR087

Abstract: Trees adapted to mesic and xeric habits may differ in a suite of physiological responses that affect leaf-level carbon balance, including the relationship between photosynthesis (A) and respiration at night (R(n)). Understanding the factors that regulate physiological function in mesic and xeric species is critical for predicting changes in growth and distribution under changing climates. In this study, we examined the relationship between A and R(n), and leaf traits that may regulate A and R(n), in six Eucalyptus species native to mesic or xeric ecosystems, during two 24-h cycles in a common garden under high soil moisture. Peak A and R(n) generally were higher in xeric compared with mesic species. Across species, A and R(n) covaried, correlated with leaf mass per area, leaf N per unit area and daytime soluble sugar accumulation. A also covaried with g(s), which accounted for 93% of the variation in A within species. These results suggest that A and R(n) in these six Eucalyptus species were linked through leaf N and carbohydrates. Further, the relationship between A and R(n) across species suggests that differences in this relationship between mesic and xeric Eucalyptus species in their native habitats may be largely driven by environmental factors rather than inter-specific genetic variation.

Publication

Age at flowering differentially affects vegetative and reproductive responses of a determinate annual plant to elevated carbon dioxide

Publisher: Springer Science and Business Media LLC

Date: 08-03-2003

DOI: 10.1007/S00442-003-1186-7

Abstract: Plant population and community dynamics may be altered by increasing atmospheric CO(2) concentrations [[CO(2)]] through intraspecific variation in the responses of vegetative and reproductive growth. Although these responses may be regulated by age at flowering, little is known about the direct effects of age at flowering on growth responses to elevated [CO(2)]. In this study, we examined the interactive effects of elevated [CO(2)] and age at flowering on absolute and relative allocation to vegetative and reproductive growth in the determinate, short-day species Xanthium strumarium L. (common cocklebur). Six cohorts were planted at 5-day intervals in chambers maintained at either 365 or 730 micro mol mol(-1) CO(2), with an 18-h photoperiod and a non-limiting nutrient supply. All plants were simultaneously induced to flower by switching the photoperiod to 12 h for 2 days, then switching back to an 18-h photoperiod for the remainder of the experiment. All plants were harvested 15 days after the onset of flowering. Total plant biomass increased 11-41% with increasing [CO(2)] and 45% from the youngest to the oldest cohort. Vegetative growth responses to elevated [CO(2)] significantly increased with increasing age at flowering, associated with increasing sink relative to source capacity. In contrast, total fruit mass decreased 32% from the youngest to the oldest cohort and was not significantly affected by CO(2) supply. Relative biomass allocation to fruit decreased 47% from the youngest to the oldest cohort, reflecting decreased numbers of fruit, and 6-28% with increasing [CO(2)], reflecting decreased mean mass per mature fruit. Our findings suggest that elevated [CO(2)] may increase vegetative growth in Xanthium without increasing reproductive biomass, and that age at flowering may influence these responses through effects on source:sink balance. Further, changes in the allometric relationship between vegetative and reproductive growth associated with growth in elevated [CO(2)] suggest that long-term population and community-level responses to elevated [CO(2)] may differ substantially from predictions based on vegetative responses.

Publication

Coordination of hydraulic and morphological traits across dominant grasses in eastern Australia

Publisher: Wiley

Date: 10-02-2023

DOI: 10.1111/1365-2435.14283

Abstract: Leaf hydraulic traits characterize plant drought tolerance and responses to climate change. Yet, plant hydraulics are biased towards northern hemisphere woody species. We collected rhizomes of several perennial grass species along a precipitation gradient in eastern Australia and grew them in an experimental pot study to investigate potential trade‐offs between drought tolerance and plant morphology. We measured the following leaf hydraulic traits: the leaf water potential (Ψ leaf ) at 50% and 88% loss of leaf hydraulic conductance (P50 Kleaf and P88 Kleaf ), the Ψ leaf at 50% loss of stomatal conductance (P50 gs ), leaf turgor loss point (TLP), leaf dry matter content (LDMC), leaf modulus of elasticity (ε), and the slope of the relationship between predawn and midday Ψ leaf . We also measured basal area, tiller density, seed head density, root collar diameter, plant height, and aboveground biomass of each in idual. As expected, grass species varied widely in leaf‐level drought tolerance, with loss of 88% hydraulic conductance occurring at a Ψ leaf ranging from −1.52 to −4.01 MPa. However, all but one species lost leaf turgor, and most reached P50 gs before this critical threshold. Taller more productive grass species tended to have drought vulnerable leaves characterized by low LDMC and less negative P88 Kleaf . Species with greater tiller production experienced stomatal closure and lost turgor at more negative Ψ leaf . Although our s le size was limited, we found no relationships between these species' traits and their climate of origin. Overall, we identified important hydraulic and morphological trade‐offs in Australian grasses that were surprisingly similar to those observed for woody plants: (1) xylem of taller species was less drought tolerant and (2) turgor loss occurs and stomatal closure begins before significant loss of K leaf . These data build upon a small yet growing field of grass hydraulics and may be informative of species responses to further drought intensification in Australia. Read the free Plain Language Summary for this article on the Journal blog.

Publication

To what extent can rising [CO2] ameliorate plant drought stress?

Publisher: Wiley

Date: 28-07-2021

DOI: 10.1111/NPH.17540

Abstract: Plant responses to elevated atmospheric carbon dioxide (eCO 2 ) have been hypothesized as a key mechanism that may ameliorate the impact of future drought. Yet, despite decades of experiments, the question of whether eCO 2 reduces plant water use, yielding ‘water savings’ that can be used to maintain plant function during periods of water stress, remains unresolved. In this Viewpoint, we identify the experimental challenges and limitations to our understanding of plant responses to drought under eCO 2 . In particular, we argue that future studies need to move beyond exploring whether eCO 2 played ‘a role’ or ‘no role’ in responses to drought, but instead more carefully consider the timescales and conditions that would induce an influence. We also argue that considering emergent differences in soil water content may be an insufficient means of assessing the impact of eCO 2 . We identify eCO 2 impact during severe drought (e.g. to the point of mortality), interactions with future changes in vapour pressure deficit and uncertainty about changes in leaf area as key gaps in our current understanding. New insights into CO 2 × drought interactions are essential to better constrain model theory that governs future climate model projections of land–atmosphere interactions during periods of water stress.

Publication

Continuous light may induce photosynthetic downregulation in onion – consequences for growth and biomass partitioning

Publisher: Wiley

Date: 07-09-2005

DOI: 10.1111/J.1399-3054.2005.00560.X

Publication

Leaf trait variation is similar among genotypes of Eucalyptus camaldulensis from differing climates and arises in plastic responses to the seasons rather than water avai

Publisher: Wiley

Date: 06-05-2020

DOI: 10.1111/NPH.16579

Publication

Plant growth in elevated CO ₂ alters mitochondrial number and chloroplast fine structure

Publisher: Proceedings of the National Academy of Sciences

Date: 27-02-2001

DOI: 10.1073/PNAS.041620898

Abstract: With increasing interest in the effects of elevated atmospheric CO 2 on plant growth and the global carbon balance, there is a need for greater understanding of how plants respond to variations in atmospheric partial pressure of CO 2 . Our research shows that elevated CO 2 produces significant fine structural changes in major cellular organelles that appear to be an important component of the metabolic responses of plants to this global change. Nine species (representing seven plant families) in several experimental facilities with different CO 2 -dosing technologies were examined. Growth in elevated CO 2 increased numbers of mitochondria per unit cell area by 1.3–2.4 times the number in control plants grown in lower CO 2 and produced a statistically significant increase in the amount of chloroplast stroma (nonappressed) thylakoid membranes compared with those in lower CO 2 treatments. There was no observable change in size of the mitochondria. However, in contrast to the CO 2 effect on mitochondrial number, elevated CO 2 promoted a decrease in the rate of mass-based dark respiration. These changes may reflect a major shift in plant metabolism and energy balance that may help to explain enhanced plant productivity in response to elevated atmospheric CO 2 concentrations.

Publication

Effects of carbon dioxide and nitrogen on growth and nitrogen uptake in ponderosa and loblolly pine

Publisher: Wiley

Date: 03-1998

DOI: 10.2134/JEQ1998.00472425002700020024X

Publication

Publisher: Wiley

Date: 04-1998

DOI: 10.1046/J.1365-3040.1998.00285.X

Publication

Publisher: Wiley

Date: 2009

DOI: 10.1111/J.1365-2486.2008.01710.X

Publication

Assessing community and ecosystem sensitivity to climate change – toward a more comparative approach

Publisher: Wiley

Date: 03-2017

DOI: 10.1111/JVS.12524

Publication

Precipitation timing and magnitude differentially affect aboveground annual net primary productivity in three perennial species in a Chihuahuan Desert grassland

Publisher: Wiley

Date: 03-12-2009

DOI: 10.1111/J.1469-8137.2008.02643.X

Abstract: DOI: 10.1111/j.1469-8137.2008.02695.x Commentary p 5

Publication

Convergence across biomes to a common rain-use efficiency

Publisher: Springer Science and Business Media LLC

Date: 06-2004

DOI: 10.1038/NATURE02561

Publication

Publisher: Elsevier BV

Date: 07-2019

DOI: 10.1016/J.AGRFORMET.2019.03.024

Publication

Panicum milioides (C 3-C 4) does not have improved water or nitrogen economies relative to C 3 and C 4 congeners exposed to industrial-age climate change

Publisher: Oxford University Press (OUP)

Date: 09-02-2011

DOI: 10.1093/JXB/ERR005

Abstract: The physiological implications of C(3)-C(4) photosynthesis were investigated using closely related Panicum species exposed to industrial-age climate change. Panicum bisulcatum (C(3)), P. milioides (C(3)-C(4)), and P. coloratum (C(4)) were grown in a glasshouse at three CO(2) concentrations ([CO(2)]: 280, 400, and 650 μl l(-1)) and two air temperatures [ambient (27/19 °C day/night) and ambient + 4 °C] for 12 weeks. Under current ambient [CO(2)] and temperature, the C(3)-C(4) species had higher photosynthetic rates and lower stomatal limitation and electron cost of photosynthesis relative to the C(3) species. These photosynthetic advantages did not improve leaf- or plant-level water (WUE) or nitrogen (NUE) use efficiencies of the C(3)-C(4) relative to the C(3) Panicum species. In contrast, the C(4) species had higher photosynthetic rates and WUE but similar NUE to the C(3) species. Increasing [CO(2)] mainly stimulated photosynthesis of the C(3) and C(3)-C(4) species, while high temperature had no or negative effects on photosynthesis of the Panicum species. Under ambient temperature, increasing [CO(2)] enhanced the biomass of the C(3) species only. Under high temperature, increasing [CO(2)] enhanced the biomass of the C(3) and C(3)-C(4) species to the same extent, indicating increased CO(2) limitation in the C(3)-C(4) intermediate at high temperature. Growth [CO(2)] and temperature had complex interactive effects, but did not alter the ranking of key physiological parameters amongst the Panicum species. In conclusion, the ability of C(3)-C(4) intermediate species partially to recycle photorespired CO(2) did not improve WUE or NUE relative to congeneric C(3) or C(4) species grown under varying [CO(2)] and temperature conditions.

Publication

Smart glass impacts stomatal sensitivity of greenhouse Capsicum through altered light

Publisher: Oxford University Press (OUP)

Date: 23-01-2021

DOI: 10.1093/JXB/ERAB028

Abstract: Optical films that alter light transmittance may reduce energy consumption in high-tech greenhouses, but their impact on crop physiology remains unclear. We compared the stomatal responses of Capsicum plants grown hydroponically under control glass (70% diffuse light) or the smart glass (SG) film ULR-80, which blocked & % of short-wave radiation and ~9% of photosynthetically active radiation (PAR). SG had no significant effects on steady-state (gs) or maximal (gmax) stomatal conductance. In contrast, SG reduced stomatal pore size and sensitivity to exogenous abscisic acid (ABA), thereby increasing rates of leaf water loss, guard cell K+ and Cl– efflux, and Ca2+ influx. SG induced faster stomatal closing and opening rates on transition between low (100 µmol m–2 s–1) and high PAR (1500 µmol m–2 s–1), which compromised water use efficiency relative to control plants. The fraction of blue light (0% or 10%) did not affect gs in either treatment. Increased expression of stomatal closure and photoreceptor genes in epidermal peels of SG plants is consistent with fast stomatal responses to light changes. In conclusion, stomatal responses of Capsicum to SG were more affected by changes in light intensity than spectral quality, and re-engineering of the SG should maximize PAR transmission, and hence CO2 assimilation.

Publication

Phosphorus supply drives nonlinear responses of cottonwood (Populus deltoides) to increases in CO2 concentration from glacial to future concentrations

Publisher: Wiley

Publisher: Springer Science and Business Media LLC

Date: 10-1994

DOI: 10.1038/371500A0

Publication

Increasing aridity will not offset CO2 fertilization in fast‐growing eucalypts with access to deep soil water

Publisher: Wiley

Date: 25-03-2021

DOI: 10.1111/GCB.15590

Publication

Utilizing intraspecific variation in phenotypic plasticity to bolster agricultural and forest productivity under climate change

Publisher: Wiley

Date: 09-2014

DOI: 10.1111/PCE.12424

Abstract: Climate change threatens the ability of agriculture and forestry to meet growing global demands for food, fibre and wood products. Information gathered from genotype-by-environment interactions (G × E), which demonstrate intraspecific variation in phenotypic plasticity (the ability of a genotype to alter its phenotype in response to environmental change), may prove important for bolstering agricultural and forest productivity under climate change. Nonetheless, very few studies have explicitly quantified genotype plasticity-productivity relationships in agriculture or forestry. Here, we conceptualize the importance of intraspecific variation in agricultural and forest species plasticity, and discuss the physiological and genetic factors contributing to intraspecific variation in phenotypic plasticity. Our discussion highlights the need for an integrated understanding of the mechanisms of G × E, more extensive assessments of genotypic responses to climate change under field conditions, and explicit testing of genotype plasticity-productivity relationships. Ultimately, further investigation of intraspecific variation in phenotypic plasticity in agriculture and forestry may prove important for identifying genotypes capable of increasing or sustaining productivity under more extreme climatic conditions.

Publication

Publisher: Oxford University Press (OUP)

Date: 11-1990

DOI: 10.1093/OXFORDJOURNALS.AOB.A088064

Publication

Quantifying ecological memory in plant and ecosystem processes

Publisher: Wiley

Date: 19-12-2014

DOI: 10.1111/ELE.12399

Abstract: The role of time in ecology has a long history of investigation, but ecologists have largely restricted their attention to the influence of concurrent abiotic conditions on rates and magnitudes of important ecological processes. Recently, however, ecologists have improved their understanding of ecological processes by explicitly considering the effects of antecedent conditions. To broadly help in studying the role of time, we evaluate the length, temporal pattern, and strength of memory with respect to the influence of antecedent conditions on current ecological dynamics. We developed the stochastic antecedent modelling (SAM) framework as a flexible analytic approach for evaluating exogenous and endogenous process components of memory in a system of interest. We designed SAM to be useful in revealing novel insights promoting further study, illustrated in four ex les with different degrees of complexity and varying time scales: stomatal conductance, soil respiration, ecosystem productivity, and tree growth. Models with antecedent effects explained an additional 18-28% of response variation compared to models without antecedent effects. Moreover, SAM also enabled identification of potential mechanisms that underlie components of memory, thus revealing temporal properties that are not apparent from traditional treatments of ecological time-series data and facilitating new hypothesis generation and additional research.

Publication

Aridity drives clinal patterns in leaf traits and responsiveness to precipitation in a broadly distributed Australian tree species

Publisher: Wiley

Date: 17-03-2023

DOI: 10.1002/PEI3.10102

Abstract: Aridity shapes species distributions and plant growth and function worldwide. Yet, plant traits often show complex relationships with aridity, challenging our understanding of aridity as a driver of evolutionary adaptation. We grew nine genotypes of Eucalyptus camaldulensis subsp. camaldulensis sourced from an aridity gradient together in the field for ~650 days under low and high precipitation treatments. Eucalyptus camaldulesis is considered a phreatophyte (deep‐rooted species that utilizes groundwater), so we hypothesized that genotypes from more arid environments would show lower aboveground productivity, higher leaf gas‐exchange rates, and greater tolerance/avoidance of dry surface soils (indicated by lower responsiveness) than genotypes from less arid environments. Aridity predicted genotype responses to precipitation, with more arid genotypes showing lower responsiveness to reduced precipitation and dry surface conditions than less arid genotypes. Under low precipitation, genotype net photosynthesis and stomatal conductance increased with home‐climate aridity. Across treatments, genotype intrinsic water‐use efficiency and osmotic potential declined with increasing aridity while photosynthetic capacity (Rubisco carboxylation and RuBP regeneration) increased with aridity. The observed clinal patterns indicate that E. camaldulensis genotypes from extremely arid environments possess a unique strategy defined by lower responsiveness to dry surface soils, low water‐use efficiency, and high photosynthetic capacity. This strategy could be underpinned by deep rooting and could be adaptive under arid conditions where heat avoidance is critical and water demand is high.

Publication

Desiccation time during drought is highly predictable across species of Eucalyptus from contrasting climates

Publisher: Wiley

Date: 08-08-2019

DOI: 10.1111/NPH.16042

Abstract: Catastrophic failure of the water transport pathway in trees is a principal mechanism of mortality during extreme drought. To be able to predict the probability of mortality at an in idual and landscape scale we need knowledge of the time for plants to reach critical levels of hydraulic failure. We grew plants of eight species of Eucalyptus originating from contrasting climates before allowing a subset to dehydrate. We tested whether a trait-based model of time to plant desiccation t

Publication

Inter- and intra-specific variation in nocturnal water transport in Eucalyptus

Publisher: Oxford University Press (OUP)

Date: 23-03-2010

DOI: 10.1093/TREEPHYS/TPQ009

Abstract: To identify environmental and biological drivers of nocturnal vapour exchange, we quantified intra-annual, intra- and inter-specific variation in nocturnal water transport among ecologically erse Eucalyptus species. We measured sap flux (J(s)) and leaf physiology (leaf surface conductance (g(s)), transpiration (E) and water potential (Psi(l))) in three to five trees of eight species. Over 1 year, nocturnal J(s) (J(s,n)) contributed 5-7% of total J(s) in the eight species. The principal environmental driver of J(s,n) was the product of atmospheric vapour pressure deficit (D) and wind speed (U). Selected observations suggest that trees with higher proportions of young foliage may exhibit greater J(s,n) and nocturnal g(s) (g(s,n)). Compared with other tree taxa, nocturnal water use in Eucalyptus was relatively low and more variable within than between species, suggesting that (i) Eucalyptus as a group exerts strong nocturnal stomatal control over water loss and (ii) prediction of nocturnal flux in Eucalyptus may depend on simultaneous knowledge of intra-specific tree traits and nocturnal atmospheric conditions.

Publication

Embolism recovery strategies and nocturnal water loss across species influenced by biogeographic origin

Publisher: Wiley

Date: 13-04-2019

DOI: 10.1002/ECE3.5126

Publication

Nitrogenase activity and N 2 fixation are stimulated by elevated CO 2 in a tropical N 2 -fixing tree

Publisher: Springer Science and Business Media LLC

Date: 07-01-1997

DOI: 10.1007/S004420050054

Abstract: Seeds of Gliricidia sepium, a fast-growing woody legume native to seasonal tropical forests of Central America, were inoculated with N

Publication

Long‐term effects of elevated CO2 and nutrients on photosynthesis and rubisco in loblolly pine seedlings

Publisher: Wiley

Date: 09-1993

DOI: 10.1111/J.1365-3040.1993.TB00508.X

Publication

The peaked response of transpiration rate to vapour pressure deficit in field conditions can be explained by the temperature optimum of photosynthesis

Publisher: Elsevier BV

Date: 06-2014

DOI: 10.1016/J.AGRFORMET.2013.12.007

Publication

Towards Youth Mental Health System Reform: An Evaluation of Participatory Systems Modelling in the Australian Capital Territory

Publisher: MDPI AG

Date: 28-07-2023

DOI: 10.3390/SYSTEMS11080386

Abstract: Australia’s mental health system is failing young people. Calls for accountability, strategic long-term policy planning, and regional leadership have been identified as solutions to guide mental health reform. Developing system dynamics models using a participatory approach (participatory systems modelling (PSM)) is recognized as a useful method that can support decision-making for strategic reform. This paper reports evaluation findings of a youth mental health PSM process conducted in the Australian Capital Territory (ACT). Baseline and follow-up mixed-methods evaluation data were collected in 2022 across erse stakeholder groups to investigate the feasibility, value, impact, and sustainability of PSM. Although youth mental health system reform was viewed as desirable and a necessity across all stakeholder groups, shared perceptions of disabling powerless was observed regarding their ability to influence current decision-making processes to improve the youth mental health system. This suggests greater accountability is required to support systemic reform in youth mental health. PSM offers promise in improving transparency and accountability of decision-making for youth mental health, as exemplified in the ACT. However, more support and time are required to facilitate transformational change. Future research should investigate empowerment strategies to complement the implementation of findings from dynamic models developed through PSM, as well as the effectiveness of regional youth mental health policy decision-making supported by systems modelling.

Publication

Physiological acclimation of a grass species occurs during sustained but not repeated drought events

Publisher: Elsevier BV

Date: 03-2020

DOI: 10.1016/J.ENVEXPBOT.2019.103954

Publication

Impacts of drought on leaf respiration in darkness and light in Eucalyptus saligna exposed to industrial-age atmospheric CO2 and growth temperature

Publisher: Wiley

Date: 22-03-2011

DOI: 10.1111/J.1469-8137.2011.03673.X

Abstract: Our study assessed the impact of a wide range of industrial-age climate scenarios on leaf respiration (R) in Eucalyptus saligna. Well-watered or sustained drought-treated plants were grown in glasshouses differing in atmospheric CO₂ concentration ([CO₂]) (280, 400 and 640 μl l⁻¹) and temperature (26 and 30°C). Rates of R in darkness (R(dark) ) and light (R(light) ), photosynthesis (A) and related leaf traits (mass : area relationships, and nitrogen, phosphorus, starch and sugar concentrations) were measured. Light inhibited R in all cases (R(light) < R(dark) ) (well-watered: 40% drought-treated: 73%). Growth [CO₂] and temperature had little impact on area-based rates of R(dark) or R(light) , with R(light) exhibiting minimal thermal acclimation. By contrast, sustained drought resulted in reduced R(dark), R(light) and A, with the inhibitory effect of drought on A and R(light) (c. 50-70%) greater than that on R(dark) (c. 15%). Drought effects were fully reversible after watering. Variability in R(light) appeared to be dependent on the underlying rate of R(dark) and associated Rubisco activity. Collectively, our data suggest that there is an asynchronous response of leaf carbon metabolism to drought, and a tighter coupling between R(light) and A than between R(dark) and A, under both past and future climate scenarios. These findings have important implications for ecosystem/global models seeking to predict carbon cycling.

Publication

Seasonal response of photosynthetic electron transport and energy dissipation in the eighth year of exposure to elevated atmospheric CO 2 (FACE) in Pinus taeda (loblolly pine)

Publisher: Oxford University Press (OUP)

Date: 27-03-2009

DOI: 10.1093/TREEPHYS/TPP019

Abstract: To determine the effect of growth under elevated CO(2) partial pressures (pCO(2)) on photosynthetic electron transport and photoprotective energy dissipation, we examined light-saturated net photosynthetic CO(2) assimilation (A(sat)), the capacity for photosynthetic O(2) evolution, chlorophyll fluorescence emission and the pigment composition of upper-canopy loblolly pine needles in the eighth year of exposure to elevated pCO(2) (20 Pa above ambient) at the free-air CO(2) enrichment facility in the Duke Forest. During the summer growing season, A(sat) was 50% higher in current-year needles and 24% higher in year-old needles in elevated pCO(2) in comparison with needles of the same age cohort in ambient pCO(2). Thus, photosynthetic down-regulation at elevated pCO(2) was observed in the summer in year-old needles. In the winter, A(sat) was not significantly affected by growth pCO(2). Reductions in A(sat), the capacity for photosynthetic O(2) evolution and photosystem II (PSII) efficiency in the light-acclimated and fully-oxidized states were observed in the winter when compared to summer. Growth at elevated pCO(2) had no significant effect on the capacity for photosynthetic O(2) evolution, PSII efficiencies in the light-acclimated and fully-oxidized states, chlorophyll content or the size and conversion state of the xanthophyll cycle, regardless of season or needle age cohort. Therefore, we observed no evidence that photosynthetic electron transport or photoprotective energy dissipation responded to compensate for the effects of elevated pCO(2) on Calvin cycle activity.

Publication

Photosynthetic responses of two eucalypts to industrial-age changes in atmospheric [CO2] and temperature

Publisher: Wiley

Date: 07-09-2010

DOI: 10.1111/J.1365-3040.2010.02172.X

Abstract: The unabated rise in atmospheric [CO(2)] is associated with increased air temperature. Yet, few CO(2)-enrichment studies have considered pre-industrial [CO(2)] or warming. Consequently, we quantified the interactive effects of growth [CO(2)] and temperature on photosynthesis of faster-growing Eucalyptus saligna and slower-growing E. sideroxylon. Well-watered and -fertilized tree seedlings were grown in a glasshouse at three atmospheric [CO(2)] (290, 400, and 650 µL L(-1)), and ambient (26/18 °C, day/night) and high (ambient + 4 °C) air temperature. Despite differences in growth rate, both eucalypts responded similarly to [CO(2)] and temperature treatments with few interactive effects. Light-saturated photosynthesis (A(sat)) and light- and [CO(2)]-saturated photosynthesis (A(max) ) increased by ∼ 50% and ∼ 10%, respectively, with each step-increase in growth [CO(2)], underpinned by a corresponding 6-11% up-regulation of maximal electron transport rate (J(max)). Maximal carboxylation rate (V(cmax)) was not affected by growth [CO(2)]. Thermal photosynthetic acclimation occurred such that A(sat) and A(max) were similar in ambient- and high-temperature-grown plants. At high temperature, the thermal optimum of A(sat) increased by 2-7 °C across [CO(2)] treatments. These results are the first to suggest that photosynthesis of well-watered and -fertilized eucalypt seedlings will remain strongly responsive to increasing atmospheric [CO(2)] in a future, warmer climate.

Publication

Sensitivity of plants to changing atmospheric CO₂ concentration: from the geological past to the next century

Publisher: Frontiers Media SA

Date: 11-10-2019

DOI: 10.3389/FGENE.2019.00956

Publication

Interactive effects of elevated CO 2 and drought on nocturnal water fluxes in Eucalyptus saligna

Publisher: Oxford University Press (OUP)

Date: 25-05-2011

DOI: 10.1093/TREEPHYS/TPR024

Abstract: Nocturnal water flux has been observed in trees under a variety of environmental conditions and can be a significant contributor to diel canopy water flux. Elevated atmospheric CO(2) (elevated [CO(2)]) can have an important effect on day-time plant water fluxes, but it is not known whether it also affects nocturnal water fluxes. We examined the effects of elevated [CO(2)] on nocturnal water flux of field-grown Eucalyptus saligna trees using sap flux through the tree stem expressed on a sapwood area (J(s)) and leaf area (E(t)) basis. After 19 months growth under well-watered conditions, drought was imposed by withholding water for 5 months in the summer, ending with a rain event that restored soil moisture. Reductions in J(s) and E(t) were observed during the severe drought period in the dry treatment under elevated [CO(2)], but not during moderate- and post-drought periods. Elevated [CO(2)] affected night-time sap flux density which included the stem recharge period, called 'total night flux' (19:00 to 05:00, J(s,r)), but not during the post-recharge period, which primarily consisted of canopy transpiration (23:00 to 05:00, J(s,c)). Elevated [CO(2)] wet (EW) trees exhibited higher J(s,r) than ambient [CO(2)] wet trees (AW) indicating greater water flux in elevated [CO(2)] under well-watered conditions. However, under drought conditions, elevated [CO(2)] dry (ED) trees exhibited significantly lower J(s,r) than ambient [CO(2)] dry trees (AD), indicating less water flux during stem recharge under elevated [CO(2)]. J(s,c) did not differ between ambient and elevated [CO(2)]. Vapour pressure deficit (D) was clearly the major influence on night-time sap flux. D was positively correlated with J(s,r) and had its greatest impact on J(s,r) at high D in ambient [CO(2)]. Our results suggest that elevated [CO(2)] may reduce night-time water flux in E. saligna when soil water content is low and D is high. While elevated [CO(2)] affected J(s,r), it did not affect day-time water flux in wet soil, suggesting that the responses of J(s,r) to environmental factors cannot be directly inferred from day-time patterns. Changes in J(s,r) are likely to influence pre-dawn leaf water potential, and plant responses to water stress. Nocturnal fluxes are clearly important for predicting effects of climate change on forest physiology and hydrology.

Publication

Effects of leaf age and tree size on stomatal and mesophyll limitations to photosynthesis in mountain beech (Nothofagus solandrii var. cliffortiodes)

Publisher: Oxford University Press (OUP)

Date: 22-04-2011

DOI: 10.1093/TREEPHYS/TPR021

Abstract: Mesophyll conductance, g(m), was estimated from measurements of stomatal conductance to carbon dioxide transfer, g(s), photosynthesis, A, and chlorophyll fluorescence for Year 0 (current-year) and Year 1 (1-year-old) fully sunlit leaves from short (2 m tall, 10-year-old) and tall (15 m tall, 120-year-old) Nothofagus solandrii var. cliffortiodes trees growing in adjacent stands. Rates of photosynthesis at saturating irradiance and ambient CO(2) partial pressure, A(satQ), were 25% lower and maximum rates of carboxylation, V(cmax), were 44% lower in Year 1 leaves compared with Year 0 leaves across both tree sizes. Although g(s) and g(m) were not significantly different between Year 0 and Year 1 leaves and g(s) was not significantly different between tree heights, g(m) was significantly (19%) lower for leaves on tall trees compared with leaves on short trees. Overall, V(cmax) was 60% higher when expressed on the basis of CO(2) partial pressure at the chloroplasts, C(c), compared with V(cmax) on the basis of intercellular CO(2) partial pressure, C(i), but this varied with leaf age and tree size. To interpret the relative stomatal and mesophyll limitations to photosynthesis, we used a model of carbon isotopic composition for whole leaves incorporating g(m) effects to generate a surface of 'operating values' of A over the growing season for all leaf classes. Our analysis showed that A was slightly higher for leaves on short compared with tall trees, but lower g(m) apparently reduced actual A substantially compared with A(satQ). Our findings showed that lower rates of photosynthesis in Year 1 leaves compared with Year 0 leaves were attributable more to increased biochemical limitation to photosynthesis in Year 1 leaves than differences in g(m). However, lower A in leaves on tall trees compared with those on short trees could be attributed in part to lower g(m) and higher stomatal, L(s), and mesophyll, L(m), limitations to photosynthesis, consistent with steeper hydraulic gradients in tall trees.

Publication

Rates of nocturnal transpiration in two evergreen temperate woodland species with differing water-use strategies

Publisher: Oxford University Press (OUP)

Date: 21-06-2010

DOI: 10.1093/TREEPHYS/TPQ053

Abstract: Nocturnal fluxes may be a significant factor in the annual water budget of forested ecosystems. Here, we assessed sap flow in two co-occurring evergreen species (Eucalyptus parramattensis and Angophora bakeri) in a temperate woodland for 2 years in order to quantify the magnitude of seasonal nocturnal sap flow (E(n)) under different environmental conditions. The two species showed different diurnal water relations, demonstrated by different diurnal curves of stomatal conductance, sap flow and leaf water potential. The relative influence of several microclimatic variables, including wind speed (U), vapour pressure deficit (D), the product of U and D (UD) and soil moisture content, were quantified. D exerted the strongest influence on E(n) (r² = 0.59-0.86), soil moisture content influenced E(n) when D was constant, but U and UD did not generally influence E(n). In both species, cuticular conductance (G(c)) was a small proportion of total leaf conductance (G(s)) and was not a major pathway for E(n). We found that E(n) was primarily a function of transpiration from the canopy rather than refilling of stem storage, with canopy transpiration accounting for 50-70% of nocturnal flows. Mean E(n) was 6-8% of the 24-h flux across seasons (spring, summer and winter), but was up to 19% of the 24-h flux on some days in both species. Despite different daytime strategies in water use of the two species, both species demonstrated low night-time water loss, suggesting similar controls on water loss at night. In order to account for the impact of E(n) on pre-dawn leaf water potential arising from the influence of disequilibria between root zone and leaf water potential, we also developed a simple model to more accurately predict soil water potential (ψ(s)).

Publication

Genetic adaptation and phenotypic plasticity contribute to greater leaf hydraulic tolerance in response to drought in warmer climates

Publisher: Oxford University Press (OUP)

Date: 09-02-2017

DOI: 10.1093/TREEPHYS/TPX005

Abstract: The ability of plants to maintain an intact water transport system in leaves under drought conditions is intimately linked to survival and can been be seen as adaptive in shaping species climatic limits. Large differences in leaf hydraulic vulnerability to drought are known among species from contrasting climates, yet whether this trait varies among populations within a single species and, furthermore, whether it is altered by changes in growth conditions, remain unclear. We examined intraspecific variation in both leaf water transport capacity (Kleaf) and leaf hydraulic vulnerability to drought (P50leaf) among eight populations of Corymbia calophylla (R. Br.) K.D. Hill & L.A.S. Johnson (Myrtaceae) from both cool and warm climatic regions grown reciprocally under two temperature treatments representing the cool and warm edge of the species distribution. Kleaf did not vary between cool and warm-climate populations, nor was it affected by variable growth temperature. In contrast, population origin and growth temperature independently altered P50leaf. Using data pooled across growth temperatures, cool-climate populations showed significantly higher leaf hydraulic vulnerability (P50leaf = -3.55 ± 0.18 MPa) than warm-climate populations (P50leaf = -3.78 ± 0.08 MPa). Across populations, P50leaf decreased as population home-climate temperature increased, but was unrelated to rainfall and aridity. For populations from both cool and warm climatic regions, P50leaf was lower under the warmer growth conditions. These results provide evidence of trait plasticity in leaf hydraulic vulnerability to drought in response to variable growth temperature. Furthermore, they suggest that climate, and in particular temperature, may be a strong selective force in shaping intraspecific variation in leaf hydraulic vulnerability to drought.

Publication

Effects of elevated atmospheric [CO2] on instantaneous transpiration efficiency at leaf and canopy scales in Eucalyptus saligna

Publisher: Wiley

Date: 19-09-2012

DOI: 10.1111/J.1365-2486.2011.02526.X

Publication

Seasonal response of photosynthesis to elevated CO2 in loblolly pine (Pinus taeda L.) over two growing seasons

Publisher: Wiley

Date: 04-1996

DOI: 10.1111/J.1365-2486.1996.TB00055.X

Publication

Acclimation and adaptation components of the temperature dependence of plant photosynthesis at the global scale

Publisher: Wiley

Date: 08-02-2019

DOI: 10.1111/NPH.15668

Abstract: The temperature response of photosynthesis is one of the key factors determining predicted responses to warming in global vegetation models (GVMs). The response may vary geographically, owing to genetic adaptation to climate, and temporally, as a result of acclimation to changes in ambient temperature. Our goal was to develop a robust quantitative global model representing acclimation and adaptation of photosynthetic temperature responses. We quantified and modelled key mechanisms responsible for photosynthetic temperature acclimation and adaptation using a global dataset of photosynthetic CO

Publication

Allometric Estimates of Aboveground Biomass Using Cover and Height Are Improved by Increasing Specificity of Plant Functional Groups in Eastern Australian Rangelands

Publisher: Elsevier BV

Date: 05-2020

DOI: 10.1016/J.RAMA.2020.01.009

Publication

An empirical method that separates irreversible stem radial growth from bark water content changes in trees: theory and case studies

Publisher: Wiley

Date: 06-01-2017

DOI: 10.1111/PCE.12863

Publication

More than iso/anisohydry: Hydroscapes integrate plant water use and drought tolerance traits in 10 eucalypt species from contrasting climates

Publisher: Wiley

Date: 07-04-2019

DOI: 10.1111/1365-2435.13320

Publication

Effects of elevated atmospheric CO₂ concentration on leaf dark respiration of Xanthium strumarium in light and in darkness

Publisher: Proceedings of the National Academy of Sciences

Date: 27-02-2001

DOI: 10.1073/PNAS.051622998

Abstract: Leaf dark respiration ( R ) is an important component of plant carbon balance, but the effects of rising atmospheric CO 2 on leaf R during illumination are largely unknown. We studied the effects of elevated CO 2 on leaf R in light ( R L ) and in darkness ( R D ) in Xanthium strumarium at different developmental stages. Leaf R L was estimated by using the Kok method, whereas leaf R D was measured as the rate of CO 2 efflux at zero light. Leaf R L and R D were significantly higher at elevated than at ambient CO 2 throughout the growing period. Elevated CO 2 increased the ratio of leaf R L to net photosynthesis at saturated light ( A max ) when plants were young and also after flowering, but the ratio of leaf R D to A max was unaffected by CO 2 levels. Leaf R N was significantly higher at the beginning but significantly lower at the end of the growing period in elevated CO 2 -grown plants. The ratio of leaf R L to R D was used to estimate the effect of light on leaf R during the day. We found that light inhibited leaf R at both CO 2 concentrations but to a lesser degree for elevated (17–24%) than for ambient (29–35%) CO 2 -grown plants, presumably because elevated CO 2 -grown plants had a higher demand for energy and carbon skeletons than ambient CO 2 -grown plants in light. Our results suggest that using the CO 2 efflux rate, determined by shading leaves during the day, as a measure for leaf R is likely to underestimate carbon loss from elevated CO 2 -grown plants.

Publication

Publisher: Springer Science and Business Media LLC

Date: 29-03-2022

DOI: 10.1038/S43017-022-00272-1

Publication

Intraspecific variation in juvenile tree growth under elevated CO₂alone and with O₃: a meta-analysis

Publisher: Oxford University Press (OUP)

Date: 15-04-2016

DOI: 10.1093/TREEPHYS/TPW026

Abstract: Atmospheric carbon dioxide (CO2) concentrations are expected to increase throughout this century, potentially fostering tree growth. A wealth of studies have examined the variation in CO2 responses across tree species, but the extent of intraspecific variation in response to elevated CO2 (eCO2) has, so far, been examined in in idual studies and syntheses of published work are currently lacking. We conducted a meta-analysis on the effects of eCO2 on tree growth (height, stem biomass and stem volume) and photosynthesis across genotypes to examine whether there is genetic variation in growth responses to eCO2 and to understand their dependence on photosynthesis. We additionally examined the interaction between the responses to eCO2 and ozone (O3), another global change agent. Most of the published studies so far have been conducted in juveniles and in Populus spp., although the patterns observed were not species dependent. All but one study reported significant genetic variation in stem biomass, and the magnitude of intraspecific variation in response to eCO2 was similar in magnitude to previous analyses on interspecific variation. Growth at eCO2 was predictable from growth at ambient CO2 (R(2) = 0.60), and relative rankings of genotype performance were preserved across CO2 levels, indicating no significant interaction between genotypic and environmental effects. The growth response to eCO2 was not correlated with the response of photosynthesis (P > 0.1), and while we observed 57.7% average increases in leaf photosynthesis, stem biomass and volume increased by 36 and 38.5%, respectively, and height only increased by 9.5%, suggesting a predominant role for carbon allocation in ultimately driving the response to eCO2 Finally, best-performing genotypes under eCO2 also responded better under eCO2 and elevated O3 Further research needs include widening the study of intraspecific variation beyond the genus Populus and examining the interaction between eCO2 and other environmental stressors. We conclude that significant potential to foster CO2-induced productivity gains through tree breeding exists, that these programs could be based upon best-performing genotypes under ambient conditions and that they would benefit from an increased understanding on the controls of allocation.

Publication

Consequences of nocturnal water loss: A synthesis of regulating factors and implications for capacitance, embolism and use in models

Publisher: Oxford University Press (OUP)

Date: 10-2014

DOI: 10.1093/TREEPHYS/TPU089

Abstract: Total daily water use is a key factor influencing the growth of many terrestrial plants, and reflects both day-time and nocturnal water fluxes. However, while nocturnal sap flow (En) and stomatal conductance (gs,n) have been reported across a range of species, ecosystems and microclimatic conditions, the regulation of these fluxes remains poorly understood. Here, we present a framework describing the role of abiotic and biotic factors in regulating En and gs,n highlighting recent developments in this field. Across ecosystems, En and gs,n generally increased with increasing soil water content and vapor pressure deficit, but the interactive effects of these factors and the potential roles of wind speed and other abiotic factors remain unclear. On average, gs,n and En are higher in broad-leaved compared with needle-leaved plants, in C3 compared with C4 plants, and in tropical compared with temperate species. We discuss the impacts of leaf age, elevated [CO2] and refilling of capacitance on night-time water loss, and how nocturnal gs,n may be included in vegetation models. Younger leaves may have higher gs,n than older leaves. Embolism refilling and recharge of capacitance may affect sap flow such that total plant water loss at night may be less than estimated solely from En measurements. Our estimates of gs,n for typical plant functional types, based on the published literature, suggest that nocturnal water loss may be a significant fraction (10-25%) of total daily water loss. Counter-intuitively, elevated [CO2] may increase nocturnal water loss. Assumptions in process-based ecophysiological models and dynamic global vegetation models that gs is zero when solar radiation is zero are likely to be incorrect. Consequently, failure to adequately consider nocturnal water loss may lead to substantial under-estimation of total plant water use and inaccurate estimation of ecosystem level water balance.

Publication

The capacity to cope with climate warming declines from temperate to tropical latitudes in two widely distributed Eucalyptus species

Publisher: Wiley

Date: 06-11-2014

DOI: 10.1111/GCB.12729

Abstract: As rapid climate warming creates a mismatch between forest trees and their home environment, the ability of trees to cope with warming depends on their capacity to physiologically adjust to higher temperatures. In widespread species, in idual trees in cooler home climates are hypothesized to more successfully acclimate to warming than their counterparts in warmer climates that may approach thermal limits. We tested this prediction with a climate‐shift experiment in widely distributed Eucalyptus tereticornis and E. grandis using provenances originating along a ~2500 km latitudinal transect (15.5–38.0°S) in eastern Australia. We grew 21 provenances in conditions approximating summer temperatures at seed origin and warmed temperatures (+3.5 °C) using a series of climate‐controlled glasshouse bays. The effects of +3.5 °C warming strongly depended on home climate. Cool‐origin provenances responded to warming through an increase in photosynthetic capacity and total leaf area, leading to enhanced growth of 20–60%. Warm‐origin provenances, however, responded to warming through a reduction in photosynthetic capacity and total leaf area, leading to reduced growth of approximately 10%. These results suggest that there is predictable intraspecific variation in the capacity of trees to respond to warming cool‐origin taxa are likely to benefit from warming, while warm‐origin taxa may be negatively affected.

Publication

Environmental and stomatal control of photosynthetic enhancement in the canopy of a sweetgum (Liquidambar styraciflua L.) plantation during 3 years of CO₂ enrichment

Publisher: Wiley

Date: 03-2002

DOI: 10.1046/J.0016-8025.2001.00816.X

Publication

Sensitivity of leaf photosynthesis to CO2 concentration is an invariant function for C3 plants: A test with experimental data and global applications

Publisher: American Geophysical Union (AGU)

Date: 06-1996

DOI: 10.1029/96GB00438

Publication

Publisher: Elsevier BV

Date: 09-2018

DOI: 10.1016/J.BUILDENV.2018.06.022

Publication

Elevated temperature is more effective than elevated [CO₂] in exposing genotypic variation in Telopea speciosissima growth plasticity: implications for woody plant populations under

Publisher: Wiley

Date: 04-07-2015

DOI: 10.1111/GCB.12990

Abstract: Intraspecific variation in phenotypic plasticity is a critical determinant of plant species capacity to cope with climate change. A long-standing hypothesis states that greater levels of environmental variability will select for genotypes with greater phenotypic plasticity. However, few studies have examined how genotypes of woody species originating from contrasting environments respond to multiple climate change factors. Here, we investigated the main and interactive effects of elevated [CO2 ] (CE ) and elevated temperature (TE ) on growth and physiology of Coastal (warmer, less variable temperature environment) and Upland (cooler, more variable temperature environment) genotypes of an Australian woody species Telopea speciosissima. Both genotypes were positively responsive to CE (35% and 29% increase in whole-plant dry mass and leaf area, respectively), but only the Coastal genotype exhibited positive growth responses to TE . We found that the Coastal genotype exhibited greater growth response to TE (47% and 85% increase in whole-plant dry mass and leaf area, respectively) when compared with the Upland genotype (no change in dry mass or leaf area). No intraspecific variation in physiological plasticity was detected under CE or TE , and the interactive effects of CE and TE on intraspecific variation in phenotypic plasticity were also largely absent. Overall, TE was a more effective climate factor than CE in exposing genotypic variation in our woody species. Our results contradict the paradigm that genotypes from more variable climates will exhibit greater phenotypic plasticity in future climate regimes.

Publication

The temperature response of leaf dark respiration in 15 provenances of Eucalyptus grandis grown in ambient and elevated CO2

Publisher: CSIRO Publishing

Date: 2017

DOI: 10.1071/FP17110

Abstract: The effects of elevated CO2 on the short-term temperature response of leaf dark respiration (R) remain uncertain for many forest tree species. Likewise, variation in leaf R among populations within tree species and potential interactive effects of elevated CO2 are poorly understood. We addressed these uncertainties by measuring the short-term temperature response of leaf R in 15 provenances of Eucalyptus grandis W. Hill ex Maiden from contrasting thermal environments grown under ambient [CO2] (aCO2 400 µmol mol–1) and elevated [CO2] (640 µmol mol–1 eCO2). Leaf R per unit area (Rarea) measured across a range of temperatures was higher in trees grown in eCO2 and varied up to 104% among provenances. However, eCO2 increased leaf dry mass per unit area (LMA) by 21%, and when R was expressed on a mass basis (i.e. Rmass), it did not differ between CO2 treatments. Likewise, accounting for differences in LMA among provenances, Rmass did not differ among provenances. The temperature sensitivity of R (i.e. Q10) did not differ between CO2 treatments or among provenances. We conclude that eCO2 had no direct effect on the temperature response of R in E. grandis, and respiratory physiology was similar among provenances of E. grandis regardless of home-climate temperature conditions.

Publication

Publisher: Copernicus GmbH

Date: 02-01-2018

DOI: 10.5194/BG-2017-526-SUPPLEMENT

Publication

Identifying areas at risk of drought‐induced tree mortality across South‐Eastern Australia

Publisher: Wiley

Date: 19-08-2020

DOI: 10.1111/GCB.15215

Publication

Interactive effects of preindustrial, current and future atmospheric CO2 concentrations and temperature on soil fungi associated with two Eucalyptus species

Publisher: Oxford University Press (OUP)

Date: 03-10-2013

DOI: 10.1111/1574-6941.12001

Abstract: Soil microbial processes have a central role in global fluxes of the key biogenic greenhouse gases and are likely to respond rapidly to climate change. Whether climate change effects on microbial processes lead to a positive or negative feedback for terrestrial ecosystem resilience is unclear. In this study, we investigated the interactive effects of [CO(2)] and temperature on soil fungi associated with faster-growing Eucalyptus saligna and slower-growing Eucalyptus sideroxylon, and fungi that colonised hyphal in-growth bags. Plants were grown in native soil under controlled soil moisture conditions, while subjecting the above-ground compartment to defined atmospheric conditions differing in CO(2) concentrations (290, 400, 650 μL L(-1)) and temperature (26 and 30 °C). Terminal restriction fragment length polymorphism and sequencing methods were used to examine effects on the structure of the soil fungal communities. There was no significant effect of host plant or [CO(2)]/temperature treatment on fungal species richness (α ersity) however, there was a significant effect on soil fungal community composition (β ersity) which was strongly influenced by eucalypt species. Interestingly, β ersity of soil fungi associated with both eucalypt species was significantly influenced by the elevated [CO(2) ]/high temperature treatment, suggesting that the combination of future predicted levels of atmospheric [CO(2)] and projected increases in global temperature will significantly alter soil fungal community composition in eucalypt forest ecosystems, independent of eucalypt species composition. These changes may arise through direct effects of changes in [CO(2)] and temperature on soil fungi or through indirect effects, which is likely the case in this study given the plant-dependent nature of our observations. This study highlights the role of plant species in moderating below-ground responses to future predicted changes to [CO(2)] and temperature and the importance of considering integrated plant-soil system responses.

Publication

Publisher: CABI

Date: 2016

DOI: 10.1079/9781780648903.0000

Publication

Woody clockworks: circadian regulation of night‐time water use in Eucalyptus globulus

Publisher: Wiley

Date: 25-06-2013

DOI: 10.1111/NPH.12382

Abstract: The role of the circadian clock in controlling the metabolism of entire trees has seldom been considered. We tested whether the clock influences nocturnal whole‐tree water use. Whole‐tree chambers allowed the control of environmental variables (temperature, relative humidity). Night‐time stomatal conductance ( g s ) and sap flow ( Q ) were monitored in 6‐ to 8‐m‐tall E ucalyptus globulus trees during nights when environmental variables were kept constant, and also when conditions varied with time. Artificial neural networks were used to quantify the relative importance of circadian regulation of g s and Q . Under a constant environment, g s and Q declined from 0 to 6 h after dusk, but increased from 6 to 12 h after dusk. While the initial decline could be attributed to multiple processes, the subsequent increase is most consistent with circadian regulation of g s and Q . We conclude that endogenous regulation of g s is an important driver of night‐time Q under natural environmental variability. The proportion of nocturnal Q variation associated with circadian regulation (23–56%) was comparable to that attributed to vapor pressure deficit variation (25–58%). This study contributes to our understanding of the linkages between molecular and cellular processes related to circadian regulation, and whole‐tree processes related to ecosystem gas exchange in the field.

Publication

Canopy position and needle age affect photosynthetic response in field-grown Pinus radiata after five years of exposure to elevated carbon dioxide partial pressure

Publisher: Oxford University Press (OUP)

Date: 08-2001

DOI: 10.1093/TREEPHYS/21.12-13.915

Abstract: Photosynthesis of tree seedlings is generally enhanced during short-term exposure to elevated atmospheric CO2 partial pressure, but longer-term studies often indicate some degree of photosynthetic adjustment. We present physiological and biochemical evidence to explain observed long-term photosynthetic responses to elevated CO2 partial pressure as influenced by needle age and canopy position. We grew Pinus radiata D. Don. trees in open-top chambers for 5 years in sandy soil at ambient (36 Pa) and elevated (65 Pa) CO2 partial pressures. The trees were well watered and exposed to natural light and ambient temperature. In the fourth year of CO2 exposure (fall 1997), when foliage growth had ceased for the year, photosynthetic down-regulation was observed in 1-year-old needles, but not in current-year needles, suggesting a reduction in carbohydrate sink strength as a result of increasing needle age (Turnbull et al. 1998). In 5-year-old trees (spring 1997), when foliage expansion was occurring, photosynthetic down-regulation was not observed, reflecting significantly large sinks for carbohydrates throughout the tree. Net photosynthesis was stimulated by 79% in trees growing in elevated CO2 partial pressure, but there was no significant effect on photosynthetic capacity or Rubisco activity and concentration. Current-year needles were more responsive to elevated CO2 partial pressure than 1-year-old needles, exhibiting larger relative increases in net photosynthesis to elevated CO2 partial pressure (98 versus 64%). Lower canopy and upper canopy leaves exhibited similar relative responses to growth in elevated CO2 partial pressure. However, needles in the upper canopy exhibited higher net photosynthesis, photosynthetic capacity, and Rubisco activity and concentration than needles in the lower canopy. Given that the ratio of mature to juvenile foliage mass in the canopy will increase as trees mature, we suggest that trees may become less responsive to elevated CO2 partial pressure with increasing age. We conclude that tree response to elevated CO2 partial pressure is based primarily on sink strength and not on the duration of exposure.

Publication

Publisher: Wiley

Date: 11-03-2004

DOI: 10.1111/J.1469-8137.2004.01046.X

Publication

Visual and hydraulic techniques produce similar estimates of cavitation resistance in woody species

Publisher: Wiley

Date: 26-07-2020

DOI: 10.1111/NPH.16746

Abstract: Hydraulic failure of the plant vascular system is a principal cause of forest die‐off under drought. Accurate quantification of this process is essential to our understanding of the physiological mechanisms underpinning plant mortality. Imaging techniques increasingly are applied to estimate xylem cavitation resistance. These techniques allow for in situ measurement of embolism formation in real time, although the benefits and trade‐offs associated with different techniques have not been evaluated in detail. Here we compare two imaging methods, microcomputed tomography (microCT) and optical vulnerability (OV), to standard hydraulic methods for measurement of cavitation resistance in seven woody species representing a ersity of major phylogenetic and xylem anatomical groups. Across the seven species, there was strong agreement between cavitation resistance values (P 50 ) estimated from visualization techniques (microCT and OV) and between visual techniques and hydraulic techniques. The results indicate that visual techniques provide accurate estimates of cavitation resistance and the degree to which xylem hydraulic function is impacted by embolism. Results are discussed in the context of trade‐offs associated with each technique and possible causes of discrepancy between estimates of cavitation resistance provided by visual and hydraulic techniques.

Publication

Age‐related decline of stand biomass accumulation is primarily due to mortality and not to reduction in NPP associated with individual tree physiology, tree growth or stand structure in a Quercus
Publisher: Wiley

Date: 04-01-2012

DOI: 10.1111/J.1365-2745.2011.01933.X

Publication

Leaf structural responses to pre-industrial, current and elevated atmospheric [CO2] and temperature affect leaf function in Eucalyptus sideroxylon

Publisher: CSIRO Publishing

Date: 2012

DOI: 10.1071/FP11238

Abstract: Leaf structure and chemistry both play critical roles in regulating photosynthesis. Yet, a key unresolved issue in climate change research is the role of changes in leaf structure in photosynthetic responses to temperature and atmospheric CO2 concentration ([CO2]), ranging from pre-industrial to future levels. We examined the interactive effects of [CO2] (290, 400 and 650 μL L–1) and temperature (ambient, ambient +4°C) on leaf structural and chemical traits that regulate photosynthesis in Eucalyptus sideroxylon A.Cunn. ex Woolls. Rising [CO2] from pre-industrial to elevated levels increased light-saturated net photosynthetic rates (Asat), but reduced photosynthetic capacity (Amax). Changes in leaf N per unit area (Narea) and the number of palisade layers accounted for 56 and 14% of the variation in Amax, respectively, associated with changes in leaf mass per area. Elevated temperature increased stomatal frequency, but did not affect Amax. Further, rising [CO2] and temperature generally did not interactively affect leaf structure or function. These results suggest that leaf Narea and the number of palisade layers are the key chemical and structural factors regulating photosynthetic capacity of E. sideroxylon under rising [CO2], whereas the lack of photosynthetic responses to elevated temperature may reflect the limited effect of temperature on leaf structure and chemistry.

Publication

Changes in composition, structure and aboveground biomass over seventy-six years (1930-2006) in the Black Rock Forest, Hudson Highlands, southeastern New York State

Publisher: Oxford University Press (OUP)

Date: 04-2008

DOI: 10.1093/TREEPHYS/28.4.537

Abstract: We sought to quantify changes in tree species composition, forest structure and aboveground forest biomass (AGB) over 76 years (1930-2006) in the deciduous Black Rock Forest in southeastern New York, USA. We used data from periodic forest inventories, published floras and a set of eight long-term plots, along with species-specific allometric equations to estimate AGB and carbon content. Between the early 1930s and 2000, three species were extirpated from the forest (American elm (Ulmus americana L.), paper birch (Betula papyrifera Marsh.) and black spruce (Picea mariana (nigra) (Mill.) BSP)) and seven species invaded the forest (non-natives tree-of-heaven (Ailanthus altissima (Mill.) Swingle) and white poplar (Populus alba L.) and native, generally southerly distributed, southern catalpa (Catalpa bignonioides Walt.), cockspur hawthorn (Crataegus crus-galli L.), red mulberry (Morus rubra L.), eastern cottonwood (Populus deltoides Bartr.) and slippery elm (Ulmus rubra Muhl.)). Forest canopy was dominated by red oak and chestnut oak, but the understory tree community changed substantially from mixed oak-maple to red maple-black birch. Density decreased from an average of 1500 to 735 trees ha(-1), whereas basal area doubled from less than 15 m(2) ha(-1) to almost 30 m(2) ha(-1) by 2000. Forest-wide mean AGB from inventory data increased from about 71 Mg ha(-1) in 1930 to about 145 Mg ha(-1) in 1985, and mean AGB on the long-term plots increased from 75 Mg ha(-1) in 1936 to 218 Mg ha(-1) in 1998. Over 76 years, red oak (Quercus rubra L.) canopy trees stored carbon at about twice the rate of similar-sized canopy trees of other species. However, there has been a significant loss of live tree biomass as a result of canopy tree mortality since 1999. Important constraints on long-term biomass increment have included insect outbreaks and droughts.

Publication

Night and day – Circadian regulation of night-time dark respiration and light-enhanced dark respiration in plant leaves and canopies

Publisher: Elsevier BV

Date: 05-2017

DOI: 10.1016/J.ENVEXPBOT.2017.01.014

Publication

Effects of age and ontogeny on photosynthetic responses of a determinate annual plant to elevated CO2 concentrations

Publisher: Wiley

Date: 03-2002

DOI: 10.1046/J.0016-8025.2001.00815.X

Publication

Adaptive plasticity in plant traits increases time to hydraulic failure under drought in a foundation tree

Publisher: Cold Spring Harbor Laboratory

Date: 20-08-2020

DOI: 10.1101/2020.08.19.258186

Abstract: The viability of forest trees, in response to climate change-associated drought, will depend on their capacity to survive through genetic adaptation and phenotypic plasticity in drought tolerance traits. Genotypes with enhanced plasticity for drought tolerance (adaptive plasticity) will have a greater ability to persist and delay the onset of hydraulic failure. Corymbia calophylla populations from two contrasting climate-origins (warm-dry and cool-wet) were grown under well-watered and chronic soil water deficit treatments in large containers. Hydraulic and allometric traits were measured and then trees were dried-down to critical levels of drought stress. Significant plasticity was detected in the warm-dry population in response to water-deficit, with adjustments in drought tolerance traits that resulted in longer dry-down times from stomatal closure to 88% loss of stem hydraulic conductance (time to hydraulic failure, THF). Plasticity was limited in the cool-wet population, indicating a significant genotype-by-environment interaction in THF. Our findings contribute information on intraspecific variation in key drought tolerance traits and THF. It highlights the need to quantify adaptive capacity in populations of forest trees facing climate change-type drought to improve predictions of forest die-back. Corymbia calophylla may benefit from assisted gene migration by introducing adaptive warm-dry populations into vulnerable cool-wet population regions.

Publication

Leaf dark respiration as a function of canopy position in Nothofagus fusca trees grown at ambient and elevated CO₂ partial pressures for 5 years

Publisher: Wiley

Date: 08-2001

DOI: 10.1046/J.0269-8463.2001.00539.X

Publication

Tree hydraulic traits are coordinated and strongly linked to climate-of-origin across a rainfall gradient

Publisher: Wiley

Date: 29-01-2018

DOI: 10.1111/PCE.13129

Abstract: Plant hydraulic traits capture the impacts of drought stress on plant function, yet vegetation models lack sufficient information regarding trait coordination and variation with climate-of-origin across species. Here, we investigated key hydraulic and carbon economy traits of 12 woody species in Australia from a broad climatic gradient, with the aim of identifying the coordination among these traits and the role of climate in shaping cross-species trait variation. The influence of environmental variation was minimized by a common garden approach, allowing us to factor out the influence of environment on phenotypic variation across species. We found that hydraulic traits (leaf turgor loss point, stomatal sensitivity to drought [P

Publication

Adaptation and acclimation both influence photosynthetic and respiratory temperature responses in Corymbia calophylla

Publisher: Oxford University Press (OUP)

Date: 28-04-2017

DOI: 10.1093/TREEPHYS/TPX047

Abstract: Short-term acclimation and long-term adaptation represent two ways in which forest trees can respond to changes in temperature. Yet, the relative contribution of thermal acclimation and adaptation to tree physiological responses to temperature remains poorly understood. Here, we grew two cool-origin and two warm-origin populations of a widespread broad-leaved evergreen tree species (Corymbia calophylla (Lindl.) K.D.Hill & L.A.S.Johnson) from a Mediterranean climate in southwestern Australia under two growth temperatures representative of the cool- and warm-edge of the species distribution. The populations selected from each thermal environment represented both high and low precipitation sites. We measured the short-term temperature response of leaf photosynthesis (A) and dark respiration (R), and attributed observed variation to acclimation, adaptation or the combination of both. We observed limited variation in the temperature optimum (Topt) of A between temperature treatments or among populations, suggesting little plasticity or genetic differentiation in the Topt of A. Yet, other aspects of the temperature response of A and R were dependent upon population and growth temperature. Under cooler growth temperatures, the population from the coolest, wettest environment had the lowest A (at 25 °C) among all four populations, but exhibited the highest A (at 25 °C) under warmer growth temperatures. Populations varied in R (at 20 °C) and the temperature sensitivity of R (i.e., Q10 or activation energy) under cool, but not warm growth temperatures. However, populations showed similar yet lower R (at 20 °C) and no differences in the temperature sensitivity of R under warmer growth temperatures. We conclude that C. calophylla populations from contrasting climates vary in physiological acclimation to temperature, which might influence how this ecologically important tree species and the forests of southwestern Australia respond to climate change.

Publication

Effects of low and elevated CO2 on C3 and C4 annuals - I. Growth and biomass allocation

Publisher: Springer Science and Business Media LLC

Date: 1995

DOI: 10.1007/BF00328894

Publication

Carbon dioxide stimulation of photosynthesis in Liquidambar styraciflua is not sustained during a 12-year field experiment

Publisher: Oxford University Press (OUP)

Date: 2015

DOI: 10.1093/AOBPLA/PLU074

Publication

Effects of low and elevated CO2 on C3 and C4 annuals - II. Photosynthesis and leaf biochemistry

Publisher: Springer Science and Business Media LLC

Date: 1995

DOI: 10.1007/BF00328895

Publication

Photosynthetic adjustment in field-grown ponderosa pine trees after six years of exposure to elevated CO2

Publisher: Oxford University Press (OUP)

Date: 04-1999

DOI: 10.1093/TREEPHYS/19.4-5.221

Abstract: Photosynthesis of tree seedlings is generally enhanced during short-term exposure to elevated atmospheric CO(2), but longer-term photosynthetic responses are often more variable because they are affected by morphological, biochemical and physiological feedback mechanisms that regulate carbon assimilation to meet sink demand. To examine biochemical and morphological factors that might regulate the long-term photosynthetic response of field-grown trees to elevated CO(2), we grew ponderosa pine (Pinus ponderosa Dougl. ex Laws.) trees in open-top chambers for six years in native soil at ambient CO(2) (35 Pa) and elevated CO(2) (70 Pa) at a site near Placerville, CA. Trees were well watered and exposed to natural light and ambient temperature. At the end of the sixth growing season at elevated CO(2), net photosynthesis was enhanced 53%, despite reductions in photosynthetic capacity. The positive net photosynthetic response to elevated CO(2) reflected greater relative increases in Rubisco sensitivity compared with the decreases resulting from biochemical adjustments. Analyses of net photosynthetic rate versus internal CO(2) partial pressure curves indicated that reductions in photosynthetic capacity in response to elevated CO(2) were the result of significant reductions in maximum photosynthetic rate (20%), Rubisco carboxylation capacity (36%), and electron transport capacity (21%). Decreased photosynthetic capacity was accompanied by reductions in various photosynthetic components, including total chlorophyll (24%), Rubisco protein content (38%), and mass-based leaf nitrogen concentration (14%). Net photosynthesis was unaffected by morphological adjustments because there was no change in leaf mass per unit area at elevated CO(2). An apparent positive response of photosynthetic adjustment in the elevated CO(2) treatment was the redistribution of N within the photosynthetic system to balance Rubisco carboxylation and electron transport capacities. We conclude that trees, without apparent limitations to root growth, may exhibit photosynthetic adjustment responses in the field after long-term exposure to elevated CO(2).

Publication

Intraspecific variation in plant responses to atmospheric CO2, temperature and water availability

Publisher: Springer International Publishing

Date: 2021

DOI: 10.1007/978-3-030-64926-5_6

Publication

Differential daytime and night‐time stomatal behavior in plants from North American deserts

Publisher: Wiley

Date: 20-02-2012

DOI: 10.1111/J.1469-8137.2012.04068.X

Abstract: Night-time stomatal conductance (g(night)) occurs in many ecosystems, but the g(night) response to environmental drivers is relatively unknown, especially in deserts. Here, we conducted a Bayesian analysis of stomatal conductance (g) (N=5013) from 16 species in the Sonoran, Chihuahuan, Mojave and Great Basin Deserts (North America). We partitioned daytime g (g(day)) and g(night) responses by describing g as a mixture of two extreme (dark vs high light) behaviors. Significant g(night) was observed across 15 species, and the g(night) and g(day) behavior differed according to species, functional type and desert. The transition between extreme behaviors was determined by light environment, with the transition behavior differing between functional types and deserts. Sonoran and Chihuahuan C(4) grasses were more sensitive to vapor pressure difference (D) at night and soil water potential (Ψ(soil)) during the day, Great Basin C(3) shrubs were highly sensitive to D and Ψ(soil) during the day, and Mojave C(3) shrubs were equally sensitive to D and Ψ(soil) during the day and night. Species were split between the exhibition of isohydric or anisohydric behavior during the day. Three species switched from anisohydric to isohydric behavior at night. Such behavior, combined with differential D, Ψ(soil) and light responses, suggests that different mechanisms underlie g(day) and g(night) regulation.

Publication

Photosynthesis and seed production under water-deficit conditions in transgenic tobacco plants that overexpress an Arabidopsis ascorbate peroxidase gene

Publisher: Wiley

Date: 07-2003

DOI: 10.2135/CROPSCI2003.1477

Publication

Capacity of old trees to respond to environmental change

Publisher: Wiley

Date: 23-10-2008

DOI: 10.1111/J.1744-7909.2008.00746.X

Abstract: Atmospheric carbon dioxide [CO2] has increased dramatically within the current life spans of long-lived trees and old forests. Consider that a 500-year-old tree in the early twenty-first century has spent 70% of its life growing under pre-industrial levels of [CO2], which were 30% lower than current levels. Here we address the question of whether old trees have already responded to the rapid rise in [CO2] occurring over the past 150 years. In spite of limited data, aging trees have been shown to possess a substantial capacity for increased net growth after a period of post-maturity growth decline. Observations of renewed growth and physiological function in old trees have, in some instances, coincided with Industrial Age increases in key environmental resources, including [CO2], suggesting the potential for continued growth in old trees as a function of continued global climate change.

Publication

Effects of a Heat Wave on Nocturnal Stomatal Conductance in Eucalyptus camaldulensis

Publisher: MDPI AG

Date: 03-06-2018

DOI: 10.3390/F9060319

Publication

Functional Plant Biology: Forword

Publisher: CSIRO Publishing

Date: 2008

DOI: 10.1071/FPV35N6_FO

Publication

Elevated carbon dioxide alters hydrocarbon emissions and flavor in onion

Publisher: SAE International

Date: 19-07-2004

DOI: 10.4271/2004-01-2299

Publication

Repeated extreme heatwaves result in higher leaf thermal tolerances and greater safety margins

Publisher: Wiley

Date: 30-08-2021

DOI: 10.1111/NPH.17640

Abstract: The frequency and severity of heatwave events are increasing, exposing species to conditions beyond their physiological limits. Species respond to heatwaves in different ways, however it remains unclear if plants have the adaptive capacity to successfully respond to hotter and more frequent heatwaves. We exposed eight tree populations from two climate regions grown under cool and warm temperatures to repeated heatwave events of moderate (40°C) and extreme (46°C) severity to assess adaptive capacity to heatwaves. Leaf damage and maximum quantum efficiency of photosystem II ( F v / F m ) were significantly impacted by heatwave severity and growth temperatures, respectively populations from a warm‐origin avoided damage under moderate heatwaves compared to those from a cool‐origin, indicating a degree of local adaptation. We found that plasticity to heatwave severity and repeated heatwaves contributed to enhanced thermal tolerance and lower leaf temperatures , leading to greater thermal safety margins (thermal tolerance minus leaf temperature) in a second heatwave. Notably, while we show that adaptation and physiological plasticity are important factors affecting plant adaptive capacity to thermal stress, plasticity of thermal tolerances and thermal safety margins provides the opportunity for trees to persist among fluctuating heatwave exposures.

Publication

Warming Reduces Net Carbon Gain and Productivity in Medicago sativa L. and Festuca arundinacea

Publisher: MDPI AG

Date: 19-10-2020

DOI: 10.3390/AGRONOMY10101601

Abstract: High temperature stress imposes constraints on the productivity of agricultural systems, such as pastures, and predicted increases in global temperatures are set to exacerbate these limitations. Here, we sought to understand the impact of warmer growth temperature on gas exchange and net primary productivity for two widely cultivated pasture species. We grew a C3 legume, Medicago sativa (lucerne), and a C3 grass, Festuca arundinacea Schreb. (tall fescue), in a climate-controlled facility exposed to two temperature treatments (ambient: 26 °C, aT elevated: 30 °C, eT). Soil water was maintained at non-limiting conditions in both temperature treatments to control for the confounding effects of warming on soil moisture. We found that warming reduced photosynthetic capacity and increased leaf dark respiration (Rdark) in lucerne, while tall fescue showed little physiological change at the leaf level, but increased ecosystem respiration (Reco). Growth temperature had no significant impact on the thermal optimum of photosynthesis (Topt) or water use efficiency in either species. Both species exhibited significant reductions in productivity with warming lucerne had greater reductions in shoot biomass, while tall fescue had greater reductions in root biomass. Our results highlight the potential for significant declines in pasture productivity associated with even modest increases in average temperature and highlights the need for suitable management strategies and implementation of more heat-resistant cultivars. Improvements in photosynthetic performance for greater heat tolerance in lucerne, and traits associated with biomass allocation and root performance at higher temperatures in tall fescue, should be the focus for improving high temperature resistance in these plant species.

Publication

Compensation for PSII photoinactivation by regulated non-photochemical dissipation influences the impact of photoinactivation on electron transport and CO2 assimilation

Publisher: Oxford University Press (OUP)

Date: 04-2006

DOI: 10.1093/PCP/PCJ010

Abstract: The extent to which PSII photoinactivation affects electron transport (PhiPSII) and CO2 assimilation remains controversial, in part because it frequently occurs alongside inactivation of other components of photosynthesis, such as PSI. By manipulating conditions (darkness versus low light) after a high light/low temperature treatment, we examined the influence of different levels of PSII inactivation at the same level of PSI inactivation on PhiPSII and CO2 assimilation for Arabidopsis. Furthermore, we compared PhiPSII at high light and optimum temperature for wild-type Arabidopsis and a mutant (npq4-1) with impaired capacities for energy dissipation. Levels of PSII inactivation typical of natural conditions (< 50%) were not associated with decreases in PhiPSII and CO2 assimilation at photon flux densities (PFDs) above 150 micromol m(-2) s(-1). At higher PFDs, the light energy being absorbed was in excess of the energy that could be utilized by downstream processes. Arabidopsis plants downregulate PSII activity to dissipate such excess in accordance with the level of PSII photoinactivation that also serves to dissipate absorbed energy. Therefore, the overall levels of non-photochemical dissipation and the efficiency of photochemistry were not affected by PSII inactivation at high PFD. Under low PFD conditions, such compensation is not necessary, because the amount of light energy absorbed is not in excess of that needed for photochemistry, and inactive PSII complexes are dissipating energy. We conclude that moderate photoinactivation of PSII complexes will only affect plant performance when periods of high PFD are followed by periods of low PFD.

Publication

Comparison of spectrophotometric and radioisotopic methods for the assay of Rubisco in ozone-treated plants

Publisher: Wiley

Date: 10-1997

DOI: 10.1034/J.1399-3054.1997.1010221.X

Publication

Sap flow rates and sapwood density are critical factors in within- and between-tree variation in CO2 efflux from stems of mature Dacrydium cupressinum trees

Publisher: Wiley

Date: 16-06-2005

DOI: 10.1111/J.1469-8137.2005.01478.X

Abstract: Measurements of CO2 efflux from stems and branches, sap velocity, and respiratory activity of excised wood cores were conducted in Dacrydium cupressinum trees that differed in diameter, age, and canopy emergence. The objective of this study was to determine if consistent linkages exist among respiratory production of CO2 within stems, xylem transport of CO2, and the rate of CO2 diffusing from stem surfaces. Stem CO2 efflux was depressed during periods of sap flow compared with the efflux rate expected for a given stem temperature and was positively correlated with sapwood density. By contrast, no significant relationships were observed between CO2 efflux and the respiratory activity of wood tissues. Between 86 and 91% of woody tissue respiration diffused to the atmosphere over a 24-h period. However, at certain times of the day, xylem transport and internal storage of CO2 may account for up to 13-38% and 12-18%, respectively, of woody tissue respiration. These results demonstrate that differences in sap flow rates and xylem anatomy are critically important for explaining within- and between-tree variation in CO2 efflux from stems.

Publication

Diel water movement between parenchyma and chlorenchyma of two desert CAM plants under dry and wet conditions

Publisher: Wiley

Date: 05-1991

DOI: 10.1111/J.1365-3040.1991.TB00950.X

Publication

Interactive effects of elevated CO₂, temperature and extreme weather events on soil nitrogen and cotton productivity indicate increased variability of cotton production under future climate regimes

Publisher: Elsevier BV

Date: 08-2017

DOI: 10.1016/J.AGEE.2017.06.004

Publication

The effect of elevated atmospheric [CO2] and increased temperatures on an older and modern cotton cultivar

Publisher: CSIRO Publishing

Date: 2017

DOI: 10.1071/FP17165

Abstract: Changes in atmospheric [CO2], temperature and precipitation under projected climate change scenarios may have significant impacts on the physiology and yield of cotton. Understanding the implications of integrated environmental impacts on cotton is critical for developing cotton systems that are resilient to stresses induced by climate change. The objective of this study was to quantify the physiological and growth capacity of two cotton cultivars under current and future climate regimes. This experiment compared the early-season growth and physiological response of an older (DP16, released in the 1970s) and a modern (Sicot 71BRF, released in 2008) cotton cultivar grown in ambient and elevated atmospheric [CO2] (CA, 400 µL L–1 and CE, 640 µL L–1 respectively) and two temperature (TA, 28/17°C and TE, 32/21°C, day/night, respectively) treatments under well-watered conditions. CE increased biomass and photosynthetic rates compared with CA, and TE increased plant biomass. Although limited by the comparison of one older and one modern cultivar, our results suggest that substantial potential may exist to increase breeding selection of cotton cultivars that are responsive to both TE and CE.

Publication

Photosynthetic and biochemical responses of four subtropical tree seedlings to reduced dry season and increased wet season precipitation and variable N deposition

Publisher: Oxford University Press (OUP)

Date: 26-09-2023

DOI: 10.1093/TREEPHYS/TPAD114

Publication

Light inhibition of leaf respiration in field-grown Eucalyptus saligna in whole-tree chambers under elevated atmospheric CO2 and summer drought

Publisher: Wiley

Date: 14-12-2011

DOI: 10.1111/J.1365-3040.2011.02465.X

Abstract: We investigated whether the degree of light inhibition of leaf respiration (R) differs among large Eucalyptus saligna grown in whole-tree chambers and exposed to present and future atmospheric [CO(2) ] and summer drought. Associated with month-to-month changes in temperature were concomitant changes in R in the light (R(light) ) and darkness (R(dark) ), with both processes being more temperature dependent in well-watered trees than under drought. Overall rates of R(light) and R(dark) were not significantly affected by [CO(2) ]. By contrast, overall rates of R(dark) (averaged across both [CO(2) ]) were ca. 25% lower under drought than in well-watered trees. During summer, the degree of light inhibition of leaf R was greater in droughted (ca. 80% inhibition) than well-watered trees (ca. 50% inhibition). Notwithstanding these treatment differences, an overall positive relationship was observed between R(light) and R(dark) when data from all months/treatments were combined (R(2) = 0.8). Variations in R(light) were also positively correlated with rates of Rubisco activity and nitrogen concentration. Light inhibition resulted in a marked decrease in the proportion of light-saturated photosynthesis respired (i.e. reduced R/A(sat) ). Collectively, these results highlight the need to account for light inhibition when assessing impacts of global change drivers on the carbon economy of tree canopies.

Publication

Seasonal microbial and nutrient responses during a 5-year reduction in the daily temperature range of soil in a Chihuahuan Desert ecosystem

Publisher: Springer Science and Business Media LLC

Date: 21-09-2016

DOI: 10.1007/S00442-015-3452-X

Publication

Elevated [CO₂] does not ameliorate the negative effects of elevated temperature on drought‐induced mortality in Eucalyptus radiata seedlings

Publisher: Wiley

Date: 13-02-2014

DOI: 10.1111/PCE.12260

Abstract: It has been reported that elevated temperature accelerates the time-to-mortality in plants exposed to prolonged drought, while elevated [CO(2)] acts as a mitigating factor because it can reduce stomatal conductance and thereby reduce water loss. We examined the interactive effects of elevated [CO(2)] and temperature on the inter-dependent carbon and hydraulic characteristics associated with drought-induced mortality in Eucalyptus radiata seedlings grown in two [CO(2)] (400 and 640 μL L(-1)) and two temperature (ambient and ambient +4 °C) treatments. Seedlings were exposed to two controlled drying and rewatering cycles, and then water was withheld until plants died. The extent of xylem cavitation was assessed as loss of stem hydraulic conductivity. Elevated temperature triggered more rapid mortality than ambient temperature through hydraulic failure, and was associated with larger water use, increased drought sensitivities of gas exchange traits and earlier occurrence of xylem cavitation. Elevated [CO(2)] had a negligible effect on seedling response to drought, and did not ameliorate the negative effects of elevated temperature on drought. Our findings suggest that elevated temperature and consequent higher vapour pressure deficit, but not elevated [CO(2)], may be the primary contributors to drought-induced seedling mortality under future climates.

Publication

The ecology of Bactrocera tryoni (Diptera: Tephritidae): What do we know to assist pest management?

Publisher: Wiley

Date: 02-11-2011

DOI: 10.1111/J.1744-7348.2010.00448.X

Publication

Drought increases heat tolerance of leaf respiration in Eucalyptus globulus saplings grown under both ambient and elevated atmospheric [CO2] and temperature

Publisher: Oxford University Press (OUP)

Date: 09-09-2014

DOI: 10.1093/JXB/ERU367

Publication

Drought tolerance of Hakea species (Proteaceae) from a range of biomes and life-histories predicted by climatic niche

Publisher: Cold Spring Harbor Laboratory

Date: 02-09-2020

DOI: 10.1101/2020.09.01.276931

Abstract: Extreme drought conditions across the globe are impacting bio ersity with serious implications for the persistence of native species. However, quantitative data on drought tolerance is not available for erse flora to inform conservation management. We quantified physiological drought tolerance in the erse Hakea genus (Proteaceae) to test predictions based on climatic-origin, life history and functional traits. We s led terminal branches of replicate plants of 16 species in a common garden. Xylem cavitation was induced in branches under varying water potential (tension) in a centrifuge and the tension generating 50% loss of conductivity (stem P50) was characterized as a metric for drought tolerance. The same branches were used to estimate plant functional traits, including wood density, specific leaf area, and Huber value (sap flow area to leaf area ratio). There was significant variation in stem P50 among species, which was negatively associated with the species climate-origin (rainfall and aridity). Drought tolerance did not differ among life histories however, a drought avoidance strategy with terete leaf form and greater Huber value may be important for species to colonize and persist in the arid biome. Our findings will contribute to future prediction of species vulnerability to drought and adaptive management under climate change.

Publication

Resource pulses in arid environments - Patterns of rain, patterns of life

Publisher: Wiley

Date: 24-01-2003

DOI: 10.1046/J.1469-8137.2003.00672.X

Publication

Warming alters the positive impact of elevated CO2 concentration on cotton growth and physiology during soil water deficit

Publisher: CSIRO Publishing

Date: 2016

DOI: 10.1071/FP16189

Abstract: Alterations in climate factors such as rising CO2 concentration ([CO2]), warming and reduced precipitation may have significant impacts on plant physiology and growth. This research investigated the interactive effects of elevated [CO2], warming and soil water deficit on biomass production, leaf-level physiological responses and whole-plant water use efficiency (WUEP) in cotton (Gossypium hirsutum L.). Cotton was grown in the glasshouse under two [CO2] treatments (CA, 400 µL L–1 CE, 640 µL L–1) and two temperature treatments (TA, 28°C : 17°C day : night TE, 32°C : 21°C day : night). Plants were subjected to two progressive water deficit cycles, with a 5-day recovery period between the water deficit periods. CE increased vegetative biomass and photosynthetic rates, and decreased stomatal conductance in TA however, these responses to CE were not evident under TE. CE increased whole-plant water loss under TA, but increased WUEp, whereas increased whole-plant water loss in TE decreased WUEp regardless of atmospheric [CO2]. CE may provide some positive growth and physiological benefits to cotton at TA if sufficient water is available but CE will not mitigate the negative effects of rising temperature on cotton growth and physiology in future environments.

Publication

Leaf silicification provides herbivore defence regardless of the extensive impacts of water stress

Publisher: Wiley

Date: 21-04-2021

DOI: 10.1111/1365-2435.13794

Abstract: Altered precipitation patterns due to climate change are likely to impose water‐deficit stress in plants resulting in changes to specific leaf mass, leaf water content and chemical defences that may impact herbivorous arthropods. Grasses, in particular, accumulate large concentrations of silicon (Si) which provides physical defence against herbivores. Although Si uptake by plants may be affected by water availability, very few studies have investigated the combined effect of water‐deficit stress and Si on insect herbivore performance. We grew tall fescue Festuca arundinacea Schreb. hydroponically, with and without Si, and half of the plants were treated with 20% polyethylene glycol (PEG) to impose osmotic stress. In all, 11 leaf traits (physiological, chemical and structural) were measured, silicified phytoliths on the leaf surface were visualised using scanning electron microscopy (SEM) in conjunction with X‐ray mapping, and plants were exposed to a chewing insect herbivore [ Helicoverpa armigera Hübner (Lepidoptera: Noctuidae)]. Although osmotic stress was associated with changes to leaf physiological and chemical traits, including increased specific leaf mass, decreased leaf relative water content and increased leaf nitrogen (N), there was no significant effect on H. armigera relative growth rate (RGR). However, Si reduced RGR of H. armigera by 80%–98% while generating few changes to physiological and chemical leaf traits. Instead, the decline in RGR with Si was associated with changes to leaf structural traits, in particular, a greater density of silicified phytoliths on the leaf surface. Comparison of effect sizes indicated that leaf traits were primarily affected by osmotic stress but not Si, and that herbivore RGR was strongly negatively affected by Si but not osmotic stress. There was no interactive effect between the osmotic stress and Si treatments on H. armigera RGR or plant traits except for leaf nitrogen and phenolic concentrations. This study provides further support that Si may prove to be beneficial to plants against chewing insect pests and remains robust regardless of water‐deficit stress conditions. A free Plain Language Summary can be found within the Supporting Information of this article.

Publication

Traits and trade-offs in whole-tree hydraulic architecture along the vertical axis of Eucalyptus grandis

Publisher: Oxford University Press (OUP)

Date: 2018

DOI: 10.1093/AOB/MCX137

Publication

Whole-tree chambers for elevated atmospheric CO2 experimentation and tree scale flux measurements in south-eastern Australia: The Hawkesbury Forest Experiment

Publisher: Elsevier BV

Date: 15-07-2010

DOI: 10.1016/J.AGRFORMET.2010.03.001

Publication

Flavonol content and composition of spring onions grown hydroponically or in potting soil

Publisher: Elsevier BV

Date: 11-2005

DOI: 10.1016/J.JFCA.2004.06.009

Publication

Atmospheric CO2 enrichment increases growth and photosynthesis of Pinus taeda: A 4 year experiment in the field

Publisher: Wiley

Date: 09-1997

DOI: 10.1046/J.1365-3040.1997.D01-140.X

Publication

Mesophyll conductance in two cultivars of wheat grown in glacial to super-elevated CO2 concentrations

Publisher: Oxford University Press (OUP)

Date: 07-07-2021

DOI: 10.1093/JXB/ERAB320

Abstract: Mesophyll conductance (gm) is an important factor limiting photosynthesis. However, gm response to long-term growth in variable [CO2] is not well understood, particularly in crop plants. Here, we grew two cultivars of wheat (Halberd and Cranbrook), known to differ in gm under current environmental conditions, in four [CO2] treatments: glacial (206 μmol mol−1), pre-industrial (344 μmol mol−1), current ambient (489 μmol mol−1), and super-elevated (1085 μmol mol−1), and two water treatments (well-watered and moderate water limitation), to develop an evolutionary and future climate perspective on gm control of photosynthesis and water-use efficiency (WUE). In the two wheat genotypes, gm increased with rising [CO2] from glacial to ambient [CO2], but declined at super-elevated [CO2]. The responses of gm to different growth [CO2] also depend on water stress however, the specific mechanism of gm response to [CO2] remains unclear. Although gm and gm/gsc (mesophyll conductance/stomatal conductance) were strongly associated with the variability of photosynthetic rates (A) and WUE, we found that plants with higher gm may increase A without increasing gsc, which increased WUE. These results may be useful to inform plant breeding programmes and cultivar selection for Australian wheat under future environmental conditions.

Publication

Water, nitrogen and phosphorus use efficiencies of four tree species in response to variable water and nutrient supply

Publisher: Springer Science and Business Media LLC

Date: 31-03-2016

DOI: 10.1007/S11104-016-2873-6

Publication

Sustainable Protected Cropping: A Case Study of Seasonal Impacts on Greenhouse Energy Consumption during Capsicum Production

Publisher: MDPI AG

Date: 30-08-2020

DOI: 10.3390/EN13174468

Abstract: Sustainable food production in protected cropping is increasing rapidly in response to global climate change and population growth. However, there are significant knowledge gaps regarding energy consumption while achieving optimum environmental conditions for greenhouse crop production. A capsicum crop cultivated in a high-tech greenhouse facility in Australia was analysed in terms of relationships between key environmental variables and the comparative analysis of energy consumption during different seasons. We showed that daily energy consumption varied due to the seasonal nature of the external environment and maintenance of optimal growing temperatures. Total power consumption reported throughout the entire crop cycle for heating (gas hot water system) and cooling (pad and fan) was 12,503 and 5183 kWh, respectively hence, heating consumed ca. 70% of the total energy requirement over the 8-month growing period (early spring to late autumn) in the greenhouse facility. Regressions of daily energy consumption within each season, designated either predominantly for heating or cooling, indicated that energy consumption was 14.62 kWh per 1 °C heating and 2.23 kWh per 1 °C cooling. Therefore, changing the planting date to late spring is likely to significantly reduce heating energy costs for greenhouse capsicum growers in Australia. The findings will provide useful guidelines to maximise the greenhouse production of capsicum with better economic return by taking into consideration the potential optimal energy saving strategy during different external environment conditions and seasons.

Publication

Interactive effects of pre-industrial, current and future [CO2] and temperature on an insect herbivore of Eucalyptus

Publisher: Springer Science and Business Media LLC

Date: 02-10-2012

DOI: 10.1007/S00442-012-2467-9

Abstract: Both atmospheric [CO2] and average surface temperatures are predicted to increase with potentially different, additive or opposing, effects on leaf quality and insect herbivore activity. Few studies have directly measured the interactive effects of concurrent changes in [CO2] and temperature on insect herbivores. None have done so over the entire developmental period of a tree-feeding insect, and none have compared responses to low pre-industrial [CO2] and present day [CO2] to estimate responses to future increases. Eucalypt herbivores may be particularly sensitive to climate-driven shifts in plant chemistry, as eucalypt foliage is naturally low in [N]. In this study, we assessed the development of the eucalypt herbivore Doratifera quadriguttata exposed concurrently to variable [CO2] (290, 400, 650 μmol mol(-1)) and temperature (ambient, ambient +4 °C) on glasshouse-grown Eucalyptus tereticornis. Overall, insects performed best on foliage grown at pre-industrial [CO2], indicating that modern insect herbivores have already experienced nutritional shifts since industrialisation. Rising [CO2] increased specific leaf mass and leaf carbohydrate concentration, subsequently reducing leaf [N]. Lower leaf [N] induced compensatory feeding and impeded insect performance, particularly by prolonging larval development. Importantly, elevated temperature d ened the negative effects of rising [CO2] on larval performance. Therefore, rising [CO2] over the past 200 years may have reduced forage quality for eucalypt insects, but concurrent temperature increases may have partially compensated for this, and may continue to do so in the future. These results highlight the importance of assessing plant-insect interactions within the context of multiple climate-change factors because of the interactive and potentially opposing effects of different factors within and between trophic levels.

Publication

Impact of variable [CO 2] and temperature on water transport structure-function relationships in Eucalyptus

Publisher: Oxford University Press (OUP)

Date: 27-06-2011

DOI: 10.1093/TREEPHYS/TPR049

Abstract: Nearly 30 years ago, Whitehead and Jarvis and Whitehead et al. postulated an elegant mechanistic explanation for the observed relationship between tree hydraulic structure and function, hypothesizing that structural adjustments promote physiological homeostasis. To date, this framework has been nearly completely overlooked with regard to varying atmospheric carbon dioxide ([CO(2)]). Here, we evaluated Whitehead's hypothesis of leaf water potential (Ψ(l)) homeostasis in faster-growing (Eucalyptus saligna) and slower-growing (Eucalyptus sideroxylon) tree saplings grown under three [CO(2)] (pre-industrial, current and future) and two temperature (ambient and ambient + 4°C) treatments. We tested for relationships between physiological (stomatal conductance and Ψ(l)) and structural (leaf and sapwood areas (A(l), A(s)), height (h), xylem conductivity (k(s))) plant variables as a function of the [CO(2)] and temperature treatments to assess whether structural variables adjusted to maintain physiological homeostasis. Structural components (A(l), A(s), h) generally increased with [CO(2)] or temperature, while g(s) was negatively correlated with [CO(2)]. Contrary to Whitehead's hypothesis, Ψ(l) did not exhibit homeostasis in either species elevated temperatures were associated with more negative Ψ(l) in faster-growing E. saligna, and less negative Ψ(l) in slower-growing E. sideroxylon. Moreover, in idual structural variables were generally uncorrelated with Ψ(l). However, across both species, the integrated hydraulic property of leaf specific hydraulic conductance (K(l)) was positively correlated with an independent calculation of K(l) determined exclusively from leaf physiological variables. These results suggest that physiological homeostasis may not apply to saplings exposed to global change drivers including [CO(2)] and temperature. Nevertheless, Whitehead et al.'s formulation identified K(l) as a sensitive measure of plant structural-physiological co-variation across species.

Publication

A hierarchical Bayesian approach for estimation of photosynthetic parameters of C3 plants

Publisher: Wiley

Date: 05-11-2009

DOI: 10.1111/J.1365-3040.2009.02029.X

Abstract: We describe a hierarchical Bayesian (HB) approach to fitting the Farquhar et al.model of photosynthesis to leaf gas exchange data. We illustrate the utility of this approach for estimating photosynthetic parameters using data from desert shrubs. Unique to the HB method is its ability to simultaneously estimate plant- and species-level parameters, adjust for peaked or non-peaked temperature dependence of parameters, explicitly estimate the 'critical' intracellular [CO(2)] marking the transition between ribulose 1.5-bisphosphate carboxylase/oxygenase (Rubisco) and ribulose-1,5-bisphosphate (RuBP) limitations, and use both light response and CO(2) response curve data to better inform parameter estimates. The model successfully predicted observed photosynthesis and yielded estimates of photosynthetic parameters and their uncertainty. The model with peaked temperature responses fit the data best, and inclusion of light response data improved estimates for day respiration (R(d)). Species differed in R(d25) (R(d) at 25 degrees C), maximum rate of electron transport (J(max25)), a Michaelis-Menten constant (K(c25)) and a temperature dependence parameter (DeltaS). Such differences could potentially reflect differential physiological adaptations to environmental variation. Plants differed in R(d25), J(max25), mesophyll conductance (g(m25)) and maximum rate of Rubisco carboxylation (V(cmax25)). These results suggest that plant- and species-level variation should be accounted for when applying the Farquhar et al. model in an inferential or predictive framework.

Publication

Photosynthetic responses of cottonwood seedlings grown in glacial through future atmospheric [CO2] vary with phosphorus supply

Publisher: Oxford University Press (OUP)

Date: 29-09-2010

DOI: 10.1093/TREEPHYS/TPQ077

Abstract: Plants often exhibit proportionately larger photosynthetic responses to the transition from glacial to modern [CO(2)] than from modern to future [CO(2)]. Although this pattern may reflect increased nutrient demand with increasing [CO(2)], few studies have examined the role of nutrient supply in regulating responses to the range of [CO(2)] from glacial to future [CO(2)]. In this study, we examined the effects of P supply (0.004-0.5 mM) on photosynthetic responses of Populus deltoides (cottonwood) seedlings to glacial (200 micromol mol(-1)), modern (350 µmol mol(-1)) and future (700 micromol mol(-1)) [CO(2)]. The A(sat) (light-saturated net photosynthetic rates at the growth [CO(2)]) response to future [CO(2)] decreased with decreasing P supply such that there was no response at the lowest P supply. However, P supply did not affect A(sat) responses to an increase from glacial to modern [CO(2)]. Photosynthetic capacity [e.g., final rubisco activity, apparent, maximal Rubisco-limited rate of photosynthesis (V(cmax)), apparent, maximal electron transport-limited rate of photosynthesis (J(max))], stomatal conductance (g(s)) and leaf P generally increased with increasing P supply but decreased with increasing [CO(2)]. Measures of carbohydrate sink capacity (e.g., leaf mass per unit leaf area, leaf starch) increased with both increasing P supply and increasing [CO(2)]. Changes in V(cmax) and g(s) together accounted for 78% of the variation in A(sat) among [CO(2)] and P treatments, suggesting significant biochemical and stomatal controls on photosynthesis. However, A(sat) responses to increasing [CO(2)] did not reflect the changes in the carbohydrate sink capacity. These results have important implications because low P already constrains responses to increasing [CO(2)] in many ecosystems, and our results suggest that the P demand will increasingly affect A(sat) in cottonwood as [CO(2)] continues to increase.

Publication

A Plant-Soil-Atmosphere Microcosm for Tracing Radiocarbon from Photosynthesis through Methanogenesis

Publisher: Wiley

Date: 05-1999

DOI: 10.2136/SSSAJ1999.03615995006300030033X

Publication

Responses of respiration in the light to warming in field‐grown trees: a comparison of the thermal sensitivity of the Kok and Laisk methods

Publisher: Wiley

Date: 30-11-2018

DOI: 10.1111/NPH.15566

Abstract: The Kok and Laisk techniques can both be used to estimate light respiration R

Publication

Circadian Regulation Does Not Optimize Stomatal Behaviour

Publisher: MDPI AG

Date: 25-08-2020

DOI: 10.3390/PLANTS9091091

Abstract: The circadian clock is a molecular timer of metabolism that affects the diurnal pattern of stomatal conductance (gs), amongst other processes, in a broad array of plant species. The function of circadian gs regulation remains unknown and here, we test whether circadian regulation helps to optimize diurnal variations in stomatal conductance. We subjected bean (Phaseolus vulgaris) and cotton (Gossypium hirsutum) canopies to fixed, continuous environmental conditions of photosynthetically active radiation, temperature, and vapour pressure deficit (free-running conditions) over 48 h. We modelled gs variations in free-running conditions to test for two possible optimizations of stomatal behaviour under circadian regulation: (i) that stomata operate to maintain constant marginal water use efficiency or (ii) that stomata maximize C net gain minus the costs or risks of hydraulic damage. We observed that both optimization models predicted gs poorly under free-running conditions, indicating that circadian regulation does not directly lead to stomatal optimization. We also demonstrate that failure to account for circadian variation in gs could potentially lead to biased parameter estimates during calibrations of stomatal models. More broadly, our results add to the emerging field of plant circadian ecology, where circadian controls may partially explain leaf-level patterns observed in the field.

Publication

Impact of industrial-age climate change on the relationship between water uptake and tissue nitrogen in eucalypt seedlings

Publisher: CSIRO Publishing

Date: 2013

DOI: 10.1071/FP12130

Abstract: This study explored reductions in tissue nitrogen concentration ([N]) at elevated CO2 concentrations ([CO2]), and changes in plant water and N uptake. Eucalyptus saligna Sm. seedlings were grown under three [CO2] levels (preindustrial (280 μL L–1), current (400 μL L–1) or projected (640 μL L–1)) and two air temperatures (current, (current + 4°C)). Gravimetric water use, leaf gas exchange and tissue dry mass and %N were determined. Solid-state 15N-NMR spectroscopy was used for determining the partitioning of N chemical groups in the dry matter fractions. Water use efficiency (WUE) improved with increasing [CO2] at ambient temperature, but strong leaf area and weak reductions in transpiration rates led to greater water use at elevated [CO2]. High temperature increased plant water use, such that WUE was not significantly stimulated by increasing [CO2] at high temperature. Total N uptake increased with increasing [CO2] but not temperature, less than the increase recorded for plant biomass. Tissue [N] decreased with rising [CO2] and at high temperature, but N use efficiency increased with rising [CO2]. Total N uptake was positively correlated with total water use and root biomass under all treatments. Growth [CO2] and temperature did not affect the partitioning of 15N among the N chemical groups. The reductions of tissue [N] with [CO2] and temperature were generic, not specific to particular N compounds. The results suggest that reductions in tissue [N] are caused by changes in root N uptake by mass flow due to altered transpiration rates at elevated [CO2] and temperature.

Publication

Drought tolerance traits do not vary across sites differing in water availability in Banksia serrata (Proteaceae)

Publisher: CSIRO Publishing

Date: 2019

DOI: 10.1071/FP18238

Abstract: Interspecific variation in plant hydraulic traits plays a major role in shaping species distributions across climates, yet variation within species is poorly understood. Here we report on intraspecific variation of hydraulic traits in Banksia serrata (L.f.) s led from three sites characterised by contrasting climates (warm-wet, warm-dry and cool-wet). Hydraulic characteristics including vulnerability to embolism, hydraulic conductance, pressure-volume traits and key morphological traits were measured. Vulnerability to embolism in leaf and stem, defined by the water potential inducing 50 and 88% loss of hydraulic conductivity (P50 and P88 respectively), did not differ across sites. However, plants from the warm-dry environment exhibited higher stem conductivity (Ks) than the cool-wet environment. Leaf turgor loss point (TLP) did not vary among sites, but warm-dry site plants showed lower leaf capacitance (C*FT) and higher modulus of elasticity (ε) than the other two sites. Plants from the cool-wet site had lower specific leaf area (SLA) and plants from the warm-dry site had lower sapwood density (WD). Overall, key hydraulic traits were generally conserved across populations despite differences in mean site water availability, and the safety-efficiency trade-off was absent in this species. These results suggest that B. serrata has limited ability to adjust hydraulic architecture in response to environmental change and thus may be susceptible to climate change-type drought stress.

Publication

Interactive direct and plant‐mediated effects of elevated atmospheric [CO₂] and temperature on a eucalypt‐feeding insect herbivore

Publisher: Wiley

Date: 11-02-2013

DOI: 10.1111/GCB.12142

Abstract: Understanding the direct and indirect effects of elevated [CO2 ] and temperature on insect herbivores and how these factors interact are essential to predict ecosystem-level responses to climate change scenarios. In three concurrent glasshouse experiments, we measured both the in idual and interactive effects of elevated [CO2 ] and temperature on foliar quality. We also assessed the interactions between their direct and plant-mediated effects on the development of an insect herbivore of eucalypts. Eucalyptus tereticornis saplings were grown at ambient or elevated [CO2 ] (400 and 650 μmol mol(-1) respectively) and ambient or elevated ( + 4 °C) temperature for 10 months. Doratifera quadriguttata (Lepidoptera: Limacodidae) larvae were feeding directly on these trees, on their excised leaves in a separate glasshouse, or on excised field-grown leaves within the temperature and [CO2 ] controlled glasshouse. To allow insect gender to be determined and to ensure that any sex-specific developmental differences could be distinguished from treatment effects, insect development time and consumption were measured from egg hatch to pupation. No direct [CO2 ] effects on insects were observed. Elevated temperature accelerated larval development, but did not affect leaf consumption. Elevated [CO2 ] and temperature independently reduced foliar quality, slowing larval development and increasing consumption. Simultaneously increasing both [CO2 ] and temperature reduced these shifts in foliar quality, and negative effects on larval performance were subsequently ameliorated. Negative nutritional effects of elevated [CO2 ] and temperature were also independently outweighed by the direct positive effect of elevated temperature on larvae. Rising [CO2 ] and temperature are thus predicted to have interactive effects on foliar quality that affect eucalypt-feeding insects. However, the ecological consequences of these interactions will depend on the magnitude of concurrent temperature rise and its direct effects on insect physiology and feeding behaviour.

Publication

Drought × CO2 interactions in trees: A test of the low-intercellular CO2 concentration (Ci) mechanism

Publisher: Wiley

Date: 03-11-2016

DOI: 10.1111/NPH.13715

Abstract: Models of tree responses to climate typically project that elevated atmospheric CO 2 concentration ( e C a ) will reduce drought impacts on forests. We tested one of the mechanisms underlying this interaction, the ‘low C i effect’, in which stomatal closure in drought conditions reduces the intercellular CO 2 concentration ( C i ), resulting in a larger relative enhancement of photosynthesis with e C a , and, consequently, a larger relative biomass response. We grew two Eucalyptus species of contrasting drought tolerance at ambient and elevated C a for 6–9 months in large pots maintained at 50% (drought) and 100% field capacity. Droughted plants did not have significantly lower C i than well‐watered plants, which we attributed to long‐term changes in leaf area. Hence, there should not have been an interaction between e C a and water availability on biomass, and we did not detect one. The xeric species did have higher C i than the mesic species, indicating lower water‐use efficiency, but both species exhibited similar responses of photosynthesis and biomass to e C a , owing to compensatory differences in the photosynthetic response to C i . Our results demonstrate that long‐term acclimation to drought, and coordination among species traits may be important for predicting plant responses to e C a under low water availability.

Publication

Impact of eastern dwarf mistletoe (Arceuthobium pusillum) infection on the needles of red spruce (Picea rubens) and white spruce (Picea glauca): oxygen exchange, morphology and composition

Publisher: Oxford University Press (OUP)

Date: 10-2006

DOI: 10.1093/TREEPHYS/26.10.1325

Abstract: Eastern dwarf mistletoe (Arceuthobium pusillum Peck) is a hemiparasitic angiosperm that infects white spruce (Picea glauca (Moench) Voss) and red spruce (P. rubens Sarg.) in northeastern North America. The effects of mistletoe infection differ substantially between white and red spruce, with white spruce suffering greater infection-induced mortality. In the present study, we sought to determine the role that species-specific differences in needle-scale responses to parasitism may play in the observed differences in the effect of infection on host tree health. Based on the measurements made, the most apparent effect of parasitism was a reduction in needle size distal to infections. The magnitude of this reduction was greater in white spruce than in red spruce. Eastern dwarf mistletoe was a sink for host photosynthate in red spruce and white spruce however, there were no adjustments in needle photosynthetic capacities in either host to accommodate the added sink demands of the parasite. Needle total nonstructural carbohydrate concentrations (TNC) were also unaltered by infection. Red spruce needles had higher TNC concentrations despite having lower overall photosynthetic capacities, suggesting that red spruce may be more sink limited and therefore better able to satisfy the added sink demands of parasitic infection. However, if carbon availability limits the growth of the mistletoe, one may expect that the extent of the parasitic infection would be greater in red spruce. Yet in the field, the extent of infection is generally greater in white spruce. Taken together, these results suggest that dwarf mistletoe may not substantially perturb the carbon balance of either host spruce species and that species-specific differences in needle-scale responses to the parasite cannot explain the contrasting effects of infection on white spruce and red spruce.

Publication

Rooting depth explains [CO 2]× drought interaction in Eucalyptus saligna

Publisher: Oxford University Press (OUP)

Date: 12-05-2011

DOI: 10.1093/TREEPHYS/TPR030

Abstract: Elevated atmospheric [CO(2)] (eC(a)) often decreases stomatal conductance, which may delay the start of drought, as well as alleviate the effect of dry soil on plant water use and carbon uptake. We studied the interaction between drought and eC(a) in a whole-tree chamber experiment with Eucalyptus saligna. Trees were grown for 18 months in their C(a) treatments before a 4-month dry-down. Trees grown in eC(a) were smaller than those grown in ambient C(a) (aC(a)) due to an early growth setback that was maintained throughout the duration of the experiment. Pre-dawn leaf water potentials were not different between C(a) treatments, but were lower in the drought treatment than the irrigated control. Counter to expectations, the drought treatment caused a larger reduction in canopy-average transpiration rates for trees in the eC(a) treatment compared with aC(a). Total tree transpiration over the dry-down was positively correlated with the decrease in soil water storage, measured in the top 1.5 m, over the drying cycle however, we could not close the water budget especially for the larger trees, suggesting soil water uptake below 1.5 m depth. Using neutron probe soil water measurements, we estimated fractional water uptake to a depth of 4.5 m and found that larger trees were able to extract more water from deep soil layers. These results highlight the interaction between rooting depth and response of tree water use to drought. The responses of tree water use to eC(a) involve interactions between tree size, root distribution and soil moisture availability that may override the expected direct effects of eC(a). It is essential that these interactions be considered when interpreting experimental results.

Publication

Variations in dark respiration and mitochondrial numbers within needles of Pinus radiata grown in ambient or elevated CO2 partial pressure

Publisher: Oxford University Press (OUP)

Date: 03-2004

DOI: 10.1093/TREEPHYS/24.3.347

Abstract: Within-leaf variations in cell size, mitochondrial numbers and dark respiration rates were compared in the most recently expanded tip, the mid-section and base of needles of Pinus radiata D. Don trees grown for 4 years in open-top chambers at ambient (36 Pa) or elevated (65 Pa) carbon dioxide partial pressure (p(CO2)a). Mitochondrial numbers and respiratory activity varied along the length of the needle, with the highest number of mitochondria per unit cytoplasm and the highest rate of respiration per unit leaf area at the base of the needle. Regardless of the location of the cells (tip, middle or basal sections), needles collected from trees grown in elevated p(CO2)a had nearly twice the number of mitochondria per unit cytoplasm as those grown in ambient p(CO2)a. This stimulation of mitochondrial density by growth at elevated p(CO2)a was greater at the tip of the needle (2.7 times more mitochondria than in needles grown in ambient CO2) than at the base of the needle (1.7 times). The mean size of in idual mitochondria was unaffected either by growth at elevated p(CO2)a or by position along the needle. Tree growth at elevated p(CO2)a had a variable effect on respiration per unit leaf area, significantly increasing respiration in the tip of the needles (+25%) and decreasing respiration at the mid-section and base of the needles (-14% and -25%, respectively). Although a simple relationship between respiration per unit leaf area and mitochondrial number per unit cytoplasm was found within each CO2 treatment, the variable effect of growth at elevated p(CO2)a on respiration along the length of the needles indicates that a more complex relationship must determine the association between structure and function in these needles.

Publication

Dry mass production, allocation patterns and water use efficiency of two conifers with different water use strategies under elevated [CO2], warming and drought conditions

Publisher: Springer Science and Business Media LLC

Date: 02-07-2018

DOI: 10.1007/S10342-018-1128-X

Publication

Seasonal acclimation of leaf respiration in Eucalyptus saligna trees: impacts of elevated atmospheric CO2 and summer drought

Publisher: Wiley

Date: 02-11-2010

DOI: 10.1111/J.1365-2486.2010.02325.X

Publication

Drought response strategies define the relative contributions of hydraulic dysfunction and carbohydrate depletion during tree mortality

Publisher: Wiley

Date: 10-12-2013

DOI: 10.1111/NPH.12064

Abstract: Plant survival during drought requires adequate hydration in living tissues and carbohydrate reserves for maintenance and recovery. We hypothesized that tree growth and hydraulic strategy determines the intensity and duration of the ‘physiological drought’, thereby affecting the relative contributions of loss of hydraulic function and carbohydrate depletion during mortality. We compared patterns in growth rate, water relations, gas exchange and carbohydrate dynamics in three tree species subjected to prolonged drought. Two E ucalyptus species ( E . globulus , E . smithii ) exhibited high growth rates and water‐use resulting in rapid declines in water status and hydraulic conductance. In contrast, conservative growth and water relations in P inus radiata resulted in longer periods of negative carbon balance and significant depletion of stored carbohydrates in all organs. The ongoing demand for carbohydrates from sustained respiration highlighted the role that duration of drought plays in facilitating carbohydrate consumption. Two drought strategies were revealed, differentiated by plant regulation of water status: plants maximized gas exchange, but were exposed to low water potentials and rapid hydraulic dysfunction and tight regulation of gas exchange at the cost of carbohydrate depletion. These findings provide evidence for a relationship between hydraulic regulation of water status and carbohydrate depletion during terminal drought.

Publication

Flooding and prolonged drought have differential legacy impacts on soil nitrogen cycling, microbial communities and plant productivity

Publisher: Springer Science and Business Media LLC

Date: 11-08-2018

DOI: 10.1007/S11104-018-3774-7

Publication

Genomic constraints to drought adaptation

Publisher: Cold Spring Harbor Laboratory

Date: 08-08-2021

DOI: 10.1101/2021.08.07.455511

Abstract: Global shifts in climate and precipitation patterns are altering the ersity and structure of forests. The ability for species to adapt is especially difficult for long lived foundation species with unknown genetic and trait ersity. We harnessed genomic, physiological, and climate data to determine adaptation constraints. We used denovo assembly and 6.5 million genomic variants with drought related traits from 432 in iduals sourced from across the complete range of the foundation tree species Corymbia calophylla . We found genomic variants determining traits predominantly in gene regulatory regions. The ability for populations to adapt was limited by within population genetic ersity associated with traits, and epistatic interactions within traits and pleiotropic interactions among traits. Nevertheless, we could accurately predict adaptive traits using genomic and climate data to guide reforestation. Our study indicated that some populations may contain variation sufficient for the species to adapt to the effects of drought, while other populations will need increased variability from those sources.

Publication

Feature: Improving our knowledge of drought‐induced forest mortality through experiments, observations, and modeling

Publisher: Wiley

Date: 18-09-2013

DOI: 10.1111/NPH.12502

Publication

Photosynthesis and reflectance indices for rainforest species in ecosystems undergoing progression and retrogression along a soil fertility chronosequence in New Zealand

Publisher: Springer Science and Business Media LLC

Date: 15-04-2005

DOI: 10.1007/S00442-005-0068-6

Abstract: Measurements of photosynthesis at saturating irradiance and CO2 partial pressure, Amax, "adjusted" normalised difference vegetation index, RaNDVI, and photochemical reflectance index, RPRI, were made on trees s led along a soil chronosequence to investigate the relationship between carbon uptake and ecosystem development in relation to nutrient availability. Measurements were made on the three most dominant species at six sites along the sequence in South Westland, New Zealand with soil age ranging from < 6 to 120,000 years resulting from the retreat of the Franz Josef glacier. The decrease in soil phosphorus availability with increasing soil age and high soil nitrogen availability at the two youngest sites, due to the presence of a nitrogen-fixing species, provided marked differences in nutrient availability. Mean Amax was high at the two youngest sites, then decreased markedly with increasing site age. Analysis of the data for in idual species within sites revealed separation of groups of species in the response of Amax to Nm and Pm, suggesting complex interactions between the two nutrients. There were strong linear relationships for leaf-level RaNDVI and RPRI with Amax, at high irradiance, showing that measurements of reflectance indices can be used to estimate Amax for foliage with a range in morphology and nutrient concentrations. Notwithstanding the change in species composition from angiosperms to conifers with increasing site age, the presence of nitrogen-fixing species, the variability in foliage morphology from flat leaves to imbricate scales and a wide range in foliar nitrogen and phosphorus concentrations, there were strong positive linear relationships between site average Amax and foliage nitrogen, Nm, and phosphorus, Pm, concentrations on a foliage mass basis. The results provide insights to interpret the regulation of photosynthesis across natural ecosystems with marked gradients in nitrogen and phosphorus availability.

Publication

Warming drives sustained plant phosphorus demand in a humid tropical forest.

Publisher: Wiley

Date: 20-04-2022

DOI: 10.1111/GCB.16194

Abstract: Phosphorus (P) is often one of the most limiting nutrients in highly weathered soils of humid tropical forests and may regulate the responses of carbon (C) feedback to climate warming. However, the response of P to warming at the ecosystem level in tropical forests is not well understood because previous studies have not comprehensively assessed changes in multiple P processes associated with warming. Here, we detected changes in the ecosystem P cycle in response to a 7-year continuous warming experiment by translocating model plant-soil ecosystems across a 600-m elevation gradient, equivalent to a temperature change of 2.1°C. We found that warming increased plant P content (55.4%) and decreased foliar N:P. Increased plant P content was supplied by multiple processes, including enhanced plant P resorption (9.7%), soil P mineralization (15.5% decrease in moderately available organic P), and dissolution (6.8% decrease in iron-bound inorganic P), without changing litter P mineralization and leachate P. These findings suggest that warming sustained plant P demand by increasing the biological and geochemical controls of the plant-soil P-cycle, which has important implications for C fixation in P-deficient and highly productive tropical forests in future warmer climates.

Publication

Leaf respiration at different canopy positions in sweetgum (Liquidambar styraciflua) grown in ambient and elevated concentrations of carbon dioxide in the field

Publisher: Oxford University Press (OUP)

Date: 11-2002

DOI: 10.1093/TREEPHYS/22.15-16.1157

Abstract: Trees exposed to elevated CO2 partial pressure ([CO2]) generally show increased rates of photosynthesis and growth, but effects on leaf respiration are more variable. The causes of this variable response are unresolved. We grew 12-year-old sweetgum trees (Liquidambar styraciflua L.) in a Free-Air CO2 Enrichment (FACE) facility in ambient [CO2] (37/44 Pa daytime/nighttime) and elevated [CO2] (57/65 Pa daytime/nighttime) in native soil at Oak Ridge National Environmental Research Park. Nighttime respiration (R(N)) was measured on leaves in the upper and lower canopy in the second (1999) and third (2000) growing seasons of CO2 fumigation. Leaf respiration in the light (R(L)) was estimated by the technique of Brooks and Farquhar (1985) in the upper canopy during the third growing season. There were no significant short-term effects of elevated [CO2] on R(N) or long-term effects on R(N) or R(L), when expressed on an area, mass or nitrogen (N) basis. Upper-canopy leaves had 54% higher R(N) (area basis) than lower-canopy leaves, but this relationship was unaffected by CO2 growth treatment. In August 2000, R(L) was about 40% of R(N) in the upper canopy. Elevated [CO(2)] significantly increased the number of leaf mitochondria (62%), leaf mass per unit area (LMA 9%), and leaf starch (31%) compared with leaves in ambient [CO(2)]. Upper-canopy leaves had a significantly higher number of mitochondria (73%), N (53%), LMA (38%), sugar (117%) and starch (23%) than lower-canopy leaves. Growth in elevated [CO2] did not affect the relationships (i.e., intercept and slope) between R(N) and the measured leaf characteristics. Although no factor explained more than 45% of the variation in R(N), leaf N and LMA were the best predictors for R(N). Therefore, the response of RN to CO2 treatment and canopy position was largely dependent on the magnitude of the effect of elevated [CO2] or canopy position on these characteristics. Because elevated [CO2] had little or no effect on N or LMA, there was no effect on R(N). Canopy position had large effects on these leaf characteristics, however, such that upper-canopy leaves exhibited higher R(N) than lower-canopy leaves. We conclude that elevated [CO2] does not directly impact leaf respiration in sweetgum and that barring changes in leaf nitrogen or leaf chemical composition, long-term effects of elevated [CO2] on respiration in this species will be minimal.

Publication

The decoupling between gas exchange and water potential of Cinnamomum camphora seedlings during drought recovery and its relation to ABA accumulation in leaves

Publisher: Oxford University Press (OUP)

Date: 26-08-2020

DOI: 10.1093/JPE/RTAA056

Abstract: Drought stress and the degree of drought severity are predicted to rise under highly variable patterns of precipitation due to climate change, while the capacity of trees to cope with drought recovery through physiological and biochemical adjustment remains unclear. We aimed to examine the coupling of physiology and biochemistry in trees during drought and the following recovery. Potted seedlings of Cinnamomum c hora were grown under well watered conditions prior to the experimental drought stress, which was initiated by withholding water. Seedlings were rewatered following attainment of two drought severities: mild drought (stomatal closure) and moderate drought (ψxylem = −1.5 MPa). We measured leaf-level water potential, gas exchange (photosynthesis and stomatal conductance), abscisic acid (ABA), proline and non-structural carbohydrates (NSCs) concentrations in seedlings of C. c hora during drought and a 4-day recovery. We found that drought severity largely determined physiological and biochemical responses and affected the rate of recovery. Stomatal closure occurred at the mild drought stress, accompanied with ABA accumulation in leaves and decline in water potential, while leaf proline accumulation and variable NSC were evident at the moderate drought stress. More severe drought stress led to delayed recovery of gas exchange, but it did not have significant effect on water potential recovery. The relationships of water potential and gas exchange differed during drought stress and post-drought recovery. There was tight coupling between water potential and gas exchange during drought, but not during rewatering due to high ABA accumulation in leaves, thereby delaying recovery of stomatal conductance. Our results demonstrate that ABA could be an important factor in delaying the recovery of stomatal conductance following rewatering and after water potential recovery of C. c hora. Furthermore, greater drought severity had significant impacts on the rate of recovery of tree physiology and biochemistry.

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David Tissue

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