Marilyn Ball

Light-dependent maintenance of hydraulic function in mangrove branches: do xylary chloroplasts play a role in embolism repair?

Publisher: Wiley

Date: 17-05-2012

DOI: 10.1111/J.1469-8137.2012.04187.X

Abstract: • To clarify the role of branch photosynthesis in tree functioning, the presence and function of chloroplasts in branch xylem tissue were studied in a erse range of mangrove species growing in Australia. • The presence of xylary chloroplasts was observed via chlorophyll fluorescence of transverse sections. Paired, attached branches were selected to study the effects of covering branches with aluminium foil on the gas exchange characteristics of leaves and the hydraulic conductivity of branches. • Xylary chloroplasts occurred in all species, but were differently distributed among living cell types in the xylem. Covering stems altered the gas exchange characteristics of leaves, such that water-use efficiency was greater in exposed leaves of covered than of uncovered branches. • Leaf-specific hydraulic conductivity of stems was lower in covered than in uncovered branches, implicating stem photosynthesis in the maintenance of hydraulic function. Given their proximity to xylem vessels, we suggest that xylary chloroplasts may play a role in light-dependent repair of embolized xylem vessels.

Cover Image

Publisher: Wiley

Date: 10-08-2022

DOI: 10.1111/PCE.14418

Primary nerve (vein) density influences spatial heterogeneity of photosynthetic response to drought in two Acacia species

Publisher: CSIRO Publishing

Date: 2010

DOI: 10.1071/FP10062

Abstract: We examined the relationship between variation in phyllode nerve density and the spatio-temporal response of the photosynthetic apparatus to water-stress in two Acacia s.str. species with contrasting nerve patterns: Acacia floribunda (Vent.) Willd and Acacia pycnantha Benth. A. floribunda had greater primary nerve density than A. pycnantha and also showed greater spatial homogeneity in photosynthetic function with drought than phyllodes of A. pycnantha. A. pycnantha had lower maximum quantum efficiency of PSII in phyllode tissue further from primary nerves consistent with its lower primary nerve density. Further, A. floribunda phyllodes maintained function of the photosynthetic apparatus with drought for longer and recovered more swiftly from drought than A. pycnantha. These findings suggest that greater primary nerve density may enhance drought tolerance and are consistent with the observed predominance of acacias with high primary nerve density in areas with lower precipitation.

Revisiting yield in terms of phloem transport to grains suggests phloem sap movement might be homeostatic in wheat

Publisher: Authorea, Inc.

Date: 10-04-2023

DOI: 10.22541/AU.168111012.22494064/V1

Abstract: Phloem sap transport, velocity and allocation have been proposed to play a role in physiological limitations of crop yield, along with photosynthetic activity or water use efficiency. Although there is clear evidence that carbon allocation to grains effectively drives yield in cereals like wheat (as reflected by the harvest index), the influence of phloem transport rate and velocity is less clear. Here, we took advantage of previously published data on yield, respiration, carbon isotope composition, nitrogen content and water consumption in winter wheat cultivars grown across several sites with or without irrigation, to express grain production in terms of phloem sucrose transport and compare with xylem water transport. Our results suggest that phloem sucrose transport rate follows the same relationship with phloem N transport regardless of irrigation conditions and cultivars, and seems to depend mostly on grain weight (i.e. mg per grain). When compared to xylem sap water movement, phloem sap velocity (in m s ) was 5.8 to 7.7 times lower. Depending on the assumption made for phloem sap sucrose concentration, either phloem sap velocity or its proportionality coefficient to xylem velocity change little with environmental conditions. Taken as a whole, phloem transport from leaves to grains seems to be homeostatic within a narrow range of values and following relationships with other plant physiological parameters across cultivars and conditions. This suggests that phloem transport per se is not a limitation for yield in wheat but rather, is controlled to sustain grain filling.

Diurnal and seasonal variation in light and dark respiration in field-grown Eucalyptus pauciflora

Publisher: Oxford University Press (OUP)

Date: 08-2015

DOI: 10.1093/TREEPHYS/TPV065

Abstract: Respiration from vegetation is a substantial part of the global carbon cycle and the responses of plant respiration to daily and seasonal fluctuations in temperature and light must be incorporated in models of terrestrial respiration to accurately predict these CO2 fluxes. We investigated how leaf respiration (R) responded to changes in leaf temperature (T(leaf)) and irradiance in field-grown saplings of an evergreen tree (Eucalyptus pauciflora Sieb. ex Spreng). Seasonal shifts in the thermal sensitivity of leaf R in the dark (R(dark)) and in the light (R(light)) were assessed by allowing T(leaf) to vary over the day in field-grown leaves over a year. The Q10 of R (i.e., the relative increase in R for a 10 °C increase in T(leaf)) was similar for R(light) and R(dark) and had a value of ∼ 2.5 there was little seasonal change in the Q10 of either R(light) or R(dark), indicating that we may be able to use similar functions to model short-term temperature responses of R in the dark and in the light. Overall, rates of R(light) were lower than those of R(dark), and the ratio of R(light)/R(dark) tended to increase with rising T(leaf), such that light suppression of R was reduced at high T(leaf) values, in contrast to earlier work with this species. Our results suggest we cannot assume that R(light)/R(dark) decreases with increasing T(leaf) on daily timescales, and highlights the need for a better mechanistic understanding of what regulates light suppression of R in leaves.

Does soil nitrogen influence growth, water transport and survival of snow gum (Eucalyptus pauciflora Sieber ex Sprengel.) under CO2 enrichment?

Publisher: Wiley

Date: 05-2009

DOI: 10.1111/J.1365-3040.2009.01949.X

Abstract: Eucalyptus pauciflora Sieber ex Sprengel. (snow gum) was grown under ambient (370 microL L(-1)) and elevated (700 microL L(-1)) atmospheric [CO2] in open-top chambers (OTCs) in the field and temperature-controlled glasshouses. Nitrogen applications to the soil ranged from 0.1 to 2.75 g N per plant. Trees in the field at high N levels grew rapidly during summer, particularly in CO2-enriched atmosphere, but suffered high mortality during summer heatwaves. Generally, wider and more numerous secondary xylem vessels at the root-shoot junction in CO2-enriched trees conferred fourfold higher below-ground hydraulic conductance. Enhanced hydraulic capacity was typical of plants at elevated [CO2] (in which root and shoot growth was accelerated), but did not result from high N supply. However, because high rates of N application consistently made trees prone to dehydration during heatwaves, glasshouse studies were required to identify the effect of N nutrition on root development and hydraulics. While the effects of elevated [CO2] were again predominantly on hydraulic conductivity, N nutrition acted specifically by constraining deep root penetration into soil. Specifically, 15-40% shallower root systems supported marginally larger shoot canopies. Independent changes to hydraulics and root penetration have implications for survival of fertilized trees under elevated atmospheric [CO2], particularly during water stress.

Space and time dependence of temperature and freezing in evergreen leaves

Publisher: CSIRO Publishing

Date: 2002

DOI: 10.1071/FP02037

Abstract: Infrared video thermography was used to study space and time dependence of freezing in intact, attached leaves of snow gum (Eucalyptus pauciflora Sieb. ex Spreng.) seedlings. Freezing initiated in the midvein and spread through the apoplast at 10 mm s–1. Freezing of apoplastic water was detected by a local, rapid increase in temperature, and was followed by a slower increase in leaf temperature to the equilibrium freezing temperature as symplastic water moved from cells to extracellular sites of ice formation. The duration of freezing varied with position, leaf thickness and water content. Most of the cellular water in the leaf tip and margins froze quickly, while freezing was slower near the petiole and midvein. Regions that had frozen more rapidly then began to cool more rapidly, producing steep gradients in leaf temperatures and hence also freeze-induced dehydration. Thus, spatial variation in physical properties of leaves could affect the distribution of minimum leaf temperatures, and hence, the distribution and extent of damage due to freeze-induced dehydration. These results are consistent with patterns of freezing damage in autumn when the duration of freezing may be insufficient for the whole leaf to freeze before sunrise, and may explain the general observation of increased leaf water content and thickness with altitude.

The effect of nutrient enrichment on growth, photosynthesis and hydraulic conductance of dwarf mangroves in Panamá

Publisher: Wiley

Date: 02-2004

DOI: 10.1046/J.0269-8463.2004.00805.X

Pit membrane porosity and water stress-induced cavitation in four co-existing dry rainforest tree species

Publisher: Oxford University Press (OUP)

Date: 2003

DOI: 10.1104/PP.014100

Abstract: Aspects of xylem anatomy and vulnerability to water stress-induced embolism were examined in stems of two drought-deciduous species, Brachychiton australis (Schott and Endl.) A. Terracc. and Cochlospermum gillivraei Benth., and two evergreen species, Alphitonia excelsa (Fenzal) Benth. and Austromyrtus bidwillii (Benth.) Burret., growing in a seasonally dry rainforest. The deciduous species were more vulnerable to water stress-induced xylem embolism. B. australis andC. gillivraei reached a 50% loss of hydraulic conductivity at −3.17 MPa and −1.44 MPa, respectively a 50% loss of hydraulic conductivity occurred at −5.56 MPa in A. excelsa and −5.12 MPa in A. bidwillii. To determine whether pit membrane porosity was responsible for greater vulnerability to embolism (air seeding hypothesis), pit membrane structure was examined. Expected pore sizes were calculated from vulnerability curves however, the predicted inter-specific variation in pore sizes was not detected using scanning electron microscopy (pores were not visible to a resolution of 20 nm). Suspensions of colloidal gold particles were then perfused through branch sections. These experiments indicated that pit membrane pores were between 5 and 20 nm in diameter in all four species. The results may be explained by three possibilities: (a) the pores of the expected size range were not present, (b) larger pores, within the size range to cause air seeding, were present but were rare enough to avoid detection, or (c) pore sizes in the expected range only develop while the membrane is under mechanical stress (during air seeding) due to stretching/flexing.

Higher daytime leaf temperatures contribute to lower freeze tolerance under elevated CO2

Publisher: Wiley

Date: 06-2006

DOI: 10.1111/J.1365-3040.2005.01482.X

Abstract: Elevated atmospheric CO2 adversely affects freezing tolerance in many evergreens, but the underlying mechanism(s) have been elusive. We compared effects of elevated CO2 with those of daytime warming on acclimation of snow gum (Eucalyptus pauciflora) to freezing temperatures under field conditions. Reduction in stomatal conductance g(c) under elevated CO2 was shown to cause leaf temperature to increase by up to 3 degrees C. In this study, this increase in leaf temperature was simulated under ambient CO2 conditions by using a free air temperature increase (FATI) system to warm snow gum leaves during daytime, thereby increasing the diurnal range in temperature without affecting temperature minima. Acclimation to freezing temperatures was assessed using measures of electrolyte leakage and photosynthetic efficiency of leaf discs exposed to different nadir temperatures. Here, we show that both elevated CO2 and daytime warming delayed acclimation to freezing temperatures for 2-3 weeks after which time freeze tolerance of the treated plants in both the FATI and open top chamber (OTC) experiments did not differ from control plants. Our results support the hypothesis that delayed development of freezing tolerance under elevated CO2 is because of higher daytime leaf temperatures under elevated CO2. Thus, potential gains in productivity in response to increasing atmospheric CO2 and prolonging the growing season may be reduced by an increase in freezing stress in frost-prone area.

A mutation that eliminates bundle sheath extensions reduces leaf hydraulic conductance, stomatal conductance and assimilation rates in tomato (Solanum lycopersicum)

Publisher: Wiley

Date: 30-09-2015

DOI: 10.1111/NPH.13084

Abstract: Bundle sheath extensions ( BSE s) are key features of leaf structure whose distribution differs among species and ecosystems. The genetic control of BSE development is unknown, so BSE physiological function has not yet been studied through mutant analysis. We screened a population of ethyl methanesulfonate ( EMS )‐induced mutants in the genetic background of the tomato ( S olanum lycopersicum ) model M icro‐ T om and found a mutant lacking BSE s. The leaf phenotype of the mutant strongly resembled the tomato mutant obscuravenosa ( obv ). We confirmed that obv lacks BSE s and that it is not allelic to our induced mutant, which we named obv‐2 . Leaves lacking BSE s had lower leaf hydraulic conductance and operated with lower stomatal conductance and correspondingly lower assimilation rates than wild‐type leaves. This lower level of function occurred despite similarities in vein density, midvein vessel diameter and number, stomatal density, and leaf area between wild‐type and mutant leaves, the implication being that the lack of BSE s hindered water dispersal within mutant leaves. Our results comparing near‐isogenic lines within a single species confirm the hypothesised role of BSE s in leaf hydraulic function. They further pave the way for a genetic model‐based analysis of a common leaf structure with deep ecological consequences.

Leaf respiration of snow gum in the light and dark. Interactions between temperature and irradiance

Publisher: Oxford University Press (OUP)

Date: 03-2000

DOI: 10.1104/PP.122.3.915

Abstract: We investigated the effect of temperature and irradiance on leaf respiration (R, non-photorespiratory mitochondrial CO(2) release) of snow gum (Eucalyptus pauciflora Sieb. ex Spreng). Seedlings were hydroponically grown under constant 20 degrees C, controlled-environment conditions. Measurements of R (using the Laisk method) and photosynthesis (at 37 Pa CO(2)) were made at several irradiances (0-2,000 micromol photons m(-2) s(-1)) and temperatures (6 degrees C-30 degrees C). At 15 degrees C to 30 degrees C, substantial inhibition of R occurred at 12 micromol photons m(-2) s(-1), with maximum inhibition occurring at 100 to 200 micromol photons m(-2) s(-1). Higher irradiance had little additional effect on R at these moderate temperatures. The irradiance necessary to maximally inhibit R at 6 degrees C to 10 degrees C was lower than that at 15 degrees C to 30 degrees C. Moreover, although R was inhibited by low irradiance at 6 degrees C to 10 degrees C, it recovered with progressive increases in irradiance. The temperature sensitivity of R was greater in darkness than under bright light. At 30 degrees C and high irradiance, light-inhibited rates of R represented 2% of gross CO(2) uptake (v(c)), whereas photorespiratory CO(2) release was approximately 20% of v(c). If light had not inhibited leaf respiration at 30 degrees C and high irradiance, R would have represented 11% of v(c). Variations in light inhibition of R can therefore have a substantial impact on the proportion of photosynthesis that is respired. We conclude that the rate of R in the light is highly variable, being dependent on irradiance and temperature.

Intense storms and the delivery of materials that relieve nutrient limitations in mangroves of an arid zone estuary

Publisher: CSIRO Publishing

Date: 2020

DOI: 10.1071/FP11027

Abstract: Tropical cyclones can be devastating to ecosystems, but they can also result in pulses of fresh water and sediments delivered in floodwaters to the coastal zone. In the arid zone the pulses provided by cyclones may be particularly important for the maintenance of productivity. We examined the impacts of Cyclone Pancho on growth and nutrient limitations to growth in mangroves on the arid coast of Western Australia. We found that growth of trees was enhanced after the cyclone, more than doubling their rates of stem extension. Fertilisation studies showed that before the cyclone tree growth was nutrient limited. After the cyclone fertilisation treatments had no significant effect on growth, indicating nutrients had been delivered during the storm. Additionally, before the cyclone the efficiency of resorption of phosphorus and nitrogen from senescent leaves was higher than after the cyclone, suggesting that nutrient availability was enhanced. Analysis of stable isotopes of leaf tissue indicated that the cyclone was associated with small changes in water use efficiency, consistent with decreased soil salinity associated with the cyclone. There was, however, significant reductions in δ15N indicating enhanced N supply potentially from a new source. We conclude that in the arid zone, floodwater associated with cyclones is important for the delivery of nutrient subsidies that stimulate mangrove growth and that predicted future reductions in the frequency of cyclones will have negative impacts on the productivity of these ecosystems.

Differences in plant function in phosphorus- and nitrogen-limited mangrove ecosystems

Publisher: Wiley

Date: 08-2006

DOI: 10.1111/J.1469-8137.2006.01851.X

Abstract: Mangrove ecosystems can be either nitrogen (N) or phosphorus (P) limited and are therefore vulnerable to nutrient pollution. Nutrient enrichment with either N or P may have differing effects on ecosystems because of underlying differences in plant physiological responses to these nutrients in either N- or P-limited settings. Using a common mangrove species, Avicennia germinans, in sites where growth was either N or P limited, we investigated differing physiological responses to N and P limitation and fertilization. We tested the hypothesis that water uptake and transport, and hydraulic architecture, were the main processes limiting productivity at the P-limited site, but that this was not the case at the N-limited site. We found that plants at the P-deficient site had lower leaf water potential, stomatal conductance and photosynthetic carbon-assimilation rates, and less conductive xylem, than those at the N-limited site. These differences were greatly reduced with P fertilization at the P-limited site. By contrast, fertilization with N at the N-limited site had little effect on either photosynthetic or hydraulic traits. We conclude that growth in N- and P-limited sites differentially affect the hydraulic pathways of mangroves. Plants experiencing P limitation appear to be water deficient and undergo more pronounced changes in structure and function with relief of nutrient deficiency than those in N-limited ecosystems.

Salinity tolerance in the mangroves Aegiceras corniculatum and Avicennia marina. I. Water use in relation to growth, carbon partitioning, and salt balance

Publisher: CSIRO Publishing

Date: 1988

DOI: 10.1071/PP9880447

Abstract: The water use characteristics of two mangrove species, Aegiceras corniculatum and Avicennia marina, in salinities of 50, 250 and 500 mol m-3 NaCI and leaf-to-air vapour pressure differences of 6, 12 and 24 mbar were studied in relation to growth, carbon partitioning and salt balance. The net water use efficiency in A. corniculatum declined with increasing salinity and decreasing humidity. In contrast, water use was more conservative in A. marina, which maintained the net water use efficiency almost constant with variation in salinity. Aegiceras corniculatum maintained higher rates of water uptake and higher leaf area lant mass ratios than A. marina. Growth of both species declined with increasing salinity, with A. corniculatum being the more sensitive species. Differences in growth rates between species and between treatments were consistent with differences in the assimilation rate and leaf areal plant mass ratio. Salt exclusion by both species increased from 90 to 97% with increase in salinity from 50 to 500 mol m-3 NaCl. The xylem Cl- concentrations increased with increase in salinity, but decreased with increase in shoot evaporation rates such that the salt flux to the leaves did not increase with increase in evaporation rates at a given salinity. Despite similarities in the salt fluxes to leaves, the transport of Cl- to the shoot per unit of shoot growth increased more with increasing salinity in A. corniculatum than in A. marina because the net water use efficiencies were lower in the former species. Thus, the amount of salt secreted per mole water transpired (and hence also per mole carbon gained) increased more with increasing salinity in A. corniculatum than in A. marina. These differences in salt balance may be associated with the greater sensitivity of A. corniculaturn to increasing salinity. The possible ecological significance of these findings is discussed.

Temperature responses of photosynthesis and respiration in a sub-Antarctic megaherb from Heard Island

Publisher: CSIRO Publishing

Date: 2015

DOI: 10.1071/FP14134

Abstract: Understanding the response of sub-Antarctic plants to a warming climate requires an understanding of the relationship of carbon gain and loss to temperature. In a field study on Heard Island, we investigated the responses of photosynthesis and respiration of the sub-Antarctic megaherb Pringlea antiscorbutica R. Br. to temperature. This was done by instantaneously manipulating leaf temperature in a gas exchange cuvette on plants adapted to natural temperature variation along an altitudinal gradient. There was little altitudinal variation in the temperature response of photosynthesis. Photosynthesis was much less responsive to temperature than electron transport, suggesting that Rubisco activity was generally the rate-limiting process. The temperature response of leaf respiration rates was greater in cold-grown (high altitude) plants compared with warm-grown (low altitude) plants. This thermal acclimation would enable plants to maintain a positive carbon budget over a greater temperature range.

Water redistribution determines photosynthetic responses to warming and drying in two polar mosses

Publisher: CSIRO Publishing

Date: 2014

DOI: 10.1071/FP13160

Abstract: Predicting impacts of climate change requires an understanding of the sensitivity of species to temperature, including conflated changes in humidity. Physiological responses to temperature and clump-to-air vapour pressure difference (VPD) were compared in two Antarctic moss species, Ceratodon purpureus (Hedw.) Brid. and Schistidium antarctici (Cardot) L.I. Savicz & Smirnova. Temperatures from 8 to 24°C had no significant effects on photosynthesis or recovery from drying, whereas high VPD accelerated drying. In Schistidium, which lacks internal conduction structures, shoots dried more slowly than the clump, and photosynthesis ceased at high shoot relative water content (RWC), behaviour consistent with a strategy of drought avoidance although desiccation tolerant. In contrast, shoots of Ceratodon have a central vascular core, but dried more rapidly than the clump. These results imply that cavitation of the hydroid strand enables hydraulic isolation of extremities during rapid drying, effectively slowing water loss from the clump. Ceratodon maintained photosynthetic activity during drying to lower shoot RWC than Schistidium, consistent with a strategy of drought tolerance. These ecophysiological characteristics may provide a functional explanation for the differential distribution of Schistidium and Ceratodon along moisture gradients in Antarctica. Thus, predicting responses of non-vascular vegetation to climate change at high latitudes requires greater focus on VPD and hydraulics than temperature.

The utilization of lightflecks for growth in four Australian rain‐forest species

Publisher: Wiley

Date: 04-1997

DOI: 10.1046/J.1365-2435.1997.00073.X

Foliar water uptake via cork warts in mangroves of the Sonneratia genus.

Publisher: Wiley

Date: 08-07-2021

DOI: 10.1111/PCE.14129

Abstract: Foliar water uptake (FWU) occurs in plants of erse ecosystems however, the ersity of pathways and their associated FWU kinetics remain poorly resolved. We characterized a novel FWU pathway in two mangrove species of the Sonneratia genus, S. alba and S. caseolaris. Further, we assessed the influence of leaf wetting duration, wet-dry seasonality and leaf dehydration on leaf conductance to surface water (K

Revisiting yield in terms of phloem transport to grains suggests phloem sap movement might be homeostatic

Publisher: Wiley

Date: 11-06-2023

DOI: 10.1111/PCE.14646

Abstract: Phloem sap transport, velocity and allocation have been proposed to play a role in physiological limitations of crop yield, along with photosynthetic activity or water use efficiency. Although there is clear evidence that carbon allocation to grains effectively drives yield in cereals like wheat (as reflected by the harvest index), the influence of phloem transport rate and velocity is less clear. Here, we took advantage of previously published data on yield, respiration, carbon isotope composition, nitrogen content and water consumption in winter wheat cultivars grown across several sites with or without irrigation, to express grain production in terms of phloem sucrose transport and compare with xylem water transport. Our results suggest that phloem sucrose transport rate follows the same relationship with phloem N transport regardless of irrigation conditions and cultivars, and seems to depend mostly on grain weight (i.e., mg per grain). Depending on the assumption made for phloem sap sucrose concentration, either phloem sap velocity or its proportionality coefficient to xylem velocity change little with environmental conditions. Taken as a whole, phloem transport from leaves to grains seems to be homeostatic within a narrow range of values and following relationships with other plant physiological parameters across cultivars and conditions. This suggests that phloem transport per se is not a limitation for yield in wheat but rather, is controlled to sustain grain filling.

The apparent temperature response of leaf respiration depends on the timescale of measurements: a study of two cold climate species

Publisher: Wiley

Date: 27-02-2008

DOI: 10.1111/J.1438-8677.2008.00031.X

Abstract: Productivity and climate models often use a constant Q10 for plant respiration, assuming tight control of respiration by temperature. We studied the temperature response of leaf respiration of two cold climate species (the Australian tree Eucalyptus pauciflora and the subantarctic megaherb Pringlea antiscorbutica, both measured in a field setting) on a short timescale (minutes) during different times within a diel course, and on a longer timescale, using diel variations in ambient temperature. There were great variations in Q10 depending on measuring day, measuring time and measuring method. When Q10 was calculated from short-term (15 min) manipulations of leaf temperature, the resulting values were usually markedly smaller than when Q10 was calculated from measurements at ambient leaf temperatures spread over a day. While for E. pauciflora, Q10 estimates decreased with rising temperature (corroborating the concept of a temperature-dependent Q10), the opposite was the case for P. antiscorbutica. Clearly, factors other than temperature co-regulate both leaf respiration rates and temperature sensitivity and contribute to diel and seasonal variation of respiration.

Protection and storage of chlorophyll in overwintering evergreens

Publisher: Proceedings of the National Academy of Sciences

Date: 05-09-2000

DOI: 10.1073/PNAS.150237697

Abstract: How evergreen species store and protect chlorophyll during exposure to high light in winter remains unexplained. This study reveals that the evergreen snow gum ( Eucalyptus pauciflora Sieb. ex Spreng.) stores and protects its chlorophylls by forming special complexes that are unique to the winter-acclimated state. Our in vivo spectral and kinetic characterizations reveal a prominent component of the chlorophyll fluorescence spectrum around 715 nm at 77 K. This band coincides structurally with a loss of chlorophyll and an increase in energy-dissipating carotenoids. Functionally, the band coincides with an increased capacity to dissipate excess light energy, absorbed by the chlorophylls, as heat without intrathylakoid acidification. The increased heat dissipation helps protect the chlorophylls from photo-oxidative bleaching and thereby facilitates rapid recovery of photosynthesis in spring.

The role of freezing in setting the latitudinal limits of mangrove forests

Publisher: Wiley

Date: 29-11-2007

DOI: 10.1111/J.1469-8137.2006.01938.X

Abstract: Mangrove trees dominate coastal vegetation in tropical regions, but are completely replaced by herbaceous salt marshes at latitudes above 32 degrees N and 40 degrees S. Because water deficit can increase damage caused by freezing, we hypothesized that mangroves, which experience large deficits as a result of saline substrates, would suffer freeze-induced xylem failure. Vulnerability to freeze-induced xylem embolism was examined in the most poleward mangrove species in North America, in an area where freezing is rare but severe, and in Australia, in an area where freezing is frequent but mild. Percentage loss in hydraulic conductivity was measured following manipulations of xylem tension xylem sap ion concentration was determined using X-ray microanalysis. Species with wider vessels suffered 60-100% loss of hydraulic conductivity after freezing and thawing under tension, while species with narrower vessels lost as little as 13-40% of conductivity. These results indicate that freeze-induced embolism may play a role in setting the latitudinal limits of distribution in mangroves, either through massive embolism following freezing, or through constraints on water transport as a result of vessel size.

Xylem traits mediate a trade-off between resistance to freeze-thaw-induced embolism and photosynthetic capacity in overwintering evergreens

Publisher: Wiley

Date: 31-05-2011

DOI: 10.1111/J.1469-8137.2011.03772.X

Abstract: Hydraulic traits were studied in temperate, woody evergreens in a high-elevation heath community to test for trade-offs between the delivery of water to canopies at rates sufficient to sustain photosynthesis and protection against disruption to vascular transport caused by freeze-thaw-induced embolism. Freeze-thaw-induced loss in hydraulic conductivity was studied in relation to xylem anatomy, leaf- and sapwood-specific hydraulic conductivity and gas exchange characteristics of leaves. We found evidence that a trade-off between xylem transport capacity and safety from freeze-thaw-induced embolism affects photosynthetic activity in overwintering evergreens. The mean hydraulically weighted xylem vessel diameter and sapwood-specific conductivity correlated with susceptibility to freeze-thaw-induced embolism. There was also a strong correlation of hydraulic supply and demand across species interspecific differences in stomatal conductance and CO(2) assimilation rates were correlated linearly with sapwood- and leaf-specific hydraulic conductivity. Xylem vessel anatomy mediated an apparent trade-off between resistance to freeze-thaw-induced embolism and hydraulic and photosynthetic capacity during the winter. These results point to a new role for xylem functional traits in determining the degree to which species can maintain photosynthetic carbon gain despite freezing events and cold winter temperatures.

Frost in a future climate: modelling interactive effects of warmer temperatures and rising atmospheric [CO2] on the incidence and severity of frost damage in a temperate evergreen (Eucalyptus pauciflora)

Publisher: Wiley

Date: 27-11-2008

DOI: 10.1111/J.1365-2486.2007.01499.X

Hydraulic conductance of Acacia phyllodes (foliage) is driven by primary nerve (vein) conductance and density

Publisher: Wiley

Date: 18-10-2012

DOI: 10.1111/J.1365-3040.2011.02425.X

Abstract: We determined effects of venation traits on hydraulic conductance of phyllodes (foliage), using an array of Acacia s.str. species with erse phyllode morphologies as the source of variation. Measurements were made on phyllodes from 44 species, grown in common gardens but originating from different positions along a precipitation gradient. K(phyllode) varied 18-fold and was positively correlated with primary nerve hydraulic conductance, and with primary nerve (vein) density but not with minor nerve density, in contrast with previous studies of true leaves in other dicotyledons. Phyllodes with higher primary nerve density also had greater mass per area (PMA) and larger bundle sheath extensions (BSEs) from their minor nerves. We suggest that higher primary nerve conductivity and density may decrease the distance travelled in the high-resistance extra-xylem pathways of the phyllode. Further, larger BSEs may increase the area available for dispersion of water from the xylem to the extra-xylem tissue. High PMA phyllodes were more common in acacias from areas receiving lower annual precipitation. Maximizing efficient water movement through phyllodes may be more important where rainfall is meagre and infrequent, explaining relationships between nerve patterns and the climates of origin in Australian phyllodinous Acacia.

Variation in snow cover drives differences in frost resistance in seedlings of the alpine herb Aciphylla glacialis

Publisher: Elsevier BV

Date: 10-2014

DOI: 10.1016/J.ENVEXPBOT.2014.02.011

Photosynthesis and growth of two rain forest species in simulated gaps under elevated CO₂

Publisher: Wiley

Date: 03-1997

DOI: 10.1890/0012-9658(1997)078[0385:PAGOTR]2.0.CO;2

Relative contributions of leaf area ratio and net assimilation rate to change in growth rate depend on growth temperature: comparative analysis of subantarctic and alpine grasses

Publisher: Wiley

Date: 08-05-2007

DOI: 10.1111/J.1469-8137.2007.02097.X

Abstract: The present study shows that the relative contributions of leaf area ratio (LAR) and net assimilation rate (NAR) to variation among species in relative growth rate (RGR) depend on growth temperature. We grew three subantarctic and three alpine Poa species at daytime temperatures of 7, 12 and 17 degrees C, and analysed interspecific and temperature-related variation in RGRs by growth analysis. Variation in NAR accounted for most of the interspecific differences in RGR at low growth temperature, whereas variation in both NAR and LAR contributed strongly to interspecific differences in RGR at high growth temperature. For most species, the increase in RGR from 7 to 12 degrees C was attributable to an increase in LAR, whereas the increase in RGR from 12 to 17 degrees C was attributable to an increase in NAR. There were no differences between native subantarctic and alpine species in the plasticity of growth responses to temperature. However, Poa annua, a species introduced to the subantarctic, showed much greater growth plasticity than other species. There was little difference among species in tolerance of high-temperature extremes.

Hydraulically based stomatal oscillations and stomatal patchiness in Gossypium hirsutum

Publisher: CSIRO Publishing

Date: 2006

DOI: 10.1071/FP06115

Abstract: Slow stomatal oscillations (70–95 min), associated with feedback within the plant hydraulic systems, were studied in cotton (Gossypium hirsutum L.). Oscillations were only evident when the whole plant was exposed to light, and were not influenced by reductions in intercellular CO2 concentrations (Ci) in intact, attached leaves. Oscillations were synchronised among different leaves of the same plant, even when the leaf-to-air vapour pressure difference (VPD) was reduced in a cuvette enclosing one of the leaves. In the trough phase of stomatal oscillations the apparent Ci was higher than expected from the combination of the observed assimilation rate and the A(Ci) relationship measured in the absence of oscillations. Using chlorophyll fluorescence imaging we found evidence of stomatal heterogeneity in this phase. Finally, we found that stomatal oscillations appeared to be correlated with xylem embolism, with more vessels filled with gas at the peak than at the troughs of stomatal oscillations.

Rapid hydraulic recovery in Eucalyptus pauciflora after drought: linkages between stem hydraulics and leaf gas exchange

Publisher: Wiley

Date: 09-09-2014

DOI: 10.1111/PCE.12182

Abstract: In woody plants, photosynthetic capacity is closely linked to rates at which the plant hydraulic system can supply water to the leaf surface. Drought-induced embolism can cause sharp declines in xylem hydraulic conductivity that coincide with stomatal closure and reduced photosynthesis. Recovery of photosynthetic capacity after drought is dependent on restored xylem function, although few data exist to elucidate this coordination. We examined the dynamics of leaf gas exchange and xylem function in Eucalyptus pauciflora seedlings exposed to a cycle of severe water stress and recovery after re-watering. Stomatal closure and leaf turgor loss occurred at water potentials that delayed the extensive spread of embolism through the stem xylem. Stem hydraulic conductance recovered to control levels within 6 h after re-watering despite a severe drought treatment, suggesting an active mechanism embolism repair. However, stomatal conductance did not recover after 10 d of re-watering, effecting tighter control of transpiration post drought. The dynamics of recovery suggest that a combination of hydraulic and non-hydraulic factors influenced stomatal behaviour post drought.

Leaf cooling curves: measuring leaf temperature in sunlight

Publisher: CSIRO Publishing

Date: 2006

DOI: 10.1071/FP05300

Abstract: Despite the obvious benefits of using thermography under field conditions, most infrared studies at the leaf level are generally conducted in the laboratory. One reason for this bias is that accuracy can potentially be compromised in sunlight because reflected radiation from the leaf might affect the calculation of the temperature measurement. We have developed a method for measuring leaf temperature in sunlight by using thermal imagery to generate cooling curves from which the time constant for cooling, τ, can be calculated. The original temperature of the sunlit leaf may be determined by extrapolating backwards in time. In the absence of specular reflection, there is close agreement between the extrapolated sunlit temperature and the sunlit temperature recorded by the camera. However, when reflected radiation is high, the difference between the initial (incorrect) temperature determined from the sunlit image and the temperature extrapolated from the cooling curve can be 2°C. Notably, our results demonstrate a close agreement between the extrapolated sunlit temperature and the temperature of the leaf approximately 1 s after being shaded, suggesting that this shaded image provides a good estimate of the original sunlit temperature. Thus, our technique provides two means for measuring leaf surface temperature in sunlight.

Shifting access to pools of shoot water sustains gas exchange and increases stem hydraulic safety during seasonal atmospheric drought

Publisher: Wiley

Date: 25-05-2021

DOI: 10.1111/PCE.14080

Abstract: Understanding how plants acclimate to drought is crucial for predicting future vulnerability, yet seasonal acclimation of traits that improve drought tolerance in trees remains poorly resolved. We hypothesized that dry season acclimation of leaf and stem traits influencing shoot water storage and hydraulic capacitance would mitigate the drought‐associated risks of reduced gas exchange and hydraulic failure in the mangrove Sonneratia alba . By late dry season, availability of stored water had shifted within leaves and between leaves and stems. While whole shoot capacitance remained stable, the symplastic fraction of leaf water increased 86%, leaf capacitance increased 104% and stem capacitance declined 80%. Despite declining plant water potentials, leaf and whole plant hydraulic conductance remained unchanged, and midday assimilation rates increased. Further, the available leaf water between the minimum water potential observed and that corresponding to 50% loss of stem conductance increased 111%. Shifting availability of pools of water, within and between organs, maintained leaf water available to buffer periods of increased photosynthesis and losses in stem hydraulic conductivity, mitigating risks of carbon depletion and hydraulic failure during atmospheric drought. Seasonal changes in access to tissue and organ water may have an important role in drought acclimation and avoidance.

Evergreen leaf respiration acclimates to long-term nocturnal warming under field conditions

Publisher: Wiley

Date: 06-2007

DOI: 10.1111/J.1365-2486.2007.01351.X

Cold-induced photoinhibition limits regeneration of snow gum at tree- line

Publisher: JSTOR

Date: 1991

DOI: 10.2307/2389486

Freeze/thaw-induced embolism: probability of critical bubble formation depends on speed of ice formation

Publisher: Frontiers Media SA

Date: 2012

DOI: 10.3389/FPLS.2012.00107

Transpiration by trees from contrasting forest types

Publisher: CSIRO Publishing

Date: 1996

DOI: 10.1071/BT9960249

Abstract: Temperate rainforests and eucalypt forests of coastal south-eastern Australia are distributed differentially with aspect. Rainforests, in which Ceratopetalum apetalum D.Don and Doryphora sassafras Endl. are the dominant tree species, occur on slopes of southerly aspect and along gully bottoms, whereas eucalypt forests, dominated by Eucalyptus maculata Hook., occur on upper slopes of northerly aspect and on ridge tops. Whether transpiration rates of trees differed across the rainforest-eucalypt forest boundary on north and south facing aspects was tested by measuring stem sap flow in trees in a single catchment during winter, summer and autumn. Differences in transpiration rate by trees in these stands were due to various combinations of biological and physical factors. Firstly, mean maximum transpiration rate per tree (crown area basis) was greater in rainforest on the gully bottom where deep soil water from down-slope drainage was greater than in eucalypt forest located upslope on the northern aspect. By contrast, there was no difference between maximum transpiration rates in rainforest and eucalypt forest on the southern aspect. Variation in transpiration rate between seasons was not related to variation in surface soil moisture content ( 0.35 m depth). Secondly, transpiration rates per unit crown area in rainforest at the gully bottom were associated with higher leaf area indices than upslope on the northern aspect. However, in rainforest upslope on the southern aspect, higher transpiration rates were not associated with higher leaf area indices. Thirdly, trees in eucalypt forest maintained similar sapwood moisture contents in summer as in winter and autumn, whereas sapwood moisture contents declined in rainforest trees in summer, suggesting that eucalypts had access to water from deep within the soil profile which was unavailable to more shallow rooting rainforest trees. Fourthly, higher modal and maximal sap velocities in eucalypt trees were partly due to wider xylem vessels and resulted in faster maximum sap flow and greater daily total water use in all seasons on both aspects than in rainforest species. Finally, as atmospheric demand for water increased from winter to summer, transpiration rates were mediated by stomata1 closure as indicated by lower average midday shoot conductance to water vapour during summer than other seasons. The interaction between microenvironment, which deteimines water availability, and physiological attsibutes, which determine tree water acquisition and use, may contribute to the differential distribution of rainforest and eucalypt forest with aspect in south-eastern Australia.

Do thick leaves avoid thermal damage in critically low wind speeds?

Publisher: Wiley

Date: 02-2012

DOI: 10.1111/J.1469-8137.2012.04058.X

Abstract: Transient lulls in air movement are rarely measured, but can cause leaf temperature to rise rapidly to critical levels. The high heat capacity of thick leaves can d this rapid change in temperature. However, little is known about the extent to which increased leaf thickness can reduce thermal damage, or how thick leaves would need to be to have biological significance. We evaluated quantitatively the contribution of small increases in leaf thickness to the reduction in thermal damage during critically low wind speeds under desert conditions. We employed a numerical model to investigate the effect of thickness relative to transpiration, absorptance and leaf size on damage avoidance. We used measured traits and thermotolerance thresholds of real leaves to calculate the leaf temperature response to naturally occurring variable low wind speed. Our results demonstrated that an increase in thickness of only fractions of a millimetre can prevent excursions to damaging high temperatures. This d ing effect of increased thickness was greatest when other means of reducing leaf temperature (transpiration, reflectance or reduced size) were lacking. For perennial desert flora, we propose that increased leaf thickness is important in decreasing the incidence of extreme heat stress and, in some species, in enhancing long-term survival.

Shoot surface water uptake enables leaf hydraulic recovery in Avicennia marina

Publisher: Wiley

Date: 17-09-2019

DOI: 10.1111/NPH.16126

Abstract: The significance of shoot surface water uptake (SSWU) has been debated, and it would depend on the range of conditions under which it occurs. We hypothesized that the decline of leaf hydraulic conductance (K

Variation in hydraulic conductivity of mangroves: influence of species, salinity, and nitrogen and phosphorus availability

Publisher: Wiley

Date: 07-2006

DOI: 10.1111/J.1399-3054.2006.00723.X

Patterns of secondary succession in a mangrove forest of Southern Florida

Publisher: Springer Science and Business Media LLC

Date: 1980

DOI: 10.1007/BF00572684

Nitrogen fertilization enhances water-use efficiency in a saline environment

Publisher: Wiley

Date: 03-2010

DOI: 10.1111/J.1365-3040.2009.02072.X

Abstract: Effects of salinity and nutrients on carbon gain in relation to water use were studied in the grey mangrove, Avicennia marina, growing along a natural salinity gradient in south-eastern Australia. Tall trees characterized areas of seawater salinities (fringe zone) and stunted trees dominated landward hypersaline areas (scrub zone). Trees were fertilized with nitrogen (+N) or phosphorus (+P) or unfertilized. There was no significant effect of +P on shoot growth, whereas +N enhanced canopy development, particularly in scrub trees. Scrub trees maintained greater CO(2) assimilation per unit water transpired (water-use efficiency, WUE) and had lower nitrogen-use efficiency (NUE CO(2) assimilation rate per unit leaf nitrogen) than fringe trees. The CO(2) assimilation rates of +N trees were similar to those in other treatments, but were achieved at lower transpiration rates, stomatal conductance and intercellular CO(2) concentrations. Maintaining comparable assimilation rates at lower stomatal conductance requires greater ribulose 1.5-bisphosphate carboxylase/oxygenase activity, consistent with greater N content per unit leaf area in +N trees. Hence, +N enhanced WUE at the expense of NUE. Instantaneous WUE estimates were supported by less negative foliar delta(13)C values for +N trees and scrub control trees. Thus, nutrient enrichment may alter the structure and function of mangrove forests along salinity gradients.

Frost tolerance and ice formation in Pinus radiata needles: ice management by the endodermis and transfusion tissues

Publisher: CSIRO Publishing

Date: 2009

DOI: 10.1071/FP08247

Abstract: Conifers are among the most frost tolerant tree species. Cryo-scanning electron microscopy (cryo-SEM) was used to visualise ice formation in pine needles to better understand how conifer leaves manage extracellular ice. Acclimated and unacclimated needles of Pinus radiata (D.Don) were subjected to freezing treatments (at a rate of 2°C h−1), tested for electrolyte leakage and s led for cryo-SEM analysis. Half maximal electrolyte leakage occurred at –4 and −12°C for unacclimated and acclimated needles, respectively. Ice nucleation occurred at similar temperatures (−3°C) in both acclimated and unacclimated pine needles, indicating that frost tolerance did not increase supercooling. During freezing and thawing, the tissues outside and inside the endodermis shrank and swelled independently, with little or no transfer of water between the two regions. During freezing, mesophyll cells shrank, exhibiting cytorrhysis, and extracellular ice accumulated in gas spaces of the mesophyll tissue. Mesophyll cells from acclimated needles recovered their structure after thawing, and unacclimated mesophyll showed significant damage. In the vascular cylinder, ice accumulated in transfusion tracheids which expanded to occupy areas made vacant by shrinkage of transfusion parenchyma, Strasburger cells and the endodermis. This behaviour was reversible in acclimated tissue, and may play an important role in the management of ice during freeze/thaw events.

Mangroves provide blue carbon ecological value at a low freshwater cost

Publisher: Springer Science and Business Media LLC

Date: 20-02-2018

DOI: 10.1038/S41598-022-21514-8

Abstract: “Blue carbon” wetland vegetation has a limited freshwater requirement. One type, mangroves, utilizes less freshwater during transpiration than adjacent terrestrial ecoregions, equating to only 43% (average) to 57% (potential) of evapotranspiration ( $$ET$$ ET ). Here, we demonstrate that comparative consumptive water use by mangrove vegetation is as much as 2905 kL H 2 O ha −1 year −1 less than adjacent ecoregions with $${E}_{c}$$ E c -to- $$ET$$ ET ratios of 47–70%. Lower porewater salinity would, however, increase mangrove $${E}_{c}$$ E c -to- $$ET$$ ET ratios by affecting leaf-, tree-, and stand-level eco-physiological controls on transpiration. Restricted water use is also additive to other ecosystem services provided by mangroves, such as high carbon sequestration, coastal protection and support of bio ersity within estuarine and marine environments. Low freshwater demand enables mangroves to sustain ecological values of connected estuarine ecosystems with future reductions in freshwater while not competing with the freshwater needs of humans. Conservative water use may also be a characteristic of other emergent blue carbon wetlands.

Sustained downregulation of photosystem II in mistletoes during winter depression of photosynthesis

Publisher: CSIRO Publishing

Date: 2002

DOI: 10.1071/FP02014

Abstract: Cold acclimation by sustained downregulation of PSII was studied in intact leaves of an Australian mistletoe Amyema miquelii (Lehm. ex Miq.) Tiegh. and its host Eucalyptus. The trends were followed from autumn to spring on leaves that had developed in summer and were exposed to different microclimates with progress of the seasons. In sun leaves of mistletoe, efficiency of excitation energy transfer from light-harvesting pigments to Chl a molecules in PSII core complexes was markedly reduced in winter. Concomitantly, a band in 77K fluorescence emission spectra emerged at 715 nm, in the same way as the cold-hard band found in overwintering snow gum seedlings (Gilmore and Ball 2000, Proceedings of the National Academy of Sciences USA 97, 11 098–11 101). Further, a distinct band, which presumably involves Chl-b-containing antennae complexes, appeared at 705 nm in –2°C fluorescence emission spectra with decreasing intensity of the PSII band. Much shorter PSII fluorescence lifetimes measured in sun leaves of mistletoe that were exhibiting sustained downregulation of PSII indicated enhanced thermal dissipation of excitation energy. Winter acclimation symptoms of the photosynthetic apparatus were more striking in mistletoe sun leaves compared with eucalypt sun leaves. Because the light and temperature environments of sun leaves are similar for the parasite and host, we primarily attribute the enhanced light-acclimation symptoms to the limited photosynthetic capacity of A. miquelii in winter.

Properties of thylakoid membranes of the mangroves, avicennia germinans and avicennia marina, and the sugar beet, beta vulgaris, grown under different salinity conditions

Publisher: Oxford University Press (OUP)

Date: 10-1984

DOI: 10.1104/PP.76.2.531

Applications of chlorophyll fluorescence to forest ecology

Publisher: CSIRO Publishing

Date: 1995

DOI: 10.1071/PP9950311

Abstract: Functioning of photosystem II (PSII) is the most sensitive indicator of environmental stress in plants. Changes in PSII activity can be assayed rapidly and non-destructively by measurement of chlorophyll fluorescence. While there have been many laboratory studies of chlorophyll fluorescence, fluorescence techniques have seldom been applied to questions in forest ecology. Most studies have emphasised the fluorescence parameter, Fv/Fm, which is well correlated with the quantum efficiency of photosynthetic carbon dioxide assimilation or oxygen evolution. This parameter reveals information which can be related to diurnal and seasonal variation in photosynthesis, plant growth and community dynamics. Thus, fluorescence techniques provide a powerful means of linking photosynthesis with higher levels of plant functioning and have great potential for research in forest ecology.

Preface

Publisher: CSIRO Publishing

Date: 1999

DOI: 10.1071/BTV47N4_PR

Abstract: This issue of Australian Journal of Botany sees the first in a new series of scholarly reviews to be called the .Turner Reviews. in honour of John Stewart Turner, Ph.D. (Cantab.), FAA (1908.1991). John Turner was Professor of Botany and Plant Physiology at The University of Melbourne from 1938 to 1973. He was a foundation member of the Advisory Committee of the Australian Journal of Botany. The present Advisory Committee initiated the Turner Reviews in recognition of Turner.s wide-reaching influences on several generations of botanists and conservationists in Australia (see Rowan and Ashton, this volume). The Turner Reviews aim to provide critical, state-of-the-art evaluations that advance our knowledge in current, key areas of botanical research. The Turner Reviews will be commissioned by invitation, and will be numbered in sequence. A number of free reprints in a distinctive cover will be provided free of charge to authors. A Reviews Subcommittee has been formed to select authors and to oversee the refereeing process. The members are Dr Peter Attiwill, Dr Marilyn Ball and Professor Byron Lamont. We would greatly appreciate advice and suggestions on prospective reviewers for this important new series. Peter Attiwill School of Botany The University of Melbourne Parkville, Vic. 3052 Phone 03 9344 5068 Fax 03 9344 6857 Email p.attiwill@botany.unimelb.edu.au Marilyn Ball Australian National University Research School of Biological Sciences GPO Box 475 Canberra ACT 0200 Phone 02 6249 5057 Fax 02 6249 5095 Email mball@rsbs-central.anu.edu.au Byron Lamont School of Environmental Biology Curtin University of Technology GPO Box U 1987 Perth WA 6001 Phone 08 9266 7784 Fax 08 9266 2495 Email rlamontb@cc.curtin.edu.au

Differential responses of the mangrove Avicennia marina to salinity and abscisic acid

Publisher: CSIRO Publishing

Date: 2012

DOI: 10.1071/FP12178

Abstract: Salinisation of the soil can cause plant water deficits, ion and nutrient imbalances and toxic reactions. The halophyte, Avicennia marina (Forssk.) Vierh., is a mangrove that tolerates a wide range of soil salinities. In order to understand how salinity affects plant growth and functioning and how salinity responses are influenced by the water deficit signalling hormone abscisic acid (ABA) we grew A. marina seedlings under two non-growth limiting salinities: 60% seawater and 90% seawater and with and without exogenously supplied ABA. We measured growth, photosynthesis, sap flow, aquaporin gene expression, hydraulic anatomy and nutrient status as well as sap ABA concentrations. ABA addition resulted in a drought phenotype (reduced sap flow, transpiration rates and photosynthesis and increased water use efficiency and aquaporin expression). In contrast, growth in high salinity did not lead to responses that are typical for water deficits, but rather, could be characterised as drought avoidance strategies (no reduction in sap flow, transpiration rates and photosynthesis and reduced aquaporin expression). Tissue nutrient concentrations were higher in seedlings grown at high salinities. We did not find evidence for a role for ABA in the mangrove salinity response, suggesting ABA is not produced directly in response to high concentrations of NaCl ions.

On the halophytic nature of mangroves

Publisher: Springer Science and Business Media LLC

Date: 05-09-2013

DOI: 10.1007/S00468-012-0767-7

Plant responses to salinity under elevated atmospheric concentrations of CO₂

Publisher: CSIRO Publishing

Date: 1992

DOI: 10.1071/BT9920515

Abstract: This review explores effects of elevated CO2 concentrations on growth in relation to water use and salt balance of halophytic and non-halophytic species. Under saline conditions, the uptake and distribution of sodium and chloride must be regulated to protect sensitive metabolic sites from salt toxicity. Salt-tolerant species exclude most of the salt from the transpiration stream, but the salt flux from a highly saline soil is still considerable. To maintain internal ion concentrations within physiologically acceptable levels, the salt influx to leaves must match the capacities of leaves for salt storage and/or salt export by either retranslocation or secretion from glands. Hence the balance between carbon gain and the expenditure of water in association with salt uptake is critical to leaf longevity under saline conditions. Indeed, one of the striking features of halophytic vegetation, such as mangroves, is the maintenance of high water use efficiencies coupled with relatively low rates of water loss and growth. These low evaporation rates are further reduced under elevated CO2 conditions. This, with increased growth, leads to even higher water use efficiency. Leaves of plants grown under elevated CO2 conditions might be expected to contain lower salt concentrations than those grown under ambient CO2 if salt uptake is coupled with water uptake. However, salt concentrations in shoot tissues are similar in plants grown under ambient and elevated CO2 conditions despite major differences in water use efficiency. This phenomenon occurs in C3 halophytes and in both C3 and C2 non-halophytes. These results imply shoot/root communication in regulation of the salt balance to adjust to environmental factors affecting the availability of water and ions at the roots (salinity) and those affecting carbon gain in relation to water loss at the leaves (atmospheric concentrations of water vapour and carbon dioxide).

Biocomplexity in Mangrove Ecosystems

Publisher: Annual Reviews

Date: 2010

DOI: 10.1146/ANNUREV.MARINE.010908.163809

Abstract: Mangroves are an ecological assemblage of trees and shrubs adapted to grow in intertidal environments along tropical coasts. Despite repeated demonstration of their economic and societal value, more than 50% of the world's mangroves have been destroyed, 35% in the past two decades to aquaculture and coastal development, altered hydrology, sea-level rise, and nutrient overenrichment. Variations in the structure and function of mangrove ecosystems have generally been described solely on the basis of a hierarchical classification of the physical characteristics of the intertidal environment, including climate, geomorphology, topography, and hydrology. Here, we use the concept of emergent properties at multiple levels within a hierarchical framework to review how the interplay between specialized adaptations and extreme trait plasticity that characterizes mangroves and intertidal environments gives rise to the biocomplexity that distinguishes mangrove ecosystems. The traits that allow mangroves to tolerate variable salinity, flooding, and nutrient availability influence ecosystem processes and ultimately the services they provide. We conclude that an integrated research strategy using emergent properties in empirical and theoretical studies provides a holistic approach for understanding and managing mangrove ecosystems.

Effect of salinity and humidity on δ¹³C value of halophytes-Evidence for diffusional isotope fractionation determined by the ratio of intercellular/atmospheric partial pressure of CO₂ under different environmental conditions

Publisher: Springer Science and Business Media LLC

Date: 1982

DOI: 10.1007/BF00349020

The Physiology of Mangrove Trees with Changing Climate

Publisher: Springer International Publishing

Date: 2016

DOI: 10.1007/978-3-319-27422-5_7

Non-destructive measurement of chlorophyll b : a ratios and identification of photosynthetic pathways in grasses by reflectance spectroscopy

Publisher: CSIRO Publishing

Date: 2009

DOI: 10.1071/FP09201

Abstract: Equations for non-destructive determination of chlorophyll b : a ratios in grasses were developed from reflectance spectra of intact leaves of barley (Hordeum vulgare L.) and two barley mutants: clorina f2, which lacks chlorophyll b and clorina f104, which has a low chlorophyll b content. These plants enabled separation of effects of chlorophyll composition on reflectance spectra due to differential light absorption by chlorophylls a and b and to measure the effects of chlorophyll b on the contribution of fluorescence emitted by chlorophyll a to the reflectance spectra. Indices developed from these data were then tested on growth chamber-grown leaves from six C3 and 17 C4 grass species (7 NAD-ME and 10 NADP-ME subtypes). We used the chlorophyll b : a ratio because the data were less skewed than the chlorophyll a : b ratio. The best index for determination of the chlorophyll b : a ratio utilised wavelengths affected by chlorophyll absorbance: [R626 – 0.5 (R603 + R647)]/[R552– R626]. The chlorophyll b : a ratio was significantly lower in the C4 than C3 grasses, but was not sufficient in itself to separate these two functional groups. However, because of differences in fluorescence characteristics, C3 and C4 species could be distinguished by an index based on wavelengths affected by chlorophyll fluorescence: [R696 to 709/R545 to 567].

Ecophysiology of mangroves

Publisher: Springer Science and Business Media LLC

Date: 11-1988

DOI: 10.1007/BF00196018

Maintenance of leaf temperature and the optimisation of carbon gain in relation to water loss in a tropical mangrove forest

Publisher: CSIRO Publishing

Date: 1988

DOI: 10.1071/PP9880263

Abstract: Properties and display of foliage were studied in relation to gas exchange characteristics of tropical mangrove species. Rates of assimilation of CO2 were maximal at leaf temperatures of approximately 30°C. The species operated with higher water use efficiencies than do most C3 species, and water-use characteristics became increasingly conservative with increase in the salinity tolerance of the species. Changes in three properties of leaves, i.e. inclination, area, and succulence, contributed to maintenance of leaf temperatures near air temperatures with minimal evaporative cooling. Interspecific differences in water-use characteristics, and their relationship to the maintenance of favourable leaf temperatures, could affect the competitive abilities of mangroves and the structure of mangrove forests.

Freeze/thaw-induced embolism depends on nadir temperature: The heterogeneous hydration hypothesis

Publisher: Wiley

Date: 21-02-2006

DOI: 10.1111/J.1365-3040.2005.01426.X

Abstract: Freeze/thaw-induced embolism was studied in leaves of field-grown snow gum (Eucalyptus pauciflora) subject to frequent morning frosts. Juvenile trees were grown in buried pots, brought to the laboratory at different stages of acclimation and subjected to simulated frost-freezes (at 2 degrees C h(-1)) to nadir temperatures of -3 or -6 degrees C, which snow gums commonly experience. Frost-frozen and subsequently thawed leaves were cryo-fixed to preserve the distribution of water and were then examined by cryo-scanning electron microscopy. No embolisms were found in leaves frozen to -3 degrees C and thawed. In contrast, 34% of vessels were embolized in thawed leaves that had been frozen to -6 degrees C. This difference was seen also in the extent of extracellular ice blocks in the mid-vein expansion zones in leaves frozen to -3 and -6 degrees C, which occupied 3 and 14% of the mid-vein area, respectively. While the proportion of embolism depended on nadir temperature, it was independent of season (and hence of acclimation state). From the observation that increased embolism at lower nadir temperature was related to the freeze-induced redistribution of water, we hypothesize that the dehydration of cell walls and cells caused by the redistribution exerts sufficient tension on xylem water to induce cavitation on thawing.

Relationships among RNA DNA ratio, growth and elemental stoichiometry in mangrove trees

Publisher: Wiley

Date: 16-09-2010

DOI: 10.1111/J.1365-2435.2010.01722.X

Interactive effects of salinity and irradiance on growth: implications for mangrove forest structure along salinity gradients

Publisher: Springer Science and Business Media LLC

Date: 08-02-2002

DOI: 10.1007/S00468-002-0169-3

Monitoring plant water status via static uniaxial compression of the leaf lamina

Publisher: Wiley

Date: 03-07-2022

DOI: 10.1111/PCE.14383

Abstract: Turgor pressure is an essential, but difficult to measure indicator of plant water status. Turgor has been quantified by localized compression of cells or tissues, but a simple method to perform these measurements is lacking. We hypothesized that changes in leaf turgidity can be monitored by uniaxially compressing the leaf lamina and measuring the mechanical stress under a constrained thickness (stress relaxation) and that changes in leaf water content can be monitored by measuring the leaf thickness under constant mechanical stress. Using a simple, custom‐built leaf squeeze‐flow rheometer, we performed different compression tests on leaves from 13 plant species. The mechanical stress measured during stress relaxation was correlated with leaf bulk turgor pressure ( R 2 0.95) and thus with balancing pressure ( R 2 0.94) the leaf thickness measured under constant mechanical stress was correlated with relative water content ( R 2 0.74). The coefficients of these relationships were related to the leaf bulk osmotic pressure at the turgor‐loss point. An idealized average‐cell model suggests that, under isothermal conditions, the stationary bulk modulus during compression is largely determined by the bulk osmotic pressure. Our study presents an inexpensive, accessible and automatable method to monitor plant water status noninvasively.

Freezing pattern and frost killing temperature of apple (Malus domestica) wood under controlled conditions and in nature

Publisher: Oxford University Press (OUP)

Date: 23-05-2012

DOI: 10.1093/TREEPHYS/TPS046

Abstract: The freezing pattern and frost killing temperatures of apple (Malus domestica Borkh.) xylem were determined by differential thermal analysis and infrared differential thermal analysis (IDTA). Results from detached or attached twigs in controlled freezing experiments and during natural field freezing of trees were compared. Non-lethal freezing of apoplastic water in apple xylem as monitored during natural winter frosts in the field occurred at -1.9 ± 0.4 °C and did not change seasonally. The pattern of whole tree freezing was variable and specific to the environmental conditions. On detached twigs high-temperature freezing exotherms (HTEs) occurred 2.8 K below the temperature observed under natural frosts in the field with a seasonal mean of -4.7 ± 0.5 °C. Microporous apple xylem showed freezing without a specific pattern within a few seconds in IDTA images during HTEs, which is in contrast to macroporous xylem where a 2D freezing pattern mirrors anatomical structures. The pith tissue always remained unfrozen. Increasing twig length increased ice nucleation temperature for increased twig diameter the effect was not significant. In attached twigs frozen in field portable freezing chambers, HTEs were recorded at a similar mean temperature (-4.6 ± 1.0 °C) to those for detached twigs. Upon lethal intracellular freezing of apple xylem parenchyma cells (XPCs) low-temperature freezing exotherms (LTEs) can be recorded. Low-temperature freezing exotherms determined on detached twigs varied significantly between a winter minimum of -36.9 °C and a summer maximum -12.7 °C. Within the temperature range wherein LTEs were recorded by IDTA in summer (-12.7 ± 0.5 to -20.3 ± 1.1 °C) various tiny clearly separated discontinuous freezing events could be detected similar to that in other species with contrasting XPC anatomy. These freezing events appeared to be initially located in the primary and only later in the secondary xylem. During the LTE no freezing events in the bark and central pith tissue were recorded. Attached twigs were exposed to various freezing temperatures at which LTEs occur. Even if 60% of XPCs were frost-damaged twigs were able to recuperate and showed full re-growth indicating a high regeneration capacity even after severe frost damage to XPCs.

The impact of a locust plague on mangroves of the arid Western Australia coast

Publisher: Cambridge University Press (CUP)

Date: 12-04-2012

DOI: 10.1017/S0266467412000041

Abstract: Mangroves generally grow in nutrient-poor environments and maintain high levels of productivity through unique adaptations for nutrient conservation (Reef et al . 2010). One such adaptation in mangroves is highly efficient resorption of limiting nutrients from senescing leaves prior to abscission (Feller et al . 2003). Thus processes that lead to loss of foliage prior to senescence and nutrient resorption (e.g. storms and herbivory) can be detrimental to tree growth and productivity (Bryant et al . 1983, May & Killingbeck 1992). Furthermore, decomposition of fallen leaves by soil microbial communities (Alongi 1994, Holguin et al . 2001) and crabs (Nagelkerken et al . 2008) is another important process contributing to the recycling of nutrients that are in short supply. Therefore, processes that lead to a substantial reduction in litterfall can have a strong negative effect on nutrient cycling and forest productivity. Mangroves have long been recognized as an important source of organic carbon (both particulate and dissolved) for the surrounding tropical coastal ecosystems (Bouillon et al . 2008, Kristensen et al . 2008). Thus, processes affecting litterfall in mangroves can affect the surrounding marine food webs.

Effects of growth temperature on photosynthetic gas exchange characteristics and hydraulic anatomy in leaves of two cold-climate Poa species

Publisher: CSIRO Publishing

Date: 2011

DOI: 10.1071/FP10023

Abstract: How plastic is hydraulic anatomy with growth temperature, and how does this relate to photosynthesis? These interrelationships were studied in subantarctic Poa foliosa Hook. f. and alpine Poa hothamensis Vickery grown under 7/4°C and 12/9°C day/night temperatures, reflecting summer temperatures in their respective habitats. Conduit radii were smaller in P. foliosa than in P. hothamensis, consistent with greater avoidance of freeze/thaw-induced embolism. Despite its origins in an environment with relatively little temperature variation, P. foliosa exhibited greater plasticity in hydraulic anatomy than P. hothamensis, increasing the size and density of conduits when grown under the warmer temperature regime. Both species had similar anatomical capacities for water transport when grown at 12/9°C, but stomatal conductance was lower in P. foliosa than P. hothamensis, suggesting hydraulic limitations not explained by leaf vascular anatomy. However, greater photosynthetic capacity and foliar nitrogen contents enabled P. foliosa to achieve the same assimilation rate as P. hothamensis under the 12/9°C growth conditions. Our results showed that nitrogen plays a central role in maintaining assimilation rates when constrained either by enzymatic activity at low temperatures or by hydraulic limitations at high temperatures and evaporative demands. Interspecific differences in nitrogen and water use may influence how subantarctic and alpine vegetation responds to climate warming.

Excitation energy flow at 77 K in the photosynthetic apparatus of overwintering evergreens

Publisher: Wiley

Date: 07-2003

DOI: 10.1046/J.1365-3040.2003.01026.X

Gender bias in clinical case reports: A cross-sectional study of the “big five” medical journals

Publisher: Public Library of Science (PLoS)

Date: 11-05-2017

DOI: 10.1371/JOURNAL.PONE.0177386

Freeze avoidance: a dehydrating moss gathers no ice

Publisher: Wiley

Date: 07-09-2010

DOI: 10.1111/J.1365-3040.2010.02178.X

Abstract: Using cryo-SEM with EDX fundamental structural and mechanical properties of the moss Ceratodon purpureus (Hedw.) Brid. were studied in relation to tolerance of freezing temperatures. In contrast to more complex plants, no ice accumulated within the moss during the freezing event. External ice induced desiccation with the response being a function of cell type water-filled hydroid cells cavitated and were embolized at -4 °C while parenchyma cells of the inner cortex exhibited cytorrhysis, decreasing to ∼ 20% of their original volume at a nadir temperature of -20 °C. Chlorophyll fluorescence showed that these winter acclimated mosses displayed no evidence of damage after thawing from -20 °C while GCMS showed that sugar concentrations were not sufficient to confer this level of freezing tolerance. In addition, differential scanning calorimetry showed internal ice nucleation occurred in hydrated moss at ∼-12 °C while desiccated moss showed no evidence of freezing with lowering of nadir temperature to -20 °C. Therefore the rapid dehydration of the moss provides an elegantly simple solution to the problem of freezing remove that which freezes.

Effect of elevated [CO₂] on photosynthesis and growth of snow gum (Eucalyptus pauciflora) seedlings during winter and spring

Publisher: CSIRO Publishing

Date: 1999

DOI: 10.1071/PP98134

Abstract: Snow gum (Eucalyptus pauciflora Sieb. ex Spreng.) seedlings were grown from autumn through spring in open top chambers located in a pasture naturally subject to freezing temperatures in either ambient or elevated (350 µL L-1 above ambient) CO2 concentrations. Sustained reduction in quantum efficiency, as measured by chlorophyll fluorescence (Fv/Fm), in over-wintering leaves may be related to seasonal down-regulation of photosynthesis, combined with cumulative effects of freeze- induced damage to the photosynthetic apparatus, with the effect being greater in leaves grown under elevated [CO2]. Down-regulation of photosynthesis apparently occurred in response to seasonal limitations to growth which were not overcome by elevation of [CO2] despite temperatures being favorable for photosynthesis during most of the photoperiod. Elevated [CO2] had no effect on growth of over-wintering seedlings, but enhanced growth in spring when minimum temperatures rose consistently above freezing. As there were no effects of elevated [CO2] on allocation, the stimulation of growth in spring was attributable to increase in net assimilation rates. Thus seasonal differences in photoinhibition were consistent with seasonal differences in the capacity for growth, with plants grown under elevated [CO2] having to dissipate more excess excitation energy over-winter.

Bark water uptake through lenticels increases stem hydration and contributes to stem swelling

Publisher: Wiley

Date: 09-10-2023

DOI: 10.1111/PCE.14733

Mechanisms of competition: thermal inhibition of tree seedling growth by grass

Publisher: Springer Science and Business Media LLC

Date: 10-2002

DOI: 10.1007/S00442-002-1044-Z

Abstract: The relative importance of thermal interference and competition for below-ground resources in the inhibition of tree seedling growth by grass was determined under field conditions. Snow gum (Eucalyptus pauciflora) seedlings were grown in bare soil or soil covered with either live grass or straw. Covering soil with straw produced thermal conditions in soil and air that were indistinguishable from those associated with live grass. In contrast, seedlings grown in bare soil experienced more rapid increase in soil temperatures during late winter and spring, less frequent and less severe frosts, and temperature maxima that more closely followed those of the atmosphere than seedlings growing in live grass or straw. After 1 year, seedlings in bare soil had four times the biomass of those grown in grass or straw. Inhibition of seedling growth by grass was attributed to alteration of the thermal environment which caused (1) seedlings to have a short growing season largely restricted to summer, (2) temporal separation in competition for resources with consumption of below-ground resources by grass in spring reducing availability of resources to support tree seedling growth in early summer, and (3) seedlings to be more subject to stress from temperature extremes. These results show that thermal interference plays a major role in interactions between plants.

Processes and mechanisms of coastal woody‐plant mortality

Publisher: Wiley

Date: 29-07-2022

DOI: 10.1111/GCB.16297

Abstract: Observations of woody plant mortality in coastal ecosystems are globally widespread, but the overarching processes and underlying mechanisms are poorly understood. This knowledge deficiency, combined with rapidly changing water levels, storm surges, atmospheric CO 2 , and vapor pressure deficit, creates large predictive uncertainty regarding how coastal ecosystems will respond to global change. Here, we synthesize the literature on the mechanisms that underlie coastal woody‐plant mortality, with the goal of producing a testable hypothesis framework. The key emergent mechanisms underlying mortality include hypoxic, osmotic, and ionic‐driven reductions in whole‐plant hydraulic conductance and photosynthesis that ultimately drive the coupled processes of hydraulic failure and carbon starvation. The relative importance of these processes in driving mortality, their order of progression, and their degree of coupling depends on the characteristics of the anomalous water exposure, on topographic effects, and on taxa‐specific variation in traits and trait acclimation. Greater inundation exposure could accelerate mortality globally however, the interaction of changing inundation exposure with elevated CO 2 , drought, and rising vapor pressure deficit could influence mortality likelihood. Models of coastal forests that incorporate the frequency and duration of inundation, the role of climatic drivers, and the processes of hydraulic failure and carbon starvation can yield improved estimates of inundation‐induced woody‐plant mortality.

Rapid collapse of a sub-Antarctic alpine ecosystem: the role of climate and pathogens

Publisher: Wiley

Date: 06-05-2015

DOI: 10.1111/1365-2664.12436

Elevated atmospheric [CO2] promotes frost damage in evergreen tree seedlings

Publisher: Wiley

Date: 06-1998

DOI: 10.1046/J.1365-3040.1998.00296.X

Low temperature effects on photosynthesis and growth of grapevine

Publisher: Wiley

Date: 07-2004

DOI: 10.1111/J.1365-3040.2004.01184.X

Assessment of photoprotection mechanisms of grapevines at low temperature

Publisher: CSIRO Publishing

Date: 2003

DOI: 10.1071/FP02114

Abstract: The photosynthetic response of grapevine leaves (Vitis vinifera L. cv. Riesling) to low temperature was studied in the field and laboratory. Light-saturated rates of photosynthetic electron transport were lower and non-photochemical energy dissipation was higher when leaves were subject to low morning temperatures than to high afternoon temperatures under field conditions. These responses to low temperatures occurred without sustained reduction of quantum efficiency of PSII as measured by the variable to maximum chlorophyll fluorescence yield ratio, Fv/Fm, after dark adaptation. The temperature dependence of light-saturated apparent electron transport rate, gas exchange and non-photochemical quenching (NPQ) was also examined in laboratory experiments with glasshouse-grown material. NPQ reached saturation at lower light intensity with decreasing temperature. The relationship between the quantum efficiency of PSII and CO2 fixation at 25°C (2–21% O2) and 10°C (2–21% O2) indicated a decreased dependence of electron transport on both photorespiration and the Mehler reaction at the lower temperature. The calculated percentage of electron flow to the Mehler reaction declined faster than photorespiration at low temperature. Warm- and cold-treated leaf discs under saturating light showed very little photoinhibition as measured by sustained reduction in Fv/Fm, which was linearly related to the percentage of functional PSII reaction centres. However, the addition of dithiothreitol greatly enhanced the rate of photoinhibition, indicating a potentially strong dependence on xanthophyll de-epoxidation for photoprotection at low temperature.

Foliar water uptake enables embolism removal in excised twigs of Avicennia marina

Publisher: Wiley

Date: 07-12-2023

DOI: 10.1111/NPH.18613

Abstract: Embolism refilling is thought to require relaxation of xylem tension, and it is unclear whether and how tall trees or plants growing in arid or saline soils recover from embolism. We tested whether foliar water uptake could enable embolism refilling in dehydrated twigs of the grey mangrove ( Avicennia marina ). Four dehydrated twigs were imaged by laboratory‐based micro‐computed tomography before and after wetting leaves. Emboli were observed in dehydrated stems and leaves. Embolism decreased with increasing distance from the cut end of stems, suggesting that stem emboli were caused by cutting. A significant ( P = 0.026) c . 80% reduction in the embolised area was observed in leaves between the start and the end of the experiment (29 ± 10 h after wetting). Embolus diameter was unaffected by wetting. Embolism refilling occurred slowly, in stems embolised by cutting and leaves embolised by cutting and/or dehydration. The lack of response of embolus diameter to wetting suggests that capillarity was not the main mechanism for refilling. Results show that excised twigs of A . marina are able to recover from embolism by absorption of atmospheric water and call for studies under natural conditions.

Linking water use efficiency with water use strategy from leaves to communities

Publisher: Wiley

Date: 12-10-2023

DOI: 10.1111/NPH.19308

Winter frost resistance of Pinus cembra measured in situ at the alpine timberline as affected by temperature conditions

Publisher: Oxford University Press (OUP)

Date: 18-10-2011

DOI: 10.1093/TREEPHYS/TPR103

Abstract: Winter frost resistance (WFR), midwinter frost hardening and frost dehardening potential of Pinus cembra L. were determined in situ by means of a novel low-temperature freezing system at the alpine timberline ecotone (1950 m a.s.l., Mt Patscherkofel, Innsbruck, Austria). In situ liquid nitrogen (LN₂)-quenching experiments should check whether maximum WFR of P. cembra belonging to the frost hardiest conifer group, being classified in US Department of Agriculture climatic zone 1, suffices to survive dipping into LN₂ (-196 °C). Viability was assessed in a field re-growth test. Maximum in situ WFR (LT₅₀) of leaves was <- 75 °C and that of buds was less (-70.3 °C), matching the lowest water contents. In midwinter, in situ freezing exotherms of leaves, buds and the xylem were often not detectable. Ice formed in the xylem at a mean of -2.8 °C and in leaves at -3.3 °C. In situ WFR of P. cembra was higher than that obtained on detached twigs, as reported earlier. In situ LN₂-quenching experiments were lethal in all cases even when twigs of P. cembra were exposed to an in situ frost hardening treatment (12 days at -20 °C followed by 3 days at -50 °C) to induce maximum WFR. Temperature treatments applied in the field significantly affected the actual WFR. In January a frost hardening treatment (21 days at -20 °C) led to a significant increase of WFR (buds: -62 °C to <- 70 °C leaves: -59.6 °C to -65.2 °C), showing that P. cembra was not at its specific maximum WFR. In contrast, simulated warm spells in late winter led to premature frost dehardening (buds: -32.6 °C to -10.2 °C leaves: -32.7 to -16.4 °C) followed by significantly earlier bud swelling and burst in late winter. Strikingly, both temperature treatments, either increased air temperature (+10.1 °C) or increased soil temperature (+6.5 °C), were similarly effective. This high readiness to frost harden and deharden in winter in the field must be considered to be of great significance for future winter survival of P. cembra. Determination of WFR in field re-growth tests appears to be a valuable tool for critically judging estimates of WFR obtained on detached twigs in an ecological context.

The Effect of Elevated [CO2] on Growth and Photosynthesis of Two Eucalyptus Species Exposed to High Temperatures and Water Deficits

Publisher: Oxford University Press (OUP)

Date: 07-1996

DOI: 10.1104/PP.111.3.909

Abstract: Two species of eucalyptus (Eucalyptus macrorhyncha and Eucalyptus rossii) were grown for 8 weeks in either ambient (350 [mu]L L-1) or elevated (700 [mu]L L-1) CO2 concentrations, either well watered or without water additions, and subjected to a daily, 3-h high-temperature (45[deg]C, maximum) and high-light (1250 [mu]mol photons m-2 s-1, maximum) stress period. Water-stressed seedlings of E. macrorhyncha had higher leaf water potentials when grown in elevated [CO2]. Growth analysis indicated that increased [CO2] may allow eucalyptus species to perform better during conditions of low soil moisture. A down-regulation of photosynthetic capacity was observed for seedlings grown in elevated [CO2] when well watered but not when water stressed. Well-watered seedlings grown in elevated [CO2] had lower quantum efficiencies as measured by chlorophyll fluorescence (the ratio of variable to maximal chlorophyll fluorescence [Fv/Fm]) than seedlings grown in ambient [CO2] during the high-temperature stress period. However, no significant differences in Fv/Fm were observed between CO2 treatments when water was withheld. The reductions in dark-adapted Fv/Fm for plants grown in elevated [CO2] were not well correlated with increased xanthophyll cycle photoprotection. However, reductions in the Fv/Fm were correlated with increased levels of nonstructural carbohydrates. The reduction in quantum efficiencies for plants grown in elevated [CO2] is discussed in the context of feedback inhibition of electron transport associated with starch accumulation and variation in sink strength.

CO₂ enrichment predisposes foliage of a eucalypt to freezing injury and reduces spring growth

Publisher: Wiley

Date: 12-2005

DOI: 10.1111/J.1365-3040.2005.01387.X

Nutrient Enrichment Increases Mortality of Mangroves

Publisher: Public Library of Science (PLoS)

Date: 19-05-2009

DOI: 10.1371/JOURNAL.PONE.0005600

Estimating daytime ecosystem respiration from eddy-flux data

Publisher: Elsevier BV

Date: 02-2011

DOI: 10.1016/J.BIOSYSTEMS.2010.10.007

Abstract: To understand what governs the patterns of net ecosystem exchange of CO₂, an understanding of factors influencing the component fluxes, ecosystem respiration and gross primary production is needed. In the present paper, we introduce an alternative method for estimating daytime ecosystem respiration based on whole ecosystem fluxes from a linear regression of photosynthetic photon flux density data vs. daytime net ecosystem exchange data at forest ecosystem level. This method is based on the principles of the Kok-method applied at leaf level for estimating daytime respiration. We demonstrate the method with field data and provide a discussion of the limitations of the method.

Ghosts of dry seasons past: Legacy of severe drought enhances mangrove salinity tolerance through coordinated cellular osmotic and elastic adjustments

Publisher: Wiley

Date: 07-05-2023

DOI: 10.1111/PCE.14604

Abstract: The incidence and severity of global mangrove mortality due to drought is increasing. Yet, little is understood of the capacity of mangroves to show long‐term acclimation of leaf water relations to severe drought. We tested for differences between mid‐dry season leaf water relations in two cooccurring mangroves, Aegiceras corniculatum and Rhizophora stylosa before a severe drought (a heatwave combined with low rainfall) and after its relief by the wet season. Consistent with ecological stress memory, the legacy of severe drought enhanced salinity tolerance in the subsequent dry season through coordinated adjustments that reduced the leaf water potential at the turgor loss point and increased cell wall rigidity. These adjustments enabled maintenance of turgor and relative water content with increasing salinity. As most canopy growth occurs during the wet season, acclimation to the ‘memory’ of higher salinity in the previous dry season enables greater leaf function with minimal adjustments, as long‐lived leaves progress from wet through dry seasons. However, declining turgor safety margins ‐ the difference between soil water potential and leaf water potential at turgor loss ‐ implied increasing limitation to water use with increasing salinity. Thus, plasticity in leaf water relations contributes fundamentally to mangrove function under varying salinity regimes.

Plumbing the depths: extracellular water storage in specialized leaf structures and its functional expression in a three-domain pressure –volume relationship

Publisher: Wiley

Date: 25-07-2017

DOI: 10.1111/PCE.12788

Abstract: A three-domain pressure-volume relationship (PV curve) was studied in relation to leaf anatomical structure during dehydration in the grey mangrove, Avicennia marina. In domain 1, relative water content (RWC) declined 13% with 0.85 MPa decrease in leaf water potential, reflecting a decrease in extracellular water stored primarily in trichomes and petiolar cisternae. In domain 2, RWC decreased by another 12% with a further reduction in leaf water potential to -5.1 MPa, the turgor loss point. Given the osmotic potential at full turgor (-4.2 MPa) and the effective modulus of elasticity (~40 MPa), domain 2 emphasized the role of cell wall elasticity in conserving cellular hydration during leaf water loss. Domain 3 was dominated by osmotic effects and characterized by plasmolysis in most tissues and cell types without cell wall collapse. Extracellular and cellular water storage could support an evaporation rate of 1 mmol m

Linking physiological processes with mangrove forest structure: phosphorus deficiency limits canopy development, hydraulic conductivity and photosynthetic carbon gain in dwarf Rhizophora mangle

Publisher: Wiley

Date: 21-02-2006

DOI: 10.1111/J.1365-3040.2005.01446.X

Abstract: Spatial gradients in mangrove tree height in barrier islands of Belize are associated with nutrient deficiency and sustained flooding in the absence of a salinity gradient. While nutrient deficiency is likely to affect many parameters, here we show that addition of phosphorus (P) to dwarf mangroves stimulated increases in diameters of xylem vessels, area of conductive xylem tissue and leaf area index (LAI) of the canopy. These changes in structure were consistent with related changes in function, as addition of P also increased hydraulic conductivity (Ks), stomatal conductance and photosynthetic assimilation rates to the same levels measured in taller trees fringing the seaward margin of the mangrove. Increased xylem vessel size and corresponding enhancements in stem hydraulic conductivity in P fertilized dwarf trees came at the cost of enhanced mid-day loss of hydraulic conductivity and was associated with decreased assimilation rates in the afternoon. Analysis of trait plasticity identifies hydraulic properties of trees as more plastic than those of leaf structural and physiological characteristics, implying that hydraulic properties are key in controlling growth in mangroves. Alleviation of P deficiency, which released trees from hydraulic limitations, reduced the structural and functional distinctions between dwarf and taller fringing tree forms of Rhizophora mangle.

Spatial patterning of pigmentation in evergreen leaves in response to freezing stress

Publisher: Wiley

Date: 20-10-2003

DOI: 10.1046/J.1365-3040.2003.01106.X

Interactive effects of climate and nutrient enrichment on patterns of herbivory by different feeding guilds in mangrove forests

Publisher: Wiley

Date: 28-09-2017

DOI: 10.1111/GEB.12644

Structural changes in acclimated and unacclimated leaves during freezing and thawing

Publisher: CSIRO Publishing

Date: 2004

DOI: 10.1071/FP03164

Abstract: Freeze-induced damage to leaf tissues was studied at different states of acclimation to low temperatures in snow gum, Eucalyptus pauciflora Sieber ex Sprengel. Intact, attached leaves of plants grown under glasshouse or field conditions were frozen at natural rates (frost-freezing) and thawed under laboratory conditions. Leaves were cryo-fixed unfrozen, during frost-freezing or after thawing for observation in a cryo-scanning electron microscope. Frost-freezing in unacclimated tissues caused irreversible tissue damage consistent with tissue death. Intracellular ice formed in the cambium and phloem, killing the cells and leaving persistent gaps between xylem and phloem. Many other cells were damaged by frost-freeze-induced dehydration and failed to resorb water from thawed extracellular ice, leaving substantial amounts of liquid water in intercellular spaces. In contrast, acclimated leaves showed reversible tissue displacements consistent with leaf survival. In these leaves during freezing, massive extracellular ice formed in specific expansion zones within the midvein. On thawing, water was resorbed by living cells, restoring the original tissue shapes. Possible evolutionary significance of these expansion zones is discussed. Acclimated leaves showed no evidence of intracellular freezing, nor tissue lesions caused by extracellular ice. While the observations accord with current views of freeze-sensitivity and tolerance, cryo-microscopy revealed erse responses in different tissue types.

Cold-induced photoinhibition and design of shelters for establishment of eucalypts in pasture

Publisher: CSIRO Publishing

Date: 1994

DOI: 10.1071/BT9940139

Abstract: Juvenile Eucalyptus polyanthemos Schau. which had been established in an open pasture, were surrounded by in idual shelters made of different materials: chicken wire, white translucent plastic, and three types of shade cloth transmitting 30, 50 or 70% of incident sunlight. Air temperatures within white plastic shelters were up to 6°C above ambient air temperatures, whereas air temperatures in other shelters differed little from ambient. Irradiance was the main factor which varied between shelters. Leaves were photoinhibited over winter as shown by depression in pre-dawn Fv/Fm. The extent of that decrease in Fv/Fm was directly proportional to irradiance. Pre-dawn Fv/Fm recovered in all treatments during spring. Growth, as measured by stem elongation. occurred to a limited extent during winter, but primarily during spring. During both seasons, stem elongation was greatest in plants sheltered by 50% shadecloth. However, treatment-induced variation in stem elongation during spring was correlated with pre-dawn values for Fv/Fm measured during the previous winter. Reducing sunlight by 50% thus appeared to effect the best compromise between conflicting demands for protection from cold-induced photoinhibition during winter and for absorption of sufficient light for growth during spring.

Seasonal patterns of leaf gas exchange and water relations in dry rain forest trees of contrasting leaf phenology

Publisher: Oxford University Press (OUP)

Date: 05-2006

DOI: 10.1093/TREEPHYS/26.5.657

Abstract: Diurnal and seasonal patterns of leaf gas exchange and water relations were examined in tree species of contrasting leaf phenology growing in a seasonally dry tropical rain forest in north-eastern Australia. Two drought-deciduous species, Brachychiton australis (Schott and Endl.) A. Terracc. and Cochlospermum gillivraei Benth., and two evergreen species, Alphitonia excelsa (Fenzal) Benth. and Austromyrtus bidwillii (Benth.) Burret. were studied. The deciduous species had higher specific leaf areas and maximum photosynthetic rates per leaf dry mass in the wet season than the evergreens. During the transition from wet season to dry season, total canopy area was reduced by 70-90% in the deciduous species and stomatal conductance (g(s)) and assimilation rate (A) were markedly lower in the remaining leaves. Deciduous species maintained daytime leaf water potentials (Psi(L)) at close to or above wet season values by a combination of stomatal regulation and reduction in leaf area. Thus, the timing of leaf drop in deciduous species was not associated with large negative values of daytime Psi(L) (greater than -1.6 MPa) or predawn Psi(L) (greater than -1.0 MPa). The deciduous species appeared sensitive to small perturbations in soil and leaf water status that signalled the onset of drought. The evergreen species were less sensitive to the onset of drought and g(s) values were not significantly lower during the transitional period. In the dry season, the evergreen species maintained their canopies despite increasing water-stress however, unlike Eucalyptus species from northern Australian savannas, A and g(s) were significantly lower than wet season values.

Evaluation of the heat pulse velocity technique for measurement of sap flow in rainforest and eucalypt forest species of south‐eastern Australia

Publisher: Wiley

Date: 04-1995

DOI: 10.1111/J.1365-3040.1995.TB00381.X

Plant hydraulics as a central hub integrating plant and ecosystem function: meeting report for ‘Emerging Frontiers in Plant Hydraulics’ (Washington, DC, May 2015)

Publisher: Wiley

Date: 20-07-2016

DOI: 10.1111/PCE.12732

Abstract: Water plays a central role in plant biology and the efficiency of water transport throughout the plant affects both photosynthetic rate and growth, an influence that scales up deterministically to the productivity of terrestrial ecosystems. Moreover, hydraulic traits mediate the ways in which plants interact with their abiotic and biotic environment. At landscape to global scale, plant hydraulic traits are important in describing the function of ecological communities and ecosystems. Plant hydraulics is increasingly recognized as a central hub within a network by which plant biology is connected to palaeobiology, agronomy, climatology, forestry, community and ecosystem ecology and earth-system science. Such grand challenges as anticipating and mitigating the impacts of climate change, and improving the security and sustainability of our food supply rely on our fundamental knowledge of how water behaves in the cells, tissues, organs, bodies and erse communities of plants. A workshop, 'Emerging Frontiers in Plant Hydraulics' supported by the National Science Foundation, was held in Washington DC, 2015 to promote open discussion of new ideas, controversies regarding measurements and analyses, and especially, the potential for expansion of up-scaled and down-scaled inter-disciplinary research, and the strengthening of connections between plant hydraulic research, allied fields and global modelling efforts.

Light use in relation to carbon gain in the mangrove, Avicennia marina, under hypersaline conditions

Publisher: CSIRO Publishing

Date: 1999

DOI: 10.1071/PP98075

Abstract: Photosynthesis was studied in relation to light use in the mangrove, Avicennia marina (Forsk.) Vierh. var. australasica (Walp.) Moldenke, growing under soil salinities equivalent to one and two times seawater (i.e. 35 and 60‰). Midday CO2 assimilation rates averaged 7.6 0.7 and 4.3 0.3 µmol m–2 s–1 at the seawater and hypersaline sites, respectively. Despite this difference, xanthophyll pool sizes per Chl and epoxidation states were similar at both sites. Non-photochemical quenching also indicated comparable energy dissipation from pigment beds. Electron transport rates calculated from fluorescence characteristics were also similar and exceeded the requirements to sustain measured assimilation rates. However, cell wall conductance was low in seawater plants (75 mmol m2 s–1 ) and declined to 40 mmol m–2 s–1 in hypersaline plants. This would cause CO2 concentrations in chloroplasts (Cc ) to be lower than expected from measurements of intercellular CO2 concentrations (Ci ). In seawater plants, Cc was estimated to be 144 µmol mol–1 when Ci was 245 mmol mol–1, while values for Cc and Ci in hypersaline plants were 78 and 212 mmol mol–1, respectively. Reductions in Cc would enhance rates of photorespiration relative to assimilation, with the higher photorespiratory rates being sufficient to account for apparent excess electron transport rates.

Testing the Growth Rate vs. Geochemical Hypothesis for latitudinal variation in plant nutrients

Publisher: Wiley

Date: 10-10-2007

DOI: 10.1111/J.1461-0248.2007.01112.X

Abstract: Two hypotheses have been proposed to explain increases in plant nitrogen (N) and phosphorus (P) concentrations with latitude: (i) geochemical limitation to P availability in the tropics and (ii) temperature driven variation in growth rate, where greater growth rates (requiring greater nutrient levels) are needed to complete growth and reproduction within shorter growing seasons in temperate than tropical climates. These two hypotheses were assessed in one forest type, intertidal mangroves, using fertilized plots at sites between latitudes 36 masculine S and 27 masculine N. The N and P concentrations in mangrove leaf tissue increased with latitude, but there were no trends in N : P ratios. Growth rates of trees, adjusted for average minimum temperature showed a significant increase with latitude supporting the Growth Rate Hypothesis. However, support for the Geochemical Hypothesis was also strong both photosynthetic P use efficiency and nutrient resorption efficiency decreased with increasing latitude, indicating that P was less limiting to metabolism at the higher latitudes. Our study supports the hypothesis that historically low P availability in the tropics has been an important selective pressure shaping the evolution of plant traits.

A comparative study of the effects of NaCl salinity on respiration, photosynthesis, and leaf extension growth in Beta vulgaris L. (sugar beet)

Publisher: Wiley

Date: 11-1983

DOI: 10.1111/1365-3040.EP11589273

Disturbance is required for CO2-dependent promotion of woody plant growth in grasslands

Publisher: CSIRO Publishing

Date: 2010

DOI: 10.1071/FP09257

Abstract: The relative effects of disturbance (here defined as bare soil), competition for edaphic resources, thermal interference and elevated [CO2] on growth of tree seedlings in grasslands were studied under field conditions. Snow gum (Eucalyptus pauciflora Sieb. ex Spreng.) seedlings were grown in open-top chambers flushed with either ambient or elevated [CO2] from March 2004 to January 2005 (autumn to summer). These seedlings were planted into three treatments (i.e. bare soil, soil covered with straw or soil supporting a sward of live pasture grass) to separate effects of grass on seedling growth into those due to competition with grass for soil resources or to alteration of the thermal environment caused by a grassy surface (Ball et al. 2002). After the first major autumn frost, seedlings growing in competition with grass lost 59% of their canopy area, whereas those growing in bare soil or straw suffered negligible damage. These results reveal the complexity of competitive inhibition of plant growth in which ineffective competition for resources such as soil water enhances the vulnerability of the plant to abiotic stress, in this case frost. Tree seedlings growing in bare soil and straw commenced growth earlier in spring than those growing in competition with grass, where soil moisture was consistently lowest. Under ambient [CO2], growth was greater in bare soil than in straw, consistent with thermal interference, but these differences disappeared under elevated [CO2]. Elevated [CO2] significantly increased biomass accumulation for seedlings growing in bare soil and straw treatments, but not in grass. Thus, elevated [CO2] alleviated apparent thermal interference of seedling growth in spring but did not overcome adverse effects on seedling growth of either competitive reduction in soil resources or competitive enhancement of environmental stress. Nevertheless, elevated [CO2] could promote invasion of grasslands due to enhancement of woody plant growth in bare soil created by disturbances.

Cold-induced photoinhibition and growth of seedling snow gum (Eucalyptus pauciflora) under differing temperature and radiation regimes in fragmented forests

Publisher: Wiley

Date: 04-1998

DOI: 10.1046/J.1365-3040.1998.00291.X

Night and day: Shrinking and swelling of stems of diverse mangrove species growing along environmental gradients

Publisher: Public Library of Science (PLoS)

Date: 03-09-2019

DOI: 10.1371/JOURNAL.PONE.0221950

Growth and water use of the mangroves Rhizophora apiculata and R. stylosa in response to salinity and humidity under ambient and elevated concentrations of atmospheric CO₂

Publisher: Wiley

Date: 09-1997

DOI: 10.1046/J.1365-3040.1997.D01-144.X

Mangrove species richness in relation to salinity and waterlogging: a case study along the Adelaide River floodplain, northern Australia

Publisher: JSTOR

Date: 1998

DOI: 10.2307/2997699

Isotopic signatures of stem water reveal differences in water sources accessed by mangrove tree species

Publisher: Springer Science and Business Media LLC

Date: 08-03-2017

DOI: 10.1007/S10750-017-3149-8

Compensation for herbivory by Cucumis sativus through increased photosynthetic capacity and efficiency

Publisher: Springer Science and Business Media LLC

Date: 2003

DOI: 10.1007/S00442-002-1102-6

Abstract: Herbivory is an important selective pressure in the life history of most plant species, as it usually results in reduced plant fitness. In some situations, however, plants are able to compensate for the resources lost to herbivory and do not suffer any reduction in growth or reproduction after attack. We examined the ability of Lebanese cucumber (Cucumis sativus) to compensate for both pre-flowering and during-flowering foliar herbivory through increased photosynthetic efficiency and capacity. Plants that were damaged before flowering were able to compensate, in terms of vegetative biomass and fruit production for up to 80% leaf area loss. Plants that were damaged during the flowering period were less able to compensate and fruit production declined with increasing herbivory. Damaged plants had higher photosynthetic efficiency and capacity, and dissipated less light energy as heat. Herbivore-damaged plants may be induced to use a greater proportion of the absorbed light energy for photosynthesis as a result of altered carbohydrate source-sink relationships.

Easy Come, Easy Go: Capillary Forces Enable Rapid Refilling of Embolized Primary Xylem Vessels

Publisher: Oxford University Press (OUP)

Date: 19-06-2015

DOI: 10.1104/PP.15.00333

Growth and photosynthesis of two eucalypt species during high temperature stress under ambient and elevated [CO₂]

Publisher: Wiley

Date: 04-1996

DOI: 10.1111/J.1365-2486.1996.TB00056.X

Harvesting water from unsaturated atmospheres: deliquescence of salt secreted onto leaf surfaces drives reverse sap flow in a dominant arid climate mangrove, Avicennia marina

Publisher: Wiley

Date: 12-06-2021

DOI: 10.1111/NPH.17461

Abstract: The mangrove Avicennia marina adjusts internal salt concentrations by foliar salt secretion. Deliquescence of accumulated salt causes leaf wetting that may provide a water source for salt‐secreting plants in arid coastal wetlands where high nocturnal humidity can usually support deliquescence whereas rainfall events are rare. We tested the hypotheses that salt deliquescence on leaf surfaces can drive top‐down rehydration, and that such absorption of moisture from unsaturated atmospheres makes a functional contribution to dry season shoot water balances. Sap flow and water relations were monitored to assess the uptake of atmospheric water by branches during shoot wetting events under natural and manipulated microclimatic conditions. Reverse sap flow rates increased with increasing relative humidity from 70% to 89%, consistent with function of salt deliquescence in harvesting moisture from unsaturated atmospheres. Top‐down rehydration elevated branch water potentials above those possible from root water uptake, subsidising transpiration rates and reducing branch vulnerability to hydraulic failure in the subsequent photoperiod. Absorption of atmospheric moisture harvested through deliquescence of salt on leaf surfaces enhances water balances of Avicennia marina growing in hypersaline wetlands under arid climatic conditions. Top‐down rehydration from these frequent, low intensity wetting events contributes to prevention of carbon starvation and hydraulic failure during drought.

Factors influencing biodiversity and distributional gradients in mangroves

Publisher: JSTOR

Date: 1998

DOI: 10.2307/2997695

Microclimate above grass adversely affects spring growth of seedling snow gum (Eucalyptus pauciflora)

Publisher: Wiley

Date: 02-1997

DOI: 10.1046/J.1365-3040.1997.D01-61.X

Abstract: Growth of snow gum seedlings ( Eucalyptus pauciflora Sieb. ex Spreng.) was studied in response to differences in microclimate caused by differential heat exchange between seedlings, grass and bare, moist soil during winter and spring. Seedlings were planted in a pasture either directly into grassy groundcover or in circular patches of bare soil of 30, 60 or 120 cm in diameter. There were no differences in maximum air temperatures at seedling leaf height between treatments. However, minimum air temperature increased by 2 °C with increase in patch diameter from 0 to 120 cm such that seedlings surrounded by grass experienced lower minimum temperatures with more frequent and more severe frosts than seedlings growing in large patches of bare soil. These small‐scale differences in minimum temperature affected both photosynthetic and growth processes. Over winter, seedlings were photoinhibited, with depression in midday F v / F m linearly related to minimum temperatures. In spring, repeated frosts and lower minimum temperatures led to a delay in the recovery of F v / F m , a delay in bud‐break, damage to elongating stems and developing leaves, lower rates of stem elongation, and ultimately a shorter growing season for seedlings in grass compared to those in bare soil patches. Thus, microclimate above grass adversely affects spring growth of juvenile Eucalyptus pauciflora and may account for much of the competitive inhibition of tree seedling growth by grass during spring.

Leaf water storage increases with salinity and aridity in the mangrove Avicennia marina: integration of leaf structure, osmotic adjustment and access to multiple water sources

Publisher: Wiley

Date: 20-06-2017

DOI: 10.1111/PCE.12962

Abstract: Leaf structure and water relations were studied in a temperate population of Avicennia marina subsp. australasica along a natural salinity gradient [28 to 49 parts per thousand (ppt)] and compared with two subspecies grown naturally in similar soil salinities to those of subsp. australasica but under different climates: subsp. eucalyptifolia (salinity 30 ppt, wet tropics) and subsp. marina (salinity 46 ppt, arid tropics). Leaf thickness, leaf dry mass per area and water content increased with salinity and aridity. Turgor loss point declined with increase in soil salinity, driven mainly by differences in osmotic potential at full turgor. Nevertheless, a high modulus of elasticity (ε) contributed to maintenance of high cell hydration at turgor loss point. Despite similarity among leaves in leaf water storage capacitance, total leaf water storage increased with increasing salinity and aridity. The time that stored water alone could sustain an evaporation rate of 1 mmol m

Growth responses of the mangrove Avicennia marina to salinity: development and function of shoot hydraulic systems require saline conditions

Publisher: Oxford University Press (OUP)

Date: 19-01-2015

DOI: 10.1093/AOB/MCU257

Facilitation of seedling establishment: Reduction in irradiance enhances winter growth of Eucalyptus pauciflora

Publisher: Wiley

Date: 05-2000

DOI: 10.1890/0012-9658(2000)081[1437:FOSERI]2.0.CO;2

A model of frost impacts on seasonal photosynthesis of Eucalyptus pauciflora

Publisher: CSIRO Publishing

Date: 1998

DOI: 10.1071/PP97098

Abstract: A model of the time course of frost impacts on seasonal photosynthesis of Eucalyptus pauciflora Sieb. ex Spreng. was constructed, incorporating seasonal shifts in frost hardiness and both short- and long-term impacts on the initial slope and saturated level of the photosynthetic light response curve. The approach is an extension of Sands’ model (Australian Journal of Plant Physiology, 1995, 22, 603–614) which calculates daily canopy photosynthesis as a function of daily irradiance and temperatures without the impacts of cold nights. Modelled effects of frost on cumulative photosynthesis over 8 months were highly nonlinear and rather sensitive to the temporal sequence of minimum temperatures and extent of frost hardening. Most of the effects were associated with long-term damage caused by a few severe or unseasonal frosts. Shifting either plant sensitivity or minimum temperatures by several degrees had large impacts on predicted outcomes. These results are consistent with other observations that the increase in frost severity associated with land clearing is impeding eucalypt regeneration in interior Australia and may be applicable to other frost-prone areas.

Mangrove dieback during fluctuating sea levels

Publisher: Springer Science and Business Media LLC

Date: 10-05-2017

DOI: 10.1038/S41598-017-01927-6

Abstract: Recent evidence indicates that climate change and intensification of the El Niño Southern Oscillation (ENSO) has increased variation in sea level. Although widespread impacts on intertidal ecosystems are anticipated to arise from the sea level seesaw associated with climate change, none have yet been demonstrated. Intertidal ecosystems, including mangrove forests are among those ecosystems that are highly vulnerable to sea level rise, but they may also be vulnerable to sea level variability and extreme low sea level events. During 16 years of monitoring of a mangrove forest in Mangrove Bay in north Western Australia, we documented two forest dieback events, the most recent one being coincident with the large-scale dieback of mangroves in the Gulf of Carpentaria in northern Australia. Diebacks in Mangrove Bay were coincident with periods of very low sea level, which were associated with increased soil salinization of 20–30% above pre-event levels, leading to canopy loss, reduced Normalized Difference Vegetation Index (NDVI) and reduced recruitment. Our study indicates that an intensification of ENSO will have negative effects on some mangrove forests in parts of the Indo-Pacific that will exacerbate other pressures.

Hydraulic architecture of deciduous and evergreen dry rainforest tree species from north-eastern Australia

Publisher: Springer Science and Business Media LLC

Date: 09-12-2005

DOI: 10.1007/S00468-004-0392-1

Acclimation of snow gum (Eucalyptus pauciflora) leaf respiration to seasonal and diurnal variations in temperature: The importance of changes in the capacity and temperature sensitivity of respiration

Publisher: Wiley

Date: 2000

DOI: 10.1046/J.1365-3040.2000.00511.X

Growth responses to salinity in relation to distribution of two mangrove species, Sonneratia alba and S.lanceolata, in northern Australia

Publisher: JSTOR

Date: 02-1995

DOI: 10.2307/2390093

Water use efficiency in mangroves: Conservation of water use efficiency determined by stomatal behavior across leaves, plants, and forests

Publisher: Elsevier

Date: 2022

DOI: 10.1016/BS.ABR.2022.02.017

Measurement of plant water status via static uniaxial compression of the leaf lamina

Publisher: Cold Spring Harbor Laboratory

Date: 30-03-2022

DOI: 10.1101/2022.03.29.486324

Abstract: Turgor pressure is an essential, but difficult to measure indicator of plant water status. Turgor has been quantified by localised compression of cells or tissues, but a simple method to perform these measurements is lacking. We hypothesized that changes in leaf turgor pressure can be monitored by uniaxially compressing the leaf lamina and measuring the mechanical stress under a constrained thickness (stress relaxation) and that changes in leaf water content can be monitored by measuring the thickness of the leaf lamina compressed under a constant force (creep). Using a custom-built leaf squeeze-flow rheometer, we performed different compression tests on leaves from thirteen plant species. The equilibrium mechanical stress measured during stress relaxation was correlated with leaf turgor pressure (R 2 0.95) and thus with leaf water potential (R 2 0.94) the equilibrium leaf thickness measured during creep was correlated with relative water content (R 2 0.74). The coefficients of these relationships were related to the leaf osmotic pressure at the turgor-loss point. An idealised average-cell model suggests that, under isothermal conditions, the bulk cell stiffness during compression is largely determined by the leaf osmotic pressure. Our study presents an inexpensive, accessible and automatable method to monitor plant water status non-invasively.

Leaf shape influences spatial variation in photosynthetic function in Lomatia tinctoria

Publisher: CSIRO Publishing

Date: 2014

DOI: 10.1071/FP13334

Abstract: A relationship exists between the two-dimensional shape of leaves and their venation architecture, such that broad or broad-lobed leaves can have leaf tissue far from major veins, potentially creating stronger gradients in water potential – and associated photosynthetic function – than found across narrow counterparts. We examined the spatial patterns of photosynthetic efficiency (ΔF/Fm′) and non-photochemical quenching (NPQ) in response to increased vapour pressure deficit (VPD) using two morphs of Lomatia tinctoria (Labill.) R.Br: those with broad-lobed and those with narrow-lobed leaves. Stomatal conductance (gs), instantaneous water use efficiency (WUE), stomatal and minor veins density also were measured. ΔF/Fm′ decreased with stress but was higher and less spatially heterogeneous across broad than narrow lobes. The strongest depression in ΔF/Fm′ in broad lobes was at the edges and in narrow lobes, the tips. Non-photochemical quenching was spatially more varied in broad lobes, increasing at the edges and tips. Variation in photosynthetic function could not be explained by gs, WUE or minor vein density, whereas proximity to major veins appeared to mitigate water stress at the tips only for broad lobes. Our findings indicate that the relationship between venation architecture and water delivery alone can partially explain the spatial pattern of photosynthetic function.

Australian National University

Location: Australia

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Discovery Projects - Grant ID: DP110105380

Start Date: 2011

End Date: 12-2014

Amount: $315,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP180102969

Start Date: 05-2018

End Date: 12-2021

Amount: $368,400.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP0452526

Start Date: 2004

End Date: 12-2007

Amount: $240,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP0881009

Start Date: 04-2008

End Date: 07-2011

Amount: $318,000.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE100100078

Start Date: 2010

End Date: 12-2010

Amount: $600,000.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE0668487

Start Date: 2006

End Date: 12-2007

Amount: $553,000.00

Funder: Australian Research Council

Research Networks - Grant ID: RN0459908

Start Date: 12-2004

End Date: 09-2010

Amount: $2,500,000.00

Funder: Australian Research Council

Special Research Initiatives - Grant ID: SR0354582

Start Date: 2003

End Date: 12-2003

Amount: $20,000.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP0214956

Start Date: 12-2002

End Date: 12-2009

Amount: $887,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP150104437

Start Date: 06-2015

End Date: 06-2018

Amount: $428,900.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP1096749

Start Date: 2010

End Date: 12-2012

Amount: $326,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP0774491

Start Date: 2007

End Date: 06-2010

Amount: $263,000.00

Funder: Australian Research Council