John Evans

Phosphorus status determines biomass response to elevated CO₂ in a legume : C₄ grass community

Publisher: Wiley

Date: 13-10-2005

DOI: 10.1111/J.1365-2486.2005.1049.X

Using tunable diode laser spectroscopy to measure carbon isotope discrimination and mesophyll conductance to CO₂ diffusion dynamically at different CO₂ concentrations

Publisher: Wiley

Date: 21-01-2011

DOI: 10.1111/J.1365-3040.2010.02264.X

Abstract: In C₃ leaves, the mesophyll conductance to CO₂ diffusion, g(m) , determines the drawdown in CO₂ concentration from intercellular airspace to the chloroplast stroma. Both g(m) and stomatal conductance limit photosynthetic rate and vary in response to the environment. We investigated the response of g(m) to changes in CO₂ in two Arabidopsis genotypes (including a mutant with open stomata, ost1), tobacco and wheat. We combined measurements of gas exchange with carbon isotope discrimination using tunable diode laser absorption spectroscopy with a CO₂ calibration system specially designed for a range of CO₂ and O₂ concentrations. CO₂ was initially increased from 200 to 1000 ppm and then decreased stepwise to 200 ppm and increased stepwise back to 1000 ppm, or the sequence was reversed. In 2% O₂ a step increase from 200 to 1000 ppm significantly decreased g(m) by 26-40% in all three species, whereas following a step decrease from 1000 to 200 ppm, the 26-38% increase in g(m) was not statistically significant. The response of g(m) to CO₂ was less in 21% O₂. Comparing wild type against the ost1 revealed that mesophyll and stomatal conductance varied independently in response to CO₂. We discuss the effects of isotope fractionation factors on estimating g(m) .

Association between water and carbon dioxide transport in leaf plasma membranes: assessing the role of aquaporins

Publisher: Wiley

Date: 14-10-2016

DOI: 10.1111/PCE.12830

Abstract: The role of some aquaporins as CO

Biochemical model of C ₃ photosynthesis applied to wheat at different temperatures

Publisher: Wiley

Date: 02-06-2017

DOI: 10.1111/PCE.12953

Abstract: We examined the effects of leaf temperature on the estimation of maximal Rubisco capacity (V

Phosphorus acquisition from soil by white lupin (Lupinus albus L.) and soybean (Glycine max L.), species with contrasting root development

Publisher: Springer Science and Business Media LLC

Date: 2003

DOI: 10.1023/A:1022332700686

The cyanobacterial CCM as a source of genes for improving photosynthetic CO2 fixation in crop species

Publisher: Oxford University Press (OUP)

Date: 10-2013

DOI: 10.1093/JXB/ERS257

Abstract: Crop yields need to nearly double over the next 35 years to keep pace with projected population growth. Improving photosynthesis, via a range of genetic engineering strategies, has been identified as a promising target for crop improvement with regard to increased photosynthetic yield and better water-use efficiency (WUE). One approach is based on integrating components of the highly efficient CO(2)-concentrating mechanism (CCM) present in cyanobacteria (blue-green algae) into the chloroplasts of key C(3) crop plants, particularly wheat and rice. Four progressive phases towards engineering components of the cyanobacterial CCM into C(3) species can be envisaged. The first phase (1a), and simplest, is to consider the transplantation of cyanobacterial bicarbonate transporters to C(3) chloroplasts, by host genomic expression and chloroplast targeting, to raise CO(2) levels in the chloroplast and provide a significant improvement in photosynthetic performance. Mathematical modelling indicates that improvements in photosynthesis as high as 28% could be achieved by introducing both of the single-gene, cyanobacterial bicarbonate transporters, known as BicA and SbtA, into C(3) plant chloroplasts. Part of the first phase (1b) includes the more challenging integration of a functional cyanobacterial carboxysome into the chloroplast by chloroplast genome transformation. The later three phases would be progressively more elaborate, taking longer to engineer other functional components of the cyanobacterial CCM into the chloroplast, and targeting photosynthetic and WUE efficiencies typical of C(4) photosynthesis. These later stages would include the addition of NDH-1-type CO(2) pumps and suppression of carbonic anhydrase and C(3) Rubisco in the chloroplast stroma. We include a score card for assessing the success of physiological modifications gained in phase 1a.

A cross‐scale analysis to understand and quantify the effects of photosynthetic enhancement on crop growth and yield across environments

Publisher: Wiley

Date: 20-10-2023

DOI: 10.1111/PCE.14453

Abstract: Photosynthetic manipulation provides new opportunities for enhancing crop yield. However, understanding and quantifying the importance of in idual and multiple manipulations on the seasonal biomass growth and yield performance of target crops across variable production environments is limited. Using a state‐of‐the‐art cross‐scale model in the APSIM platform we predicted the impact of altering photosynthesis on the enzyme‐limited ( A c ) and electron transport‐limited ( A j ) rates, seasonal dynamics in canopy photosynthesis, biomass growth, and yield formation via large multiyear‐by‐location crop growth simulations. A broad list of promising strategies to improve photosynthesis for C 3 wheat and C 4 sorghum were simulated. In the top decile of seasonal outcomes, yield gains were predicted to be modest, ranging between 0% and 8%, depending on the manipulation and crop type. We report how photosynthetic enhancement can affect the timing and severity of water and nitrogen stress on the growing crop, resulting in nonintuitive seasonal crop dynamics and yield outcomes. We predicted that strategies enhancing A c alone generate more consistent but smaller yield gains across all water and nitrogen environments, A j enhancement alone generates larger gains but is undesirable in more marginal environments. Large increases in both A c and A j generate the highest gains across all environments. Yield outcomes of the tested manipulation strategies were predicted and compared for realistic Australian wheat and sorghum production. This study uniquely unpacks complex cross‐scale interactions between photosynthesis and seasonal crop dynamics and improves understanding and quantification of the potential impact of photosynthesis traits (or lack of it) for crop improvement research.

Phosphorus availability and elevated CO₂ affect biological nitrogen fixation and nutrient fluxes in a clover‐dominated sward

Publisher: Wiley

Date: 17-10-2005

DOI: 10.1111/J.1469-8137.2005.01568.X

Abstract: The response of biological nitrogen fixation (BNF) to elevated CO(2) was examined in white clover (Trifolium repens)-dominated swards under both high and low phosphorus availability. Mixed swards of clover and buffalo grass (Stenotaphrum secundatum) were grown for 15 months in 0.2 m2 sand-filled mesocosms under two CO2 treatments (ambient and twice ambient) and three nutrient treatments [no N, and either low or high P (5 or 134 kg P ha(-1)) the third nutrient treatment was supplied with high P and N (240 kg N ha(-1))]. Under ambient CO2, high P increased BNF from 410 to 900 kg ha(-1). Elevated CO2 further increased BNF to 1180 kg ha(-1) with high P, but there was no effect of CO2 on BNF with low P. Allocation of N belowground increased by approx. 50% under elevated CO2 irrespective of supplied P. The results suggest that where soil P availability is low, elevated CO2 will not increase BNF, and pasture quality could decrease because of a reduction in aboveground N.

Exploring the Plant Aquaporin Solute Transport Network: Functional characterisation ofNicotiana tabacumPIP, TIP and NIP isoforms

Publisher: Cold Spring Harbor Laboratory

Date: 28-03-2021

DOI: 10.1101/2021.03.26.437249

Abstract: Aquaporins (AQPs) are multifunctional membrane proteins which have greatly ersified in number and function in the plant Kingdom. In plants, AQPs have evolved to comprise a dynamic solute transport network occurring in all tissues and facilitating transport of water and vital solutes across various cellular membranes. Plant AQPs are involved in a multitude of plant physiological processes, however a better understanding is required of AQP structure-function relationships, multifunctionality and cell membrane localisation in order to begin to describe putative functional roles for the numerous plant AQP gene isoforms. Using an integrated approach, we characterised nine erse Nicotiana tabacum (tobacco) aquaporins, spanning the 3 largest AQP subfamilies (PIP, TIP, and NIP) and with varied gene expression profiles. High-throughput yeast-based functional screens identified novel candidates for water, hydrogen peroxide (H 2 O 2 ), boric acid (BA) and urea transport across the 3 AQP subfamilies. Using GFP translational fusions, AQPs observed in planta were localised to the plasma membrane, tonoplast and endoplasmic reticulum. AlphaFold protein models illustrated differences in pore shape and size across subfamilies. Our analysis supports the importance of functional data for deciphering unknown AQP structure-function relationships and uncovering novel candidates for in planta solute transport.

Physiological and structural tradeoffs underlying the leaf economics spectrum

Publisher: Wiley

Date: 10-03-2017

DOI: 10.1111/NPH.14496

Abstract: The leaf economics spectrum ( LES ) represents a suite of intercorrelated leaf traits concerning construction costs per unit leaf area, nutrient concentrations, and rates of carbon fixation and tissue turnover. Although broad trade‐offs among leaf structural and physiological traits have been demonstrated, we still do not have a comprehensive view of the fundamental constraints underlying the LES trade‐offs. Here, we investigated physiological and structural mechanisms underpinning the LES by analysing a novel data compilation incorporating rarely considered traits such as the dry mass fraction in cell walls, nitrogen allocation, mesophyll CO 2 diffusion and associated anatomical traits for hundreds of species covering major growth forms. The analysis demonstrates that cell wall constituents are major components of leaf dry mass (18–70%), especially in leaves with high leaf mass per unit area ( LMA ) and long lifespan. A greater fraction of leaf mass in cell walls is typically associated with a lower fraction of leaf nitrogen (N) invested in photosynthetic proteins and lower within‐leaf CO 2 diffusion rates, as a result of thicker mesophyll cell walls. The costs associated with greater investments in cell walls underpin the LES : long leaf lifespans are achieved via higher LMA and in turn by higher cell wall mass fraction, but this inevitably reduces the efficiency of photosynthesis.

Functional Analysis of Corn Husk Photosynthesis

Publisher: Oxford University Press (OUP)

Date: 21-04-2011

DOI: 10.1104/PP.111.176495

Abstract: The husk surrounding the ear of corn/maize (Zea mays) has widely spaced veins with a number of interveinal mesophyll (M) cells and has been described as operating a partial C3 photosynthetic pathway, in contrast to its leaves, which use the C4 photosynthetic pathway. Here, we characterized photosynthesis in maize husk and leaf by measuring combined gas exchange and carbon isotope discrimination, the oxygen dependence of the CO2 compensation point, and photosynthetic enzyme activity and localization together with anatomy. The CO2 assimilation rate in the husk was less than that in the leaves and did not saturate at high CO2, indicating CO2 diffusion limitations. However, maximal photosynthetic rates were similar between the leaf and husk when expressed on a chlorophyll basis. The CO2 compensation points of the husk were high compared with the leaf but did not vary with oxygen concentration. This and the low carbon isotope discrimination measured concurrently with gas exchange in the husk and leaf suggested C4-like photosynthesis in the husk. However, both Rubisco activity and the ratio of phosphoenolpyruvate carboxylase to Rubisco activity were reduced in the husk. Immunolocalization studies showed that phosphoenolpyruvate carboxylase is specifically localized in the layer of M cells surrounding the bundle sheath cells, while Rubisco and glycine decarboxylase were enriched in bundle sheath cells but also present in M cells. We conclude that maize husk operates C4 photosynthesis dispersed around the widely spaced veins (analogous to leaves) in a diffusion-limited manner due to low M surface area exposed to intercellular air space, with the functional role of Rubisco and glycine decarboxylase in distant M yet to be explained.

Permeability profiling of all 13 Arabidopsis PIP aquaporins using a high throughput yeast approach

Publisher: Cold Spring Harbor Laboratory

Date: 10-05-2021

DOI: 10.1101/2021.05.09.443061

Abstract: Plant aquaporins have many more functions than just transporting water. Within the ersity of plant aquaporins are isoforms capable of transporting signaling molecules, nutrients, metalloids and gases. It is established that aquaporin substrate discrimination depends on combinations of factors such as solute size, pore size and polarity, and post-translational protein modifications. But our understanding of the relationships between variation in aquaporin structures and the implications for permeability is limited. High-throughput yeast-based assays were developed to assess erse substrate permeabilities to water, H 2 O 2 , boric acid, urea and Na + . All 13 plasma membrane intrinsic proteins (PIPs) from Arabidopsis (AtPIPs) were permeable to both water and H 2 O 2 , although their effectiveness varied, and none were permeable to urea. AtPIP2 isoforms were more permeable to water than AtPIP1s, while AtPIP1s were more efficient at transporting H 2 O 2 with AtPIP1 and AtPIP1 being the most permeable. Among the AtPIP2s, AtPIP2 and AtPIP2 were also permeable to boric acid and Na + . Linking AtPIP substrate profiles with phylogenetics and gene expression data enabled us to align substrate preferences with known biological roles of AtPIPs and importantly guide towards unidentified roles hidden by functional redundancy at key developmental stages and within tissue types. This analysis positions us to more strategically test in planta physiological roles of AtPIPs in order to unravel their complex contributions to the transport of important substrates, and secondly, to resolve links between aquaporin protein structure, substrate discrimination, and transport efficiency. Yeast based high throughput assays were developed to assess the permeability of each Arabidopsis PIP aquaporin isoform to water, H 2 O 2 , boric acid, urea and sodium.

Changes in Nutritional Value of Cyanogenic Trifolium repens Grown at Elevated Atmospheric CO2

Publisher: Springer Science and Business Media LLC

Date: 04-2009

DOI: 10.1007/S10886-009-9617-5

Abstract: Global food security in a changing climate depends on both the nutritive value of staple crops as well as their yields. Here, we examined the direct effect of atmospheric carbon dioxide on the toxicity of the important pasture crop, Trifolium repens L. (clover). Shoots of T. repens contain cyanogenic glycosides that break down to release toxic hydrogen cyanide when damaged. The ability of animals to tolerate cyanogenic compounds is dependent, in part, on their overall protein intake. We grew T. repens communities at ambient and approximately twice-ambient CO(2) in a controlled environment greenhouse experiment. We found that the ratio of total cyanogenic glycosides to total protein ratio was nearly two times higher in leaves of T. repens grown at elevated CO(2). This study highlights the importance of assessing the nutritive value of this and other plants in response to rising CO(2) so that steps can be taken to address any adverse consequences for herbivores.

Nitrogen in cell walls of sclerophyllous leaves accounts for little of the variation in photosynthetic nitrogen-use efficiency

Publisher: Wiley

Date: 27-01-2009

DOI: 10.1111/J.1365-3040.2008.01918.X

Abstract: Photosynthetic rate per unit nitrogen generally declines as leaf mass per unit area (LMA) increases. To determine how much of this decline was associated with allocating a greater proportion of leaf nitrogen into cell wall material, we compared two groups of plants. The first group consisted of two species from each of eight genera, all of which were perennial evergreens growing in the Australian National Botanic Gardens (ANBG). The second group consisted of seven Eucalyptus species growing in a greenhouse. The percentage of leaf biomass in cell walls was independent of variation in LMA within any genus, but varied from 25 to 65% between genera. The nitrogen concentration of cell wall material was 0.4 times leaf nitrogen concentration for all species apart from Eucalyptus, which was 0.6 times leaf nitrogen concentration. Between 10 and 30% of leaf nitrogen was recovered in the cell wall fraction, but this was independent of LMA. No trade-off was observed between nitrogen associated with cell walls and the nitrogen allocated to ribulose 1.5-bisphosphate carboxylase/oxygenase (Rubisco). Variation in photosynthetic rate per unit nitrogen could not be explained by variation in cell wall nitrogen.

Hyperspectral reflectance as a tool to measure biochemical and physiological traits in wheat

Publisher: Oxford University Press (OUP)

Date: 22-12-2017

DOI: 10.1093/JXB/ERX421

Stomatal crypts may facilitate diffusion of CO2 to adaxial mesophyll cells in thick sclerophylls

Publisher: Wiley

Date: 08-10-2009

DOI: 10.1111/J.1365-3040.2009.02024.X

Abstract: In some plants, stomata are exclusively located in epidermal depressions called crypts. It has been argued that crypts function to reduce transpiration however, the occurrence of crypts in species from both arid and wet environments suggests that crypts may play another role. The genus Banksia was chosen to examine quantitative relationships between crypt morphology and leaf structural and physiological traits to gain insight into the functional significance of crypts. Crypt resistance to water vapour and CO(2) diffusion was calculated by treating crypts as an additional boundary layer partially covering one leaf surface. Gas exchange measurements of polypropylene meshes confirmed the validity of this approach. Stomatal resistance was calculated as leaf resistance minus calculated crypt resistance. Stomata contributed significantly more than crypts to leaf resistance. Crypt depth increased and accounted for an increasing proportion of leaf resistance in species with greater leaf thickness and leaf dry mass per area. All Banksia species examined with leaves thicker than 0.6 mm had their stomata in deep crypts. We propose that crypts function to facilitate CO(2) diffusion from the abaxial surface to adaxial palisade cells in thick leaves. This and other possible functions of stomatal crypts, including a role in water use, are discussed.

Influence of leaf dry mass per area, CO2, and irradiance on mesophyll conductance in sclerophylls

Publisher: Oxford University Press (OUP)

Date: 13-03-2009

DOI: 10.1093/JXB/ERP021

Abstract: Leaf photosynthesis (A) is limited by mesophyll conductance (g(m)), which is influenced by both leaf structure and the environment. Previous studies have indicated that the upper bound for g(m) declines as leaf dry mass per area (LMA, an indicator of leaf structure) increases, extrapolating to zero at a LMA of about 240 g m(-2). No data exist on g(m) and its response to the environment for species with LMA values higher than 220 g m(-2). In this study, laboratory measurements of leaf gas exchange and in vivo chlorophyll a fluorescence were used concurrently to derive estimates of g(m) in seven species of the Australian sclerophyllous genus Banksia covering a wide range of LMA (130-480 g m(-2)). Irradiance and CO(2) were varied during those measurements to gauge the extent of environmental effects on g(m). A significant decrease of g(m) with increasing LMA was found. g(m) declined by 35-60% in response to increasing atmospheric CO(2) concentrations at high irradiance, with a more variable response (0-60%) observed at low irradiance, where g(m) was, on average, 22% lower than at high irradiance at ambient CO(2) concentrations. Despite considerable variation in A and LMA between the Banksia species, the CO(2) concentrations in the intercellular air spaces (C(i), 262+/-5 micromol mol(-1)) and in the chloroplasts (C(c), 127+/-4 micromol mol(-1)) were remarkably stable.

Exploiting transplastomically modified Rubisco to rapidly measure natural diversity in its carbon isotope discrimination using tuneable diode laser spectroscopy

Publisher: Oxford University Press (OUP)

Date: 31-03-2014

DOI: 10.1093/JXB/ERU036

A simple new equation for the reversible temperature dependence of photosynthetic electron transport: a study on soybean leaf

Publisher: CSIRO Publishing

Date: 2004

DOI: 10.1071/FP03250

Abstract: The temperature response of Jmax, the irradiance-saturated potential rate of photosynthetic electron transport in the absence of Rubisco limitation, has usually been modelled by a complicated, modified Arrhenius type of equation. Light saturation can be difficult to achieve and reduces the precision of fluorescence measurements. Consequently, we calculated the rate of electron transport at 1200 μmol photosynthetically active radiation (PAR) quanta m–2 s–1 from chlorophyll fluorescence measurements on intact soybean leaves [Glycine max (L.) Merr] as temperature increased from 15 to 43°C with 1250 μmol mol–1 ambient [CO2]. Electron transport rate was maximal around 37°C and the decline in rate following further increases in leaf temperature to 43°C was found to be completely reversible immediately upon return to lower temperatures. We report a convenient, new equation for the temperature dependence of the rate of electron transport under high irradiance:...

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.

Photosynthetic nitrogen-use efficiency of species that differ inherently in specific leaf area

Publisher: Springer Science and Business Media LLC

Date: 10-08-1998

DOI: 10.1007/S004420050560

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.

The Solar Action Spectrum of Photosystem II Damage    

Publisher: Oxford University Press (OUP)

Date: 11-05-2010

DOI: 10.1104/PP.110.155747

Abstract: The production of oxygen and the supply of energy for life on earth rely on the process of photosynthesis using sunlight. Paradoxically, sunlight damages the photosynthetic machinery, primarily photosystem II (PSII), leading to photoinhibition and loss of plant performance. However, there is uncertainty about which wavelengths are most damaging to PSII under sunlight. In this work we examined this in a simple experiment where Arabidopsis (Arabidopsis thaliana) leaves were exposed to different wavelengths of sunlight by dispersing the solar radiation across the surface of the leaf via a prism. To isolate only the process of photodamage, the repair of photodamaged PSII was inhibited by infiltration of chlor henicol into the exposed leaves. The extent of photodamage was then measured as the decrease in the maximum quantum yield of PSII using an imaging pulse litude modulation fluorometer. Under the experimental light conditions, photodamage to PSII occurred most strongly in regions exposed to ultraviolet (UV) or yellow light. The extent of UV photodamage under incident sunlight would be greater than we observed when one corrects for the optical efficiency of our system. Our results suggest that photodamage to PSII under sunlight is primarily associated with UV rather than photosynthetically active light wavelengths.

A unique web resource for physiology, ecology and the environmental sciences: PrometheusWiki

Publisher: CSIRO Publishing

Date: 2010

DOI: 10.1071/FP10097

Abstract: PROtocols, METHods, Explanations and Updated Standards Wiki (PrometheusWiki, www.publish.csiro.au rometheuswiki/) is a new open access, fully searchable web resource that contains protocols and methods for plant physiology, ecology and environmental sciences. Contributions can be uploaded by anyone in the community, with attributed authorship, and are open for wiki-style comment. This resource allows the gathering in one place of methods, links to published methods and detailed protocols used by leading laboratories around the world, with annotation. As a web resource, PrometheusWiki is continually evolving and updatable, easily and rapidly searchable and highly accessible. It will also enhance communication, allowing multimedia description of protocols and techniques, with spreadsheet tools, slide shows and video files easily integrated into the text. This resource is anticipated to lead to strong benefits in standardising methods, improving access to training for students and professionals, promoting collaborations and expanding the cutting edge of research.

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.

Photosynthesis at an extreme end of the leaf trait spectrum: how does it relate to high leaf dry mass per area and associated structural parameters?

Publisher: Oxford University Press (OUP)

Date: 19-05-2010

DOI: 10.1093/JXB/ERQ128

Global variability in leaf respiration in relation to climate, plant functional types and leaf traits

Publisher: Wiley

Date: 05-08-0008

DOI: 10.1111/NPH.13253

Abstract: Leaf dark respiration ( R dark ) is an important yet poorly quantified component of the global carbon cycle. Given this, we analyzed a new global database of R dark and associated leaf traits. Data for 899 species were compiled from 100 sites (from the Arctic to the tropics). Several woody and nonwoody plant functional types (PFTs) were represented. Mixed‐effects models were used to disentangle sources of variation in R dark . Area‐based R dark at the prevailing average daily growth temperature ( T ) of each site increased only twofold from the Arctic to the tropics, despite a 20°C increase in growing T (8–28°C). By contrast, R dark at a standard T (25°C, R dark 25 ) was threefold higher in the Arctic than in the tropics, and twofold higher at arid than at mesic sites. Species and PFTs at cold sites exhibited higher R dark 25 at a given photosynthetic capacity ( V cmax 25 ) or leaf nitrogen concentration ([N]) than species at warmer sites. R dark 25 values at any given V cmax 25 or [N] were higher in herbs than in woody plants. The results highlight variation in R dark among species and across global gradients in T and aridity. In addition to their ecological significance, the results provide a framework for improving representation of R dark in terrestrial biosphere models (TBMs) and associated land‐surface components of Earth system models (ESMs).

A consensus on the Aquaporin Gene Family in the Allotetraploid Plant, Nicotiana tabacum

Publisher: Wiley

Date: 05-2021

DOI: 10.1002/PLD3.321

Effects of water availability, nitrogen supply and atmospheric CO2 concentrations on plant nitrogen natural abundance values

Publisher: CSIRO Publishing

Date: 2006

DOI: 10.1071/FP05188

Abstract: The relative effects of soil N, water supply and elevated atmospheric CO2 on foliar δ15N values were examined. Phalaris arundinacea L. (Holdfast) and Physalis peruviana L. (Cape Gooseberry) were grown for 80 d with three water availability treatments, two atmospheric CO2 concentrations and four N supply rates. Elevated CO2 increased total plant biomass and N for each treatment and decreased allocation to roots, leaf N concentrations and stomatal conductance. Leaves had less negative leaf δ13C values under low water supply associated with decreased stomatal conductance and increased leaf N concentration, which decreased the ratio of intercellular to ambient CO2 concentration. The δ15N value of the supplied nitrate (4.15‰) was similar to the value for Phalaris leaves (4.11‰), but Cape Gooseberry leaves were enriched (6.52‰). The effects of elevated CO2 on leaf δ15N values were small, with Phalaris showing no significant change, while Cape Gooseberry showed a significant (P 0.05) decline of 0.42 ‰. Variation in δ15N values was unrelated to stomatal conductance, transpiration, differential use of N forms or denitrification. Plants with low foliar N concentrations tended to be depleted in 15N. We suggest that changes in N allocation alter foliar δ15N values under different CO2 and water treatments.

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

Publisher: Oxford University Press (OUP)

Date: 09-09-2014

DOI: 10.1093/JXB/ERU367

Mesophyll conductance does not contribute to greater photosynthetic rate per unit nitrogen in temperate compared with tropical evergreen wet-forest tree leaves

Publisher: Wiley

Date: 13-02-2018

DOI: 10.1111/NPH.15031

Abstract: Globally, trees originating from high-rainfall tropical regions typically exhibit lower rates of light-saturated net CO

The nitrogen cost of photosynthesis

Publisher: Oxford University Press (OUP)

Date: 23-10-2018

DOI: 10.1093/JXB/ERY366

Abstract: Global food security depends on three main cereal crops (wheat, rice and maize) achieving and maintaining high yields, as well as increasing their future yields. Fundamental to the production of this biomass is photosynthesis. The process of photosynthesis involves a large number of proteins that together account for the majority of the nitrogen in leaves. As large amounts of nitrogen are removed in the harvested grain, this needs to be replaced either from synthetic fertilizer or biological nitrogen fixation. Knowledge about photosynthetic properties of leaves in natural ecosystems is also important, particularly when we consider the potential impacts of climate change. While the relationship between nitrogen and photosynthetic capacity of a leaf differs between species, leaf nitrogen content provides a useful way to incorporate photosynthesis into models of ecosystems and the terrestrial biosphere. This review provides a generalized nitrogen budget for a C3 leaf cell and discusses the potential for improving photosynthesis from a nitrogen perspective.

The importance of species-specific and temperature-sensitive parameterisation of A / C i models: a case study using cotton ( Gossypium hirsutum L.) and the automated ‘OptiFitACi’ R-package.

Publisher: Authorea, Inc.

Date: 07-08-2023

DOI: 10.22541/AU.169140993.39140230/V1

Abstract: Leaf gas exchange measurements provide an important tool for inferring a plant’s photosynthetic biochemistry. In most cases, the responses of photosynthetic CO assimilation to variable intercellular CO concentrations ( A / C response curves) are used to model the maximum rate of carboxylation by ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco, V ) and the rate of electron transport at a given photosynthetically active radiation (PAR J ). The standard Farquhar-Von Caemmerer-Berry model is typically used with default parameters of Rubisco kinetic values and mesophyll conductance to CO ( g ) derived from tobacco that impairs analytical reliability across species. To study this, here we measured the temperature responses of key in vitro Rubisco catalytic properties and g in cotton ( Gossypium hirsutum cv. Sicot 71) and derived V and J ( J at 2000 µmol m s PAR) from cotton A / C curves incrementally measured at 15°C to 40°C using cotton and tobacco parameters with our new automated fitting R package ‘OptiFitACi’. When applied to cotton, the tobacco parameters produced unrealistic J : V ratio of at 25°C, two- to three-fold higher estimates of V , approximately 50% higher estimates of J and more variable estimates of V and J , compared to model parameterisation with cotton-derived values. We determined that errors arise when using a g of 0.23 mol m s bar or below and Rubisco CO -affinities under ambient O ( K ) outside 461 µbar to 627 µbar to model A / C responses in cotton. We show how the multi- A / C modelling capabilities of ‘OptiFitACi’ serves as a robust, user-friendly extension of ‘plantecophys’ by providing simplified temperature-sensitivity and species-specificity parameterisation capabilities to enable higher accuracy estimates of V and J .

Enhancing crop yields through improvements in the efficiency of photosynthesis and respiration

Publisher: Wiley

Date: 17-11-2023

DOI: 10.1111/NPH.18545

Abstract: The rate with which crop yields per hectare increase each year is plateauing at the same time that human population growth and other factors increase food demand. Increasing yield potential () of crops is vital to address these challenges. In this review, we explore a component of that has yet to be optimised – that being improvements in the efficiency with which light energy is converted into biomass () via modifications to CO 2 fixed per unit quantum of light ( α ), efficiency of respiratory ATP production () and efficiency of ATP use (). For α , targets include changes in photoprotective machinery, ribulose bisphosphate carboxylase/oxygenase kinetics and photorespiratory pathways. There is also potential for to be increased via targeted changes to the expression of the alternative oxidase and mitochondrial uncoupling pathways. Similarly, there are possibilities to improve via changes to the ATP costs of phloem loading, nutrient uptake, futile cycles and/or protein/membrane turnover. Recently developed high‐throughput measurements of respiration can serve as a proxy for the cumulative energy cost of these processes. There are thus exciting opportunities to use our growing knowledge of factors influencing the efficiency of photosynthesis and respiration to create a step‐change in yield potential of globally important crops.

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.

Effect of leaf temperature on the estimation of photosynthetic and other traits of wheat leaves from hyperspectral reflectance

Publisher: Oxford University Press (OUP)

Date: 30-11-2020

DOI: 10.1093/JXB/ERAA514

Abstract: A growing number of leaf traits can be estimated from hyperspectral reflectance data. These include structural and compositional traits, such as leaf mass per area (LMA) and nitrogen and chlorophyll content, but also physiological traits such a Rubisco carboxylation activity, electron transport rate, and respiration rate. Since physiological traits vary with leaf temperature, how does this impact on predictions made from reflectance measurements? We investigated this with two wheat varieties, by repeatedly measuring each leaf through a sequence of temperatures imposed by varying the air temperature in a growth room. Leaf temperatures ranging from 20 °C to 35 °C did not alter the estimated Rubisco capacity normalized to 25 °C (Vcmax25), or chlorophyll or nitrogen contents per unit leaf area. Models estimating LMA and Vcmax25/N were both slightly influenced by leaf temperature: estimated LMA increased by 0.27% °C–1 and Vcmax25/N increased by 0.46% °C–1. A model estimating Rubisco activity closely followed variation associated with leaf temperature. Reflectance spectra change with leaf temperature and therefore contain a temperature signal.

Leaf mesophyll diffusion conductance in 35 Australian sclerophylls covering a broad range of foliage structural and physiological variation

Publisher: Oxford University Press (OUP)

Date: 02-03-2009

DOI: 10.1093/JXB/ERP045

Abstract: Foliage structure, chemistry, photosynthetic potentials (V(cmax) and J(max)), and mesophyll diffusion conductance (g(m)) were quantified for 35 broad-leaved species from four sites with contrasting rainfall and soil fertility in eastern Australia. The aim of the study was to estimate the extent to which g(m) and related leaf properties limited photosynthesis (A), focusing on highly sclerophyllous species typical of the 'slow-return' end of the leaf economics spectrum. Leaf dry mass per unit area (M(A)) varied approximately 5-fold, leaf life span (L(L)) and N (N(M)) and P (P(M)) contents per dry mass approximately 8-fold, and various characteristics of foliage photosynthetic machinery 6- to 12-fold across the data set. As is characteristic of the 'leaf economics spectrum', more robust leaves with greater M(A) and longevity were associated with lower nutrient contents and lower foliage photosynthetic potentials. g(m) was positively correlated with V(cmax) and J(max), and these correlations were stronger on a mass basis. Only g(m)/mass was negatively associated with M(A). CO(2) drawdown from substomatal cavities to chloroplasts (C(i)-C(C)) characterizing mesophyll CO(2) diffusion limitations was larger in leaves with greater M(A), lower g(m)/mass, and lower photosynthetic potentials. Relative limitation of A due to finite mesophyll diffusion conductance, i.e. 1-A(infinite g(m))/A(actual g(m)), was always >0.2 and up to 0.5 in leaves with most robust leaf structure, demonstrating the profound effect of finite g(m) on realized photosynthesis rates. Data from different sites were overlapping in bivariate relationships, and the variability of average values between the sites was less than among the species within the sites. Nevertheless, photosynthesis was more strongly limited by g(m) in low rain/high nutrient and high rain/low nutrient sites that supported vegetation with more sclerophyllous foliage. These data collectively highlight a strong relationship between leaf structure and g(m), and demonstrate that realized photosynthesis rates are strongly limited by g(m) in this highly sclerophyllous flora.

From green to gold: agricultural revolution for food security

Publisher: Oxford University Press (OUP)

Date: 06-04-2020

DOI: 10.1093/JXB/ERAA110

High-resolution temperature responses of leaf respiration in snow gum (Eucalyptus pauciflora) reveal high-temperature limits to respiratory function

Publisher: Wiley

Date: 24-01-2013

DOI: 10.1111/PCE.12057

Abstract: We tested whether snow gum (Eucalyptus pauciflora) trees growing in thermally contrasting environments exhibit generalizable temperature (T) response functions of leaf respiration (R) and fluorescence (Fo). Measurements were made on pot-grown saplings and field-grown trees (growing between 1380 and 2110 m a.s.l.). Using a continuous, high-resolution protocol, we quantified T response curves of R and Fo--these data were used to identify an algorithm for modelling R-T curves at subcritical T's and establish variations in heat tolerance. For the latter, we quantified Tmax [T where R is maximal] and Tcrit [T where Fo rises rapidly]. Tmax ranged from 51 to 57 °C, varying with season (e.g. winter summer). Tcrit ranged from 41 to 49 °C in summer and from 58 to 63 °C in winter. Thus, surprisingly, leaf energy metabolism was more heat-tolerant in trees experiencing ice-encasement in winter than warmer conditions in summer. A polynomial model fitted to log-transformed R data provided the best description of the T-sensitivity of R (between 10 and 45 °C) using these model fits, we found that the negative slope of the Q10 -T relationship was greater in winter than in summer. Collectively, our results (1) highlight high-T limits of energy metabolism in E. pauciflora and (2) provide a framework for improving representation of T-responses of leaf R in predictive models.

Strong thermal acclimation of photosynthesis in tropical and temperate wet‐forest tree species: the importance of altered Rubisco content

Publisher: Wiley

Date: 03-01-2017

DOI: 10.1111/GCB.13566

Abstract: Understanding of the extent of acclimation of light-saturated net photosynthesis (A

AusTraits, a curated plant trait database for the Australian flora

Publisher: Springer Science and Business Media LLC

Date: 30-09-2021

DOI: 10.1038/S41597-021-01006-6

Abstract: We introduce the AusTraits database - a compilation of values of plant traits for taxa in the Australian flora (hereafter AusTraits). AusTraits synthesises data on 448 traits across 28,640 taxa from field c aigns, published literature, taxonomic monographs, and in idual taxon descriptions. Traits vary in scope from physiological measures of performance (e.g. photosynthetic gas exchange, water-use efficiency) to morphological attributes (e.g. leaf area, seed mass, plant height) which link to aspects of ecological variation. AusTraits contains curated and harmonised in idual- and species-level measurements coupled to, where available, contextual information on site properties and experimental conditions. This article provides information on version 3.0.2 of AusTraits which contains data for 997,808 trait-by-taxon combinations. We envision AusTraits as an ongoing collaborative initiative for easily archiving and sharing trait data, which also provides a template for other national or regional initiatives globally to fill persistent gaps in trait knowledge.

Predicting dark respiration rates of wheat leaves from hyperspectral reflectance

Publisher: Wiley

Date: 28-03-2019

DOI: 10.1111/PCE.13544

Abstract: Greater availability of leaf dark respiration (R

Cover Image

Publisher: Wiley

Date: 08-12-2022

DOI: 10.1111/PCE.14512

Estimating mesophyll conductance to CO2: methodology, potential errors, and recommendations

Publisher: Oxford University Press (OUP)

Date: 08-04-2009

DOI: 10.1093/JXB/ERP081

Abstract: The three most commonly used methods for estimating mesophyll conductance (g(m)) are described. They are based on gas exchange measurements either (i) by themselves (ii) in combination with chlorophyll fluorescence quenching analysis or (iii) in combination with discrimination against (13)CO(2). To obtain reliable estimates of g(m), the highest possible accuracy of gas exchange is required, particularly when using small leaf chambers. While there may be problems in achieving a high accuracy with leaf chambers that cl onto a leaf with gaskets, guidelines are provided for making necessary corrections that increase reliability. All methods also rely on models for the calculation of g(m) and are sensitive to variation in the values of the model parameters. The sensitivity to these factors and to measurement error is analysed and ways to obtain the most reliable g(m) values are discussed. Small leaf areas can best be measured using one of the fluorescence methods. When larger leaf areas can be measured in larger chambers, the online isotopic methods are preferred. Using the large CO(2) draw-down provided by big chambers, and the isotopic method, is particularly important when measuring leaves with high g(m) that have a small difference in [CO(2)] between the substomatal cavity and the site of carboxylation in the chloroplast (C(i)-C(c) gradient). However, equipment for the fluorescence methods is more easily accessible. Carbon isotope discrimination can also be measured in recently synthesized carbohydrates, which has its advantages under field conditions when large number of s les must be processed. The curve-fitting method that uses gas exchange measurements only is not preferred and should only be used when no alternative is available. Since all methods have their weaknesses, the use of two methods for the estimation of g(m), which are as independent as possible, is recommended.

Food security requires genetic advances to increase farm yields

Publisher: Springer Science and Business Media LLC

Date: 07-04-2010

DOI: 10.1038/464831D

Leaf‐level photosynthetic capacity in lowland Amazonian and high‐elevation Andean tropical moist forests of Peru

Publisher: Wiley

Date: 08-07-2016

DOI: 10.1111/NPH.14079

Abstract: We examined whether variations in photosynthetic capacity are linked to variations in the environment and/or associated leaf traits for tropical moist forests ( TMF s) in the Andes/western Amazon regions of Peru. We compared photosynthetic capacity (maximal rate of carboxylation of Rubisco ( V cmax ), and the maximum rate of electron transport ( J max )), leaf mass, nitrogen (N) and phosphorus (P) per unit leaf area ( M a , N a and P a , respectively), and chlorophyll from 210 species at 18 field sites along a 3300‐m elevation gradient. Western blots were used to quantify the abundance of the CO 2 ‐fixing enzyme Rubisco. Area‐ and N‐based rates of photosynthetic capacity at 25°C were higher in upland than lowland TMF s, underpinned by greater investment of N in photosynthesis in high‐elevation trees. Soil [P] and leaf P a were key explanatory factors for models of area‐based V cmax and J max but did not account for variations in photosynthetic N‐use efficiency. At any given N a and P a , the fraction of N allocated to photosynthesis was higher in upland than lowland species. For a small subset of lowland TMF trees examined, a substantial fraction of Rubisco was inactive. These results highlight the importance of soil‐ and leaf‐P in defining the photosynthetic capacity of TMF s, with variations in N allocation and Rubisco activation state further influencing photosynthetic rates and N‐use efficiency of these critically important forests.

Proteoid Roots. Physiology and Development

Publisher: Oxford University Press (OUP)

Date: 10-1999

DOI: 10.1104/PP.121.2.317

Mesophyll conductance is unaffected by expression of Arabidopsis PIP1 aquaporins in the plasmalemma of Nicotiana

Publisher: Oxford University Press (OUP)

Date: 20-02-2022

DOI: 10.1093/JXB/ERAC065

Abstract: In plants with C3 photosynthesis, increasing the diffusion conductance for CO2 from the substomatal cavity to chloroplast stroma (mesophyll conductance) can improve the efficiencies of both CO2 assimilation and photosynthetic water use. In the diffusion pathway from substomatal cavity to chloroplast stroma, the plasmalemma and chloroplast envelope membranes impose a considerable barrier to CO2 diffusion, limiting photosynthetic efficiency. In an attempt to improve membrane permeability to CO2, and increase photosynthesis in tobacco, we generated transgenic lines in Nicotiana tabacum L. cv Petite Havana carrying either the Arabidopsis PIP1 (AtPIP1 ) or PIP1 (AtPIP1 ) gene driven by the constitutive dual 2x35S CMV promoter. From a collection of independent T0 transgenics, two T2 lines from each gene were characterized, with western blots confirming increased total aquaporin protein abundance in the AtPIP1 tobacco lines. Transient expression of AtPIP1 -mGFP6 and AtPIP1 -mGFP6 fusions in Nicotiana benthamiana identified that both AtPIP1 and AtPIP1 localize to the plasmalemma. Despite achieving ectopic production and correct localization, gas exchange measurements combined with carbon isotope discrimination measurements detected no increase in mesophyll conductance or CO2 assimilation rate in the tobacco lines expressing AtPIP. We discuss the complexities associated with trying to enhance gm through modified aquaporin activity.

Stomatal, mesophyll conductance, and biochemical limitations to photosynthesis during induction

Publisher: Oxford University Press (OUP)

Date: 30-11-2020

DOI: 10.1093/PLPHYS/KIAA011

Abstract: The dynamics of leaf photosynthesis in fluctuating light affects carbon gain by plants. Mesophyll conductance (gm) limits CO2 assimilation rate (A) under the steady state, but the extent of this limitation under non-steady-state conditions is unknown. In the present study, we aimed to characterize the dynamics of gm and the limitations to A imposed by gas diffusional and biochemical processes under fluctuating light. The induction responses of A, stomatal conductance (gs), gm, and the maximum rate of RuBP carboxylation (Vcmax) or electron transport (J) were investigated in Arabidopsis (Arabidopsis thaliana (L.)) and tobacco (Nicotiana tabacum L.). We first characterized gm induction after a change from darkness to light. Each limitation to A imposed by gm, gs and Vcmax or J was significant during induction, indicating that gas diffusional and biochemical processes limit photosynthesis. Initially, gs imposed the greatest limitation to A, showing the slowest response under high light after long and short periods of darkness, assuming RuBP-carboxylation limitation. However, if RuBP-regeneration limitation was assumed, then J imposed the greatest limitation. gm did not vary much following short interruptions to light. The limitation to A imposed by gm was the smallest of all the limitations for most of the induction phase. This suggests that altering induction kinetics of mesophyll conductance would have little impact on A following a change in light. To enhance the carbon gain by plants under naturally dynamic light environments, attention should therefore be focused on faster stomatal opening or activation of electron transport.

Effects of reduced carbonic anhydrase activity on CO₂assimilation rates inSetaria viridis: a transgenic analysis

Publisher: Oxford University Press (OUP)

Date: 04-10-2016

DOI: 10.1093/JXB/ERW357

Temperature response of mesophyll conductance in cultivated and wild Oryza species with contrasting mesophyll cell wall thickness

Publisher: Wiley

Date: 22-08-2011

DOI: 10.1111/J.1365-3040.2011.02398.X

Abstract: A critical component of photosynthetic capacity is the conductance of CO(2) from intercellular airspaces to the sites of CO(2) fixation in the stroma of chloroplasts, termed mesophyll conductance (g(m)). Leaf anatomy has been identified as an important determinant of g(m). There are few studies of the temperature response of g(m) and none has examined the implications of leaf anatomy. Hence, we compared a cultivar of Oryza sativa with two wild Oryza relatives endemic to the hot northern savannah of Australia, namely Oryza meridionalis and Oryza australiensis. All three species had similar leaf anatomical properties, except that the wild relatives had significantly thicker mesophyll cell walls than O. sativa. Thicker mesophyll cell walls in the wild rice species are likely to have contributed to the reduction in g(m) , which was associated with a greater drawdown of CO(2) into chloroplasts (C(i) -C(c) ) compared with O. sativa. Mesophyll conductance increased at higher temperatures, whereas the rate of CO(2) assimilation was relatively stable between 20 and 40 °C. Consequently, C(i) -C(c) decreased for all three species as temperature increased.

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

Carbon dioxide and water transport through plant aquaporins

Publisher: Wiley

Date: 12-2016

DOI: 10.1111/PCE.12844

Abstract: Aquaporins are channel proteins that function to increase the permeability of biological membranes. In plants, aquaporins are encoded by multigene families that have undergone substantial ersification in land plants. The plasma membrane intrinsic proteins (PIPs) subfamily of aquaporins is of particular interest given their potential to improve plant water relations and photosynthesis. Flowering plants have between 7 and 28 PIP genes. Their expression varies with tissue and cell type, through development and in response to a variety of factors, contributing to the dynamic and tissue specific control of permeability. There are a growing number of PIPs shown to act as water channels, but those altering membrane permeability to CO

Growth of the C-4 dicot Flaveria bidentis: photosynthetic acclimation to low light through shifts in leaf anatomy and biochemistry

Publisher: Oxford University Press (OUP)

Date: 06-08-2010

DOI: 10.1093/JXB/ERQ226

Effect of leaf temperature on estimating physiological traits of wheat leaves from hyperspectral reflectance

Publisher: Cold Spring Harbor Laboratory

Date: 25-05-2020

DOI: 10.1101/2020.05.21.109652

Abstract: A growing number of leaf traits can be predicted from hyperspectral reflectance data. These include structural and compositional traits, such as leaf mass per area, nitrogen and chlorophyll content, but also physiological traits such a Rubisco carboxylation activity, electron transport rate and respiration rate. Since physiological traits vary with leaf temperature, how does this impact on predictions made from reflectance measurements? We investigated this with two wheat varieties, by repeatedly measuring each leaf through a sequence of temperatures imposed by varying the air temperature in a growth room. The function predicting Rubisco capacity normalised to 25 °C predicted the same value, regardless of leaf temperatures ranging from 20 to 35°C. Leaf temperature affected none of the predicted traits: V cmax25 , J, chlorophyll content, LMA, N content per unit leaf area or V cmax25 /N. However, as others have derived models to predict Rubisco activity that includes variation associated with leaf temperature, we discuss whether these functions may include a temperature signal within the reflectance spectra.

AusTraits – a curated plant trait database for the Australian flora

Publisher: Cold Spring Harbor Laboratory

Date: 07-01-2021

DOI: 10.1101/2021.01.04.425314

Abstract: We introduce the AusTraits database - a compilation of measurements of plant traits for taxa in the Australian flora (hereafter AusTraits). AusTraits synthesises data on 375 traits across 29230 taxa from field c aigns, published literature, taxonomic monographs, and in idual taxa descriptions. Traits vary in scope from physiological measures of performance (e.g. photosynthetic gas exchange, water-use efficiency) to morphological parameters (e.g. leaf area, seed mass, plant height) which link to aspects of ecological variation. AusTraits contains curated and harmonised in idual-, species- and genus-level observations coupled to, where available, contextual information on site properties. This data descriptor provides information on version 2.1.0 of AusTraits which contains data for 937243 trait-by-taxa combinations. We envision AusTraits as an ongoing collaborative initiative for easily archiving and sharing trait data to increase our collective understanding of the Australian flora.

Growth and nutritive value of cassava (Manihot esculenta Cranz.) are reduced when grown in elevated CO2

Publisher: Wiley

Date: 23-09-2009

DOI: 10.1111/J.1438-8677.2009.00238.X

Phenotypic variation in photosynthetic traits in wheat grown under field versus glasshouse conditions

Publisher: Oxford University Press (OUP)

Date: 10-03-2022

DOI: 10.1093/JXB/ERAC096

Abstract: Recognition of the untapped potential of photosynthesis to improve crop yields has spurred research to identify targets for breeding. The CO2-fixing enzyme Rubisco is characterized by a number of inefficiencies, and frequently limits carbon assimilation at the top of the canopy, representing a clear target for wheat improvement. Two bread wheat lines with similar genetic backgrounds and contrasting in vivo maximum carboxylation activity of Rubisco per unit leaf nitrogen (Vc,max,25/Narea) determined using high-throughput phenotyping methods were selected for detailed study from a panel of 80 spring wheat lines. Detailed phenotyping of photosynthetic traits in the two lines using glasshouse-grown plants showed no difference in Vc,max,25/Narea determined directly via in vivo and in vitro methods. Detailed phenotyping of glasshouse-grown plants of the 80 wheat lines also showed no correlation between photosynthetic traits measured via high-throughput phenotyping of field-grown plants. Our findings suggest that the complex interplay between traits determining crop productivity and the dynamic environments experienced by field-grown plants needs to be considered in designing strategies for effective wheat crop yield improvement when breeding for particular environments.

Water and temperature stress define the optimal flowering period for wheat in south-eastern Australia

Publisher: Elsevier BV

Date: 08-2017

DOI: 10.1016/J.FCR.2017.04.012

Trait correlation networks: a whole-plant perspective on the recently criticized leaf economic spectrum

Publisher: Wiley

Date: 07-10-2014

DOI: 10.1111/NPH.12547

Contrasting anatomical and biochemical controls on mesophyll conductance across plant functional types

Publisher: Wiley

Date: 02-08-2022

DOI: 10.1111/NPH.18363

Abstract: Mesophyll conductance ( g m ) limits photosynthesis by restricting CO 2 diffusion between the substomatal cavities and chloroplasts. Although it is known that g m is determined by both leaf anatomical and biochemical traits, their relative contribution across plant functional types (PFTs) is still unclear. We compiled a dataset of g m measurements and concomitant leaf traits in unstressed plants comprising 563 studies and 617 species from all major PFTs. We investigated to what extent g m limits photosynthesis across PFTs, how g m relates to structural, anatomical, biochemical, and physiological leaf properties, and whether these relationships differ among PFTs. We found that g m imposes a significant limitation to photosynthesis in all C 3 PFTs, ranging from 10–30% in most herbaceous annuals to 25–50% in woody evergreens. Anatomical leaf traits explained a significant proportion of the variation in g m ( R 2 0.3) in all PFTs except annual herbs, in which g m is more strongly related to biochemical factors associated with leaf nitrogen and potassium content. Our results underline the need to elucidate mechanisms underlying the global variability of g m . We emphasise the underestimated potential of g m for improving photosynthesis in crops and identify modifications in leaf biochemistry as the most promising pathway for increasing g m in these species.

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.

A comment on the quantitative significance of aerobic methane release by plants

Publisher: CSIRO Publishing

Date: 2006

DOI: 10.1071/FP06051

Abstract: A recent study by Keppler et al. (2006 Nature 439, 187–191) demonstrated CH4 emission from living and dead plant tissues under aerobic conditions. This work included some calculations to extrapolate the findings from the laboratory to the global scale and led various commentators to question the value of planting trees as a greenhouse mitigation option. The experimental work of Keppler et al. (2006) appears to be largely sound, although some concerns remain about the quantification of emission rates. However, whilst accepting their basic findings, we are critical of the method used for extrapolating results to a global scale. Using the same basic information, we present alternative calculations to estimate global aerobic plant CH4 emissions as 10–60 Mt CH4 year–1. This estimate is much smaller than the 62–236 Mt CH4 year–1 reported in the original study and can be more readily reconciled within the uncertainties in the established sources and sinks in the global CH4 budget. We also assessed their findings in terms of their possible relevance for planting trees as a greenhouse mitigation option. We conclude that consideration of aerobic CH4 emissions from plants would reduce the benefit of planting trees by between 0 and 4.4%. Hence, any offset from CH4 emission is small in comparison to the significant benefit from carbon sequestration. However, much critical information is still lacking about aerobic CH4 emission from plants. For ex le, we do not yet know the underlying mechanism for aerobic CH4 emission, how CH4 emissions change with light, temperature and the physiological state of leaves, whether emissions change over time under constant conditions, whether they are related to photosynthesis and how they relate to the chemical composition of biomass. Therefore, the present calculations must be seen as a preliminary attempt to assess the global significance from a basis of limited information and are likely to be revised as further information becomes available.

Does greater night‐time, rather than constant, warming alter growth of managed pasture under under ambient and elevated atmospheric CO₂?

Publisher: Wiley

Date: 13-02-2004

DOI: 10.1111/J.1469-8137.2004.01025.X

Rubisco deactivation and chloroplast electron transport rates co-limit photosynthesis above optimal leaf temperature in terrestrial plants

Publisher: Springer Science and Business Media LLC

Date: 17-05-2023

DOI: 10.1038/S41467-023-38496-4

Abstract: Net photosynthetic CO 2 assimilation rate ( A n ) decreases at leaf temperatures above a relatively mild optimum ( T opt ) in most higher plants. This decline is often attributed to reduced CO 2 conductance, increased CO 2 loss from photorespiration and respiration, reduced chloroplast electron transport rate ( J ), or deactivation of Ribulose-1,5-bisphosphate Carboxylase Oxygenase (Rubisco). However, it is unclear which of these factors can best predict species independent declines in A n at high temperature. We show that independent of species, and on a global scale, the observed decline in A n with rising temperatures can be effectively accounted for by Rubisco deactivation and declines in J . Our finding that A n declines with Rubisco deactivation and J supports a coordinated down-regulation of Rubisco and chloroplast electron transport rates to heat stress. We provide a model that, in the absence of CO 2 supply limitations, can predict the response of photosynthesis to short-term increases in leaf temperature.

Online CO2 and H2O oxygen isotope fractionation allows estimation of mesophyll conductance in C4 plants, and reveals that mesophyll conductance decreases as leaves age in both C4 and C3 plants

Publisher: Wiley

Date: 18-01-2016

DOI: 10.1111/NPH.13830

Abstract: Mesophyll conductance significantly, and variably, limits photosynthesis but we currently have no reliable method of measurement for C 4 plants. An online oxygen isotope technique was developed to allow quantification of mesophyll conductance in C 4 plants and to provide an alternative estimate in C 3 plants. The technique is compared to an established carbon isotope method in three C 3 species. Mesophyll conductance of C 4 species was similar to that in the C 3 species measured, and declined in both C 4 and C 3 species as leaves aged from fully expanded to senescing. In cotton leaves, simultaneous measurement of carbon and oxygen isotope discrimination allowed the partitioning of total conductance to the chloroplasts into cell wall and plasma membrane versus chloroplast membrane components, if CO 2 was assumed to be isotopically equilibrated with cytosolic water, and the partitioning remained stable with leaf age. The oxygen isotope technique allowed estimation of mesophyll conductance in C 4 plants and, when combined with well‐established carbon isotope techniques, may provide additional information on mesophyll conductance in C 3 plants.

Faster Rubisco is the key to superior nitrogen-use efficiency in NADP-malic enzyme relative to NAD-malic enzyme C4 grasses

Publisher: Oxford University Press (OUP)

Date: 02-2005

DOI: 10.1104/PP.104.054759

Abstract: In 27 C4 grasses grown under adequate or deficient nitrogen (N) supplies, N-use efficiency at the photosynthetic (assimilation rate per unit leaf N) and whole-plant (dry mass per total leaf N) level was greater in NADP-malic enzyme (ME) than NAD-ME species. This was due to lower N content in NADP-ME than NAD-ME leaves because neither assimilation rates nor plant dry mass differed significantly between the two C4 subtypes. Relative to NAD-ME, NADP-ME leaves had greater in vivo (assimilation rate per Rubisco catalytic sites) and in vitro Rubisco turnover rates (k cat 3.8 versus 5.7 s−1 at 25°C). The two parameters were linearly related. In 2 NAD-ME (Panicum miliaceum and Panicum coloratum) and 2 NADP-ME (Sorghum bicolor and Cenchrus ciliaris) grasses, 30% of leaf N was allocated to thylakoids and 5% to 9% to amino acids and nitrate. Soluble protein represented a smaller fraction of leaf N in NADP-ME (41%) than in NAD-ME (53%) leaves, of which Rubisco accounted for one-seventh. Soluble protein averaged 7 and 10 g (mmol chlorophyll)−1 in NADP-ME and NAD-ME leaves, respectively. The majority (65%) of leaf N and chlorophyll was found in the mesophyll of NADP-ME and bundle sheath of NAD-ME leaves. The mesophyll-bundle sheath distribution of functional thylakoid complexes (photosystems I and II and cytochrome f) varied among species, with a tendency to be mostly located in the mesophyll. In conclusion, superior N-use efficiency of NADP-ME relative to NAD-ME grasses was achieved with less leaf N, soluble protein, and Rubisco having a faster k cat.

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