Oula Ghannoum

High temperature acclimation of C-4 photosynthesis is linked to changes in photosynthetic biochemistry

Publisher: Wiley

Date: 06-11-2007

DOI: 10.1111/J.1365-3040.2006.01605.X

Abstract: With average global temperatures predicted to increase over the next century, it is important to understand the extent and mechanisms of C4 photosynthetic acclimation to modest increases in growth temperature. To this end, we compared the photosynthetic responses of two C4 grasses (Panicum coloratum and Cenchrus ciliaris) and one C4 dicot (Flaveria bidentis) to growth at moderate (25/20 degrees C, day/night) or high (35/30 degrees C, day/night) temperatures. In all three C4 species, CO2 assimilation rates (A) underwent significant thermal acclimation, such that when compared at growth temperatures, A increased less than what would be expected given the strong response of A to short-term changes in leaf temperature. Thermal photosynthetic acclimation was further manifested by an increase in the temperature optima of A, and a decrease in leaf nitrogen content and leaf mass per area in the high- relative to the moderate-temperature-grown plants. Reduced photosynthetic capacity at the higher growth temperature was underpinned by selective changes in photosynthetic components. Plants grown at the higher temperature had lower amounts of ribulose-1,5-bisphosphate carboxylase/oxygenase and cytochrome f and activity of carbonic anhydrase. The activities of photosystem II (PSII) and phosphoenolpyruvate carboxylase were not affected by growth temperature. Chlorophyll fluorescence measurements of F. bidentis showed a corresponding decrease in the quantum yield of PSII (phi(PSII)) and an increase in non-photochemical quenching (phi(NPQ)). It is concluded that through these biochemical changes, C4 plants maintain the balance between the various photosynthetic components at each growth temperature, despite the differing temperature dependence of each process. As such, at higher temperatures photosynthetic nitrogen use efficiency increases more than A. Our results suggest C4 plants will show only modest changes in photosynthetic rates in response to changes in growth temperature, such as those expected within or between seasons, or the warming anticipated as a result of global climate change.

The effect of CO2 enrichment and irradiance on the growth, morphology and gas exchange of a C3 (Panicum laxum) and a C4 (Panicum antidotale) grass

Publisher: CSIRO Publishing

Date: 1997

DOI: 10.1071/PP96077

Abstract: The effect of CO2 enrichment and irradiance on the growth and gas exchange of two tropical grasses, Panicum laxum (C3) and Panicum antidotale (C4) were investigated. The two species were grown at either 350 (low) or 700 (high) µL L-1 CO2 concentration, under 40% (low) or 100% (high) of direct sunlight and supplied with le water and nutrition. Elevated CO2 enhanced plant dry weight at both irradiances in the C3 species (1.41-fold and 1.71-fold increase at low and high light, respectively) but only at high light in the C4 species (1.28 fold increase). CO2 enrichment had no effect on the dry weight of P. antidotale, when stem development was suppressed by growth under artificial lighting. When measured at the CO2 concentration at which they were grown, assimilation rates were similar in the low and high CO2 grown plants, for both species. However, when measurements made at low CO2 were compared, CO2 assimilation rates of the high light, high CO2 grown C3 and C4 species were lower than those of their low CO2 grown counterparts. High CO2 strongly reduced the stomatal conductance of both species, while it affected the Rubisco content (30% decrease) of the high light C3 species only. This work shows clearly that C4 species can respond to CO2 enrichment under favourable growth conditions, and that acclimation to elevated CO2 in pasture grasses does not necessarily involve accumulation of non-structural carbohydrates or reduction of total N or soluble proteins in source leaves.

Variations in nitrogen use efficiency reflect the biochemical subtype while variations in water use efficiency reflect the evolutionary lineage of C4 grasses at inter-glacial CO2

Publisher: Wiley

Date: 21-12-2016

DOI: 10.1111/PCE.12636

Abstract: C4 photosynthesis evolved multiple times in erse lineages. Most physiological studies comparing C4 plants were not conducted at the low atmospheric CO2 prevailing during their evolution. Here, 24 C4 grasses belonging to three biochemical subtypes [nicotinamide adenine dinucleotide malic enzyme (NAD-ME), phosphoenolpyruvate carboxykinase (PCK) and nicotinamide adenine dinucleotide phosphate malic enzyme (NADP-ME)] and six major evolutionary lineages were grown under ambient (400 μL L(-1) ) and inter-glacial (280 μL L(-1) ) CO2 . We hypothesized that nitrogen-related and water-related physiological traits are associated with subtypes and lineages, respectively. Photosynthetic rate and stomatal conductance were constrained by the shared lineage, while variation in leaf mass per area (LMA), leaf N per area, plant dry mass and plant water use efficiency were influenced by the subtype. Subtype and lineage were equally important for explaining variations in photosynthetic nitrogen use efficiency (PNUE) and photosynthetic water use efficiency (PWUE). CO2 treatment impacted most parameters. Overall, higher LMA and leaf N distinguished the Chloridoideae/NAD-ME group, while NADP-ME and PCK grasses were distinguished by higher PNUE regardless of lineage. Plants were characterized by high photosynthesis and PWUE when grown at ambient CO2 and by high conductance at inter-glacial CO2 . In conclusion, the evolutionary and biochemical ersity among C4 grasses was aligned with discernible leaf physiology, but it remains unknown whether these traits represent ecophysiological adaptation.

Leaf pigments and photosystems stoichiometry underpin photosynthetic efficiency of related C₃, C–C₄ and C₄ grasses under shade

Publisher: Wiley

Date: 11-2022

DOI: 10.1111/PPL.13819

Abstract: The quantum yield of photosynthesis ( QY , CO 2 fixed per light absorbed) depends on the efficiency of light absorption, the coupling between light absorption and electron transport, and the coupling between electron transport and carbon metabolism. QY is generally lower in C 3 relative to C 4 plants at warm temperatures and differs among the C 4 subtypes. We investigated the acclimation to shade of light absorption and electron transport in six representative grasses with C 3 , C 3 –C 4 and C 4 photosynthesis. Plants were grown under full (control) or 25% (shade) sunlight. We measured the in vivo activity and stoichiometry of PSI and PSII, leaf spectral properties and pigment contents, and photosynthetic enzyme activities. Under control growth‐light conditions, C 4 species had higher CO 2 assimilation rates, which declined to a greater extent relative to the C 3 species. Whole leaf PSII/PSI ratios were highest in the C 3 species, while QY and cyclic electron flow (CEF) were highest in the C 4 , NADP‐ME species. Shade significantly reduced leaf PSII/PSI, linear electron flow (LEF) and CEF of most species. Overall, shade reduced leaf absorptance, especially in the green region, as well as carotenoid and chlorophyll contents in C 4 more than non‐C 4 species. The NAD‐ME species underwent the greatest reduction in leaf absorptance and pigments under shade. In conclusion, shade compromised QY the least in the C 3 and the most in the C 4 ‐NAD‐ME species. Different sensitivity to shade was associated with the ability to maintain leaf absorptance and pigments. This is important for maximising light absorption and minimising photoprotection under low light.

Leaf age and eCO2 both influence photosynthesis by increasing light harvesting in mature Eucalyptus tereticornis at EucFACE

Publisher: Elsevier BV

Date: 11-2019

DOI: 10.1016/J.ENVEXPBOT.2019.103857

Lower photorespiration in elevated CO₂ reduces leaf N concentrations in mature Eucalyptus trees in the field

Publisher: Wiley

Date: 20-02-2019

DOI: 10.1111/GCB.14555

Abstract: Rising atmospheric CO

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

Publisher: Oxford University Press (OUP)

Date: 09-02-2011

DOI: 10.1093/JXB/ERR005

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

The sensitivity of photosynthesis to phosphorus deficiency differs between C3 and C4 tropical grasses

Publisher: CSIRO Publishing

Date: 2008

DOI: 10.1071/FP07256

Abstract: Phosphorus (P) is an important determinant of plant productivity, particularly in the tropical grasslands of Australia, which contain both C3 and C4 species. Few studies have compared the responses of such species to P deficiency. Previous work led us to hypothesise that C3 photosynthesis and the three subtypes of C4 photosynthesis have different sensitivities to P deficiency. To examine their dynamic response to P deficiency in more detail, four taxonomically related tropical grasses (Panicum laxum (C3) and Panicum coloratum, Cenchrus ciliaris and Panicum maximum belonging to the C4 subtypes NAD-ME, NADP-ME and PCK, respectively) were grown under contrasting P supplies, including P withdrawal from the growing medium. Changes in photosynthesis and growth were compared with leaf carbohydrate contents and metabolic fingerprints obtained using high-resolution proton nuclear magnetic resonance (1H-NMR). The response of CO2 assimilation rates to leaf contents of inorganic phosphate ([Pi]) was linear in the C3 grass, but asymptotic for the three C4 grasses. Relative growth rate was affected most by low P in the C3 species and was correlated with the leaf content of glucose 6-phosphate more than with carbohydrates. Principal component analysis of the 1H-NMR spectra revealed distinctive profiles of carbohydrates and amino acids for the four species. Overall, the data showed that photosynthesis of the three C4 subtypes behaved similarly. Compared with the C3 counterpart, photosynthesis of the three C4 grasses had a higher P use efficiency and lower Pi requirement, and responded to a narrower range of [Pi]. Although each of the four grass species showed distinctive 1H-NMR fingerprints, there were no differences in response that could be attributed to the C4 subtypes.

Smart glass impacts stomatal sensitivity of greenhouse Capsicum through altered light

Publisher: Oxford University Press (OUP)

Date: 23-01-2021

DOI: 10.1093/JXB/ERAB028

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

Midday water use efficiency in sorghum is linked to faster stomatal closure rate, lower stomatal aperture and higher stomatal density

Publisher: Wiley

Date: 22-06-2023

DOI: 10.1111/TPJ.16346

Abstract: Most studies assume midday gas exchange measurements capture the leaf's daytime performance. However, stomatal conductance ( g s ) and photosynthesis ( A n ) fluctuate diurnally due to endogenous and environmental rhythms, which can affect intrinsic water use efficiency ( iWUE ). Six Sorghum lines with contrasting stomatal anatomical traits were grown in environmentally controlled conditions, and leaf gas exchange was measured three times a day. Stomatal anatomy and kinetic responses to light transients were also measured. The highest A n and g s and the lowest iWUE were observed at midday for most lines. Diurnally averaged iWUE correlated positively with morning and midday iWUE and negatively with the time taken for stomata to close after transition to low light intensity ( k close ). There was significant variation among sorghum lines for k close , and smaller k close correlated with lower g s and higher stomatal density ( SD ) across the lines. In turn, g s was negatively correlated with SD and regulated by the operational stomatal aperture regardless of stomatal size. Altogether, our data suggest a common physiology to improve iWUE in sorghum related to the control of water loss without impacting photosynthesis relying on higher SD , lower stomatal aperture and faster stomatal closing in response to low light intensity.

Optimal stomatal behaviour around the world

Publisher: Springer Science and Business Media LLC

Date: 02-03-2015

DOI: 10.1038/NCLIMATE2550

Photosynthesis of C3, C3-C4, and C 4 grasses at glacial CO2

Publisher: Oxford University Press (OUP)

Date: 10-04-2014

DOI: 10.1093/JXB/ERU155

Transpiration influences cadmium uptake by baby leaf Spinach (Spinacia Oleracea L.)

Publisher: Science Publications

Date: 04-2014

DOI: 10.3844/AJABSSP.2014.523.533

Genotypic variation in transpiration efficiency due to differences in photosynthetic capacity among sugarcane-related clones

Publisher: Oxford University Press (OUP)

Date: 04-2017

DOI: 10.1093/JXB/ERX107

Cyclic electron flow and light partitioning between the two photosystems in leaves of plants with different functional types

Publisher: Springer Science and Business Media LLC

Date: 13-09-2019

DOI: 10.1007/S11120-019-00666-1

Abstract: Cyclic electron flow (CEF) around photosystem I (PSI) is essential for generating additional ATP and enhancing efficient photosynthesis. Accurate estimation of CEF requires knowledge of the fractions of absorbed light by PSI ( f I ) and PSII ( f II ), which are only known for a few model species such as spinach. No measures of f I are available for C 4 grasses under different irradiances. We developed a new method to estimate (1) f II in vivo by concurrently measuring linear electron flux through both photosystems $$\\left( {{\\text{LEF}}_{{{\\text{O}}_{ 2} }} } \\right)$$ LEF O 2 in leaf using membrane inlet mass spectrometry (MIMS) and total electron flux through PSII (ETR2) using chlorophyll fluorescence by a Dual-PAM at low light and (2) CEF as ETR1— $${\\text{LEF}}_{{{\\text{O}}_{ 2} }}$$ LEF O 2 . For a C 3 grass, f I was 0.5 and 0.4 under control (high light) and shade conditions, respectively. C 4 species belonging to NADP-ME and NAD-ME subtypes had f I of 0.6 and PCK subtype had 0.5 under control. All shade-grown C 4 species had f I of 0.6 except for NADP-ME grass which had 0.7. It was also observed that f I ranged between 0.3 and 0.5 for gymnosperm, liverwort and fern species. CEF increased with irradiance and was induced at lower irradiances in C 4 grasses and fern relative to other species. CEF was greater in shade-grown plants relative to control plants except for C 4 NADP-ME species. Our study reveals a range of CEF and f I values in different plant functional groups. This variation must be taken into account for improved photosynthetic calculations and modelling.

C4 photosynthesis and water stress

Publisher: Oxford University Press (OUP)

Date: 20-05-2009

DOI: 10.1093/AOB/MCN093

Prospects for improving CO2 fixation in C3-crops through understanding C4-Rubisco biogenesis and catalytic diversity

Publisher: Elsevier BV

Date: 06-2016

DOI: 10.1016/J.PBI.2016.04.002

Abstract: By operating a CO2 concentrating mechanism, C4-photosynthesis offers highly successful solutions to remedy the inefficiency of the CO2-fixing enzyme Rubisco. C4-plant Rubisco has characteristically evolved faster carboxylation rates with low CO2 affinity. Owing to high CO2 concentrations in bundle sheath chloroplasts, faster Rubisco enhances resource use efficiency in C4 plants by reducing the energy and carbon costs associated with photorespiration and lowering the nitrogen investment in Rubisco. Here, we show that C4-Rubisco from some NADP-ME species, such as maize, are also of potential benefit to C3-photosynthesis under current and future atmospheric CO2 pressures. Realizing this bioengineering endeavour necessitates improved understanding of the biogenesis requirements and catalytic variability of C4-Rubisco, as well as the development of transformation capabilities to engineer Rubisco in a wider variety of food and fibre crops.

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

Publisher: Wiley

Date: 08-02-2019

DOI: 10.1111/NPH.15668

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

Chapter 9 The Outlook for C4 Crops in Future Climate Scenarios

Publisher: Springer International Publishing

Date: 2021

DOI: 10.1007/978-3-030-64926-5_9

Mesophyll-specific overexpressing ofSvHXK6gene improves water use efficiency without yield loss in C4Setaria viridis

Publisher: Cold Spring Harbor Laboratory

Date: 11-07-2023

DOI: 10.1101/2023.07.10.548403

Abstract: Hexokinases (HXK) were the first sugar signalling proteins identified in plants and are well known for their feedback regulation of photosynthetic gene expression. In some C 3 plants, HXKs have been found to regulate stomatal function. However, the role of HXK in C 4 photosynthesis, which is inherently more water use efficient than C 3 metabolism, remains poorly understood. Here, we report on the first tissue-specific modification of HXK in a C 4 plant. SvHXK6 was expressed in the model C 4 grass Setaria viridis under the control of the ZmPEPC promoter ( ZmPEPC pro ), which directs expression in the leaf mesophyll tissue. Three S. viridis transgenic lines with increased abundance of SvHXK6 transcripts in the leaf tissue showed significant reduction in stomatal conductance with minimal effects on leaf CO 2 assimilation rate. Consequently, the transgenic lines had higher leaf-level water use efficiency relative to the control (wild-type and null) plants. Overexpression of SvHXK6 had no effect on shoot biomass or seed yield of the S. viridis plants. Our study shows conserved function of HXK in regulating stomatal conductance in a C 4 grass, demonstrating possible widespread utility in improving water use efficiency in C 4 as well as C 3 species.

Key physiological traits for drought tolerance identified through phenotyping a large set of slicing cucumber (Cucumis sativus L.) genotypes under field and water-stress conditions

Publisher: Springer Science and Business Media LLC

Date: 28-09-2023

DOI: 10.1007/S10722-023-01737-Y

C4 photosynthesis: 50 years of discovery and innovation

Publisher: Oxford University Press (OUP)

Date: 2017

DOI: 10.1093/JXB/ERW491

Comparative analysis of thylakoid protein complexes in the mesophyll and bundle sheath cells from C3 , C4 and C3 -C4 Paniceae grasses.

Publisher: Wiley

Date: 23-04-2019

DOI: 10.1111/PPL.12956

Abstract: To better understand the coordination between dark and light reactions during the transition from C

A common thermal niche among geographically diverse populations of the widely distributed tree species Eucalyptus tereticornis: No evidence for adaptation to climate-of-origin

Publisher: Wiley

Date: 08-07-2017

DOI: 10.1111/GCB.13771

Abstract: Impacts of climate warming depend on the degree to which plants are constrained by adaptation to their climate-of-origin or exhibit broad climatic suitability. We grew cool-origin, central and warm-origin provenances of Eucalyptus tereticornis in an array of common temperature environments from 18 to 35.5°C to determine if this widely distributed tree species consists of geographically contrasting provenances with differentiated and narrow thermal niches, or if provenances share a common thermal niche. The temperature responses of photosynthesis, respiration, and growth were equivalent across the three provenances, reflecting a common thermal niche despite a 2,200 km geographic distance and 13°C difference in mean annual temperature at seed origin. The temperature dependence of growth was primarily mediated by changes in leaf area per unit plant mass, photosynthesis, and whole-plant respiration. Thermal acclimation of leaf, stem, and root respiration moderated the increase in respiration with temperature, but acclimation was constrained at high temperatures. We conclude that this species consists of provenances that are not differentiated in their thermal responses, thus rejecting our hypothesis of adaptation to climate-of-origin and suggesting a shared thermal niche. In addition, growth declines with warming above the temperature optima were driven by reductions in whole-plant leaf area and increased respiratory carbon losses. The impacts of climate warming will nonetheless vary across the geographic range of this and other such species, depending primarily on each provenance's climate position on the temperature response curves for photosynthesis, respiration, and growth.

Investigating the NAD-ME biochemical pathway within C4 grasses using transcript and amino acid variation in C4 photosynthetic genes

Publisher: Springer Science and Business Media LLC

Date: 04-08-2018

DOI: 10.1007/S11120-018-0569-X

Abstract: Expanding knowledge of the C

Industrial-age changes in atmospheric [CO2] and temperature differentially alter responses of faster- and slower-growing Eucalyptus seedlings to short-term drought

Publisher: Oxford University Press (OUP)

Date: 05-2013

DOI: 10.1093/TREEPHYS/TPT032

Abstract: Climate change may alter forest composition by differentially affecting the responses of faster- and slower-growing tree species to drought. However, the combined effects of rising atmospheric CO2 concentration ([CO2]) and temperature on drought responses of trees are poorly understood. Here, we examined interactive effects of temperature (ambient, ambient + °C) and [CO2] (290, 400 and 650mu l l(-1)) on drought responses of Eucalyptus saligna Sm. (faster-growing) and E. sideroxylon A. Cunn. ex Woolls (slower-growing) seedlings. Drought was imposed via a controlled reduction in soil water over 1-2 weeks, re-watering seedlings when leaves visibly wilted. In ambient temperature, the effect of drought on the light-saturated net photosynthetic rate (Asat) in E. saligna decreased as [CO2] increased from pre-industrial to future concentrations, but rising [CO2] did not affect the response in Eucalyptus sideroxylon. In contrast, elevated temperature exacerbated the effect of drought in reducing Asat in both species. The drought response of Asat reflected changes in stomatal conductance (gs) associated with species and treatment differences in (i) utilization of soil moisture and (ii) leaf area ratio (leaf area per unit plant dry mass). Across [CO2] and temperature treatments, E. saligna wilted at higher soil water potentials compared with E. sideroxylon. Photosynthetic recovery from drought was 90% complete 2 days following re-watering across all species and treatments. Our results suggest that E. saligna (faster-growing) seedlings are more susceptible to drought than E. sideroxylon (slower-growing) seedlings. The greater susceptibility to drought of E. saligna reflected faster drawdown of soil moisture, associated with more leaf area and leaf area ratio, and the ability of E. sideroxylon to maintain higher gs at a given soil moisture. Inclusion of a pre-industrial [CO2] treatment allowed us to conclude that susceptibility of these species to short-term drought under past and future climates may be regulated by the same mechanisms. Further, the beneficial effects of rising [CO2] and deleterious effects of elevated temperature on seedling response to drought were generally offsetting, suggesting susceptibility of seedlings of these species to short-term drought in future climates that is similar to pre-industrial and current climate conditions.

Carbon isotope discrimination as a tool to explore C4 photosynthesis

Publisher: Oxford University Press (OUP)

Date: 06-04-2014

DOI: 10.1093/JXB/ERU127

Abstract: Photosynthetic carbon isotope discrimination is a non-destructive tool for investigating C4 metabolism. Tuneable diode laser absorption spectroscopy provides new opportunities for making rapid, concurrent measurements of carbon isotope discrimination and CO2 assimilation over a range of environmental conditions, and this has facilitated the use of carbon isotope discrimination as a probe of C4 metabolism. In spite of the significant progress made in recent years, understanding how photosynthetic carbon isotope discrimination measured concurrently with gas exchange relates to carbon isotope composition of leaf and plant dry matter remains a challenge that requires resolution if this technique is to be successfully applied as a screening tool in crop breeding and phylogenetic research. In this review, we update our understanding of the factors and assumptions that underlie variations in photosynthetic carbon isotope discrimination in C4 leaves. Closing the main gaps in our understanding of carbon isotope discrimination during C4 photosynthesis may help advance research aimed at developing higher productivity and efficiency in key C4 food, feed, and biofuel crops.

Water availability affects seasonal CO2-induced photosynthetic enhancement in herbaceous species in a periodically dry woodland

Publisher: Wiley

Date: 10-07-2017

DOI: 10.1111/GCB.13778

Abstract: Elevated atmospheric CO

Global change impacts on native pastures in south-east Queensland, Australia

Publisher: Elsevier BV

Date: 1999

DOI: 10.1016/S1364-8152(98)00082-6

Intrinsic water use efficiency depends on stomatal aperture rather than stomatal density in C₃ and C₄ grasses grown at glacial CO₂ and low light

Publisher: Cold Spring Harbor Laboratory

Date: 25-07-2021

DOI: 10.1101/2021.07.22.453465

Abstract: We investigated how stomatal morphology and physiology control intrinsic leaf water use efficiency ( iWUE ) in grasses. Two C 3 and six C 4 grasses were grown at ambient (400 µl L -1 ) or glacial CO 2 (180 µl L -1 ) and high (1000 µmol m -2 s -1 ) or low light intensity (200 µmol m -2 s -1 ). C 4 grasses tended to have higher iWUE and CO 2 assimilation rates, and lower stomatal conductance (g s ), operational stomatal aperture ( a op ) and guard cell K + influx rate relative to C 3 grasses, while stomatal size (SS) and stomatal density (SD) did not vary according to the photosynthetic type. Overall, iWUE and g s depended most on a op and density of open stomata. In turn, a op correlated with K + influx, stomatal opening speed on transition to high light and SS. Species with higher SD had smaller and faster-opening stomata. Although C 4 grasses operated with lower g s and a op at ambient CO 2 , they showed a greater potential to open stomata relative to maximal stomatal conductance (g max ), indicating heightened stomatal sensitivity and control. We uncover novel links between a op , g s , iWUE and K + influx amongst grasses and differential K + influx responses of C 4 guard cells to low light, revealing molecular targets for breeding crops with high iWUE . Across C 3 and six C 4 grasses, intrinsic water use efficiency was strongly associated with stomatal conductance, operational stomatal aperture, guard cell K + influx and stomatal opening speed on transition to high light.

Spatial expression patterns of genes encoding sugar sensors in leaves of C4 and C3 grasses

Publisher: Oxford University Press (OUP)

Date: 27-04-2023

DOI: 10.1093/AOB/MCAD057

Abstract: The mechanisms of sugar sensing in grasses remain elusive, especially those using C4 photosynthesis even though a large proportion of the world's agricultural crops utilize this pathway. We addressed this gap by comparing the expression of genes encoding components of sugar sensors in C3 and C4 grasses, with a focus on source tissues of C4 grasses. Given C4 plants evolved into a two-cell carbon fixation system, it was hypothesized this may have also changed how sugars were sensed. For six C3 and eight C4 grasses, putative sugar sensor genes were identified for target of rapamycin (TOR), SNF1-related kinase 1 (SnRK1), hexokinase (HXK) and those involved in the metabolism of the sugar sensing metabolite trehalose-6-phosphate (T6P) using publicly available RNA deep sequencing data. For several of these grasses, expression was compared in three ways: source (leaf) versus sink (seed), along the gradient of the leaf, and bundle sheath versus mesophyll cells. No positive selection of codons associated with the evolution of C4 photosynthesis was identified in sugar sensor proteins here. Expressions of genes encoding sugar sensors were relatively ubiquitous between source and sink tissues as well as along the leaf gradient of both C4 and C3 grasses. Across C4 grasses, SnRK1β1 and TPS1 were preferentially expressed in the mesophyll and bundle sheath cells, respectively. Species-specific differences of gene expression between the two cell types were also apparent. This comprehensive transcriptomic study provides an initial foundation for elucidating sugar-sensing genes within major C4 and C3 crops. This study provides some evidence that C4 and C3 grasses do not differ in how sugars are sensed. While sugar sensor gene expression has a degree of stability along the leaf, there are some contrasts between the mesophyll and bundle sheath cells.

Shade compromises the photosynthetic efficiency of NADP-ME less than that of PEP-CK and NAD-ME C4 grasses

Publisher: Oxford University Press (OUP)

Date: 05-04-2018

DOI: 10.1093/JXB/ERY129

Elevated CO2 increases the leaf temperature of two glasshouse-grown C4 grasses

Publisher: CSIRO Publishing

Date: 2002

DOI: 10.1071/FP02075

Abstract: This study investigates the effect of elevated CO2 partial pressure (pCO2)-induced stomatal closure on leaf temperature and gas exchange of C4 grasses. Two native Australian C4 grasses, Astrebla lappacea (Lindl.) Domin and Bothriochloa bladhii Kuntze, were grown at three different pCO2 (35, 70 and 120 Pa) in three matched, temperature-controlled glasshouse compartments. The difference between leaf and air temperature (ΔT) was monitored diurnally with thermocouples. ΔT increased with both step-increases of ambient pCO2. Average noon leaf temperature increased by 0.4 and 0.3°C for A. lappacea with the 35–70 and 70–120 Pa steps of pCO2 elevation, respectively. For B. bladhii, the increases were 0.5°C for both pCO2 steps. ΔT was strongly dependent on irradiance, pCO2 and air humidity. Leaf gas exchange was measured at constant temperature and high irradiance at the three growth pCO2. Under these conditions, CO2 assimilation saturated at 70 Pa, while stomatal conductance decreased by the same extent (0.58-fold) with both step-increases in pCO2, suggesting that whole-plant water use efficiency of C4 grasses would increase beyond a doubling of ambient pCO2. The ratio of intercellular to ambient pCO2 was not affected by short- or long-term doubling or near-tripling of pCO2, in either C4 species when measured under standard conditions.

A global perspective of ground level, 'ambient' carbon dioxide for assessing the response of plants to atmospheric CO2

Publisher: Wiley

Date: 10-2001

DOI: 10.1046/J.1365-2486.2001.00436.X

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

Publisher: Wiley

Date: 06-11-2014

DOI: 10.1111/GCB.12729

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

Light-altering cover materials and sustainable greenhouse production of vegetables: a review

Publisher: Springer Science and Business Media LLC

Date: 11-06-2021

DOI: 10.1007/S10725-021-00723-7

Adaptation of plants to a high CO2 and high-temperature world

Publisher: Springer Science and Business Media LLC

Date: 11-2022

DOI: 10.1007/S11103-022-01310-8

Sugar sensing responses to low and high light in leaves of the C4 model grass Setaria viridis

Publisher: Oxford University Press (OUP)

Date: 02-11-2019

DOI: 10.1093/JXB/ERZ495

Abstract: ABSTRACT :Although sugar regulate photosynthesis, the signalling pathways underlying this process remain elusive, especially for C4 crops. To address this knowledge gap and identify potential candidate genes, we treated Setaria viridis (C4 model) plants acclimated to medium light intensity (ML, 500 µmol m-2 s-1) with low (LL, 50 µmol m-2 s-1) or high (HL, 1000 µmol m-2 s-1) light for 4 days and observed the consequences on carbon metabolism and the transcriptome of source leaves. LL impaired photosynthesis and reduced leaf content of signalling sugars (glucose, sucrose and trehalose-6-phosphate). Contrastingly, HL strongly induced sugar accumulation without repressing photosynthesis. LL more profoundly impacted leaf transcriptome, including photosynthetic genes. LL and HL contrastingly altered the expression of HXK and SnRK1 sugar sensors and trehalose pathway genes. The expression of key target genes of HXK and SnRK1 were affected by LL and sugar depletion, while surprisingly HL and strong sugar accumulation only slightly repressed the SnRK1 signalling pathway. In conclusion, we demonstrate that LL profoundly impacted photosynthesis and the transcriptome of S. viridis source leaves, while HL altered sugar levels more than LL. We also present the first evidence that sugar signalling pathways in C4 source leaves may respond to light intensity and sugar accumulation differently to C3 source leaves.

Short-term thermal photosynthetic responses of C4 grasses are independent of the biochemical subtype

Publisher: Oxford University Press (OUP)

Date: 09-2017

DOI: 10.1093/JXB/ERX350

Chapter 8 Nitrogen and Water Use Efficiency of C4 Plants

Publisher: Springer Netherlands

Date: 2010

DOI: 10.1007/978-90-481-9407-0_8

The growth response of C4 plants to rising atmospheric CO2 partial pressure: A reassessment

Publisher: Wiley

Date: 09-2000

DOI: 10.1046/J.1365-3040.2000.00609.X

Simultaneous determination of Rubisco carboxylase and oxygenase kinetic parameters in Triticum aestivum and Zea mays using membrane inlet mass spectrometry

Publisher: Wiley

Date: 03-2010

DOI: 10.1111/J.1365-3040.2009.02095.X

Abstract: The lack of complete Rubisco kinetic data for numerous species is partly because of the time consuming nature of the multiple methods needed to assay all of the Rubisco parameters. We have developed a membrane inlet mass spectrometer method that simultaneously determines the rate of Rubisco carboxylation (v(c)) and oxygenation (v(o)), and the CO(2) and O(2) concentrations. Using the collected data, the Michaels-Menten equations for v(c) and v(o) in response to changing CO(2) and O(2) concentrations were simultaneously solved for the CO(2) (K(c)) and O(2) (K(o)) constants, the maximum turnover rates of the enzyme for CO(2) (kcat(CO2)) and O(2) (kcat(O2)) and the specificity for CO(2) relative to O(2) (S(c/o)). In the C(4) species Zea mays K(c) was higher but K(o) was lower compared with the C(3) species Triticum aestivum. The kcat(CO2) was higher and the kcat(O2) lower in Z. mays compared with T. aestivum and S(c/o) was similar in the two species. The V(omax)/V(cmax) was lower in Z. mays and thus did not correlate with changes in S(c/o). In conclusion, this mass spectrometer system provides a means of simultaneously determining the important Rubisco kinetic parameters, K(c), K(o), kcat(CO2,)kcat(O2) and S(c/o) from the same set of assays.

Smart Film Impacts Stomatal Sensitivity of Greenhouse Capsicum Through Altered Light

Publisher: Cold Spring Harbor Laboratory

Date: 24-09-2020

DOI: 10.1101/2020.09.22.309427

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

Photosynthetic capacity and leaf nitrogen decline along a controlled climate gradient in provenances of two widely distributed Eucalyptus species

Publisher: Wiley

Date: 19-06-2018

DOI: 10.1111/GCB.14330

Abstract: Climate is an important factor limiting tree distributions and adaptation to different thermal environments may influence how tree populations respond to climate warming. Given the current rate of warming, it has been hypothesized that tree populations in warmer, more thermally stable climates may have limited capacity to respond physiologically to warming compared to populations from cooler, more seasonal climates. We determined in a controlled environment how several provenances of widely distributed Eucalyptus tereticornis and E. grandis adjusted their photosynthetic capacity to +3.5°C warming along their native distribution range (~16-38°S) and whether climate of seed origin of the provenances influenced their response to different growth temperatures. We also tested how temperature optima (T

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.

Photosynthetic oxygen exchange in C4 grasses: The role of oxygen as electron acceptor

Publisher: Wiley

Date: 20-10-2003

DOI: 10.1046/J.1365-3040.2003.01112.X

Convergent acclimation of leaf photosynthesis and respiration to prevailing ambient temperatures under current and warmer climates in Eucalyptus tereticornis

Publisher: Wiley

Date: 10-06-2016

DOI: 10.1111/NPH.14035

Abstract: Understanding physiological acclimation of photosynthesis and respiration is important in elucidating the metabolic performance of trees in a changing climate. Does physiological acclimation to climate warming mirror acclimation to seasonal temperature changes? We grew Eucalyptus tereticornis trees in the field for 14 months inside 9‐m tall whole‐tree chambers tracking ambient air temperature ( T air ) or ambient T air + 3°C (i.e. ‘warmed’). We measured light‐ and CO 2 ‐saturated net photosynthesis ( A max ) and night‐time dark respiration ( R ) each month at 25°C to quantify acclimation. Tree growth was measured, and leaf nitrogen (N) and total nonstructural carbohydrate (TNC) concentrations were determined to investigate mechanisms of acclimation. Warming reduced A max and R measured at 25°C compared to ambient‐grown trees. Both traits also declined as mean daily T air increased, and did so in a similar way across temperature treatments. A max and R (at 25°C) both increased as TNC concentrations increased seasonally these relationships appeared to arise from source–sink imbalances, suggesting potential substrate regulation of thermal acclimation. We found that photosynthesis and respiration each acclimated equivalently to experimental warming and seasonal temperature change of a similar magnitude, reflecting a common, nearly homeostatic constraint on leaf carbon exchange that will be important in governing tree responses to climate warming.

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

Publisher: Oxford University Press (OUP)

Date: 27-06-2011

DOI: 10.1093/TREEPHYS/TPR049

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

Anatomical drivers of stomatal conductance in sorghum lines with different leaf widths grown under different temperatures

Publisher: Wiley

Date: 17-04-2023

DOI: 10.1111/PCE.14592

Abstract: Sustaining crop productivity and resilience in water‐limited environments and under rising temperatures are matters of concern worldwide. We investigated the leaf anatomical traits that underpin our recently identified link between leaf width (LW) and intrinsic water use efficiency (iWUE), as traits of interest in plant breeding. Ten sorghum lines with varying LW were grown under three temperatures to expand the range of variation of both LW and gas exchange rates. Leaf gas exchange, surface morphology and cross‐sectional anatomy were measured and analysed using structural equations modelling. Narrower leaves had lower stomatal conductance ( g s ) and higher iWUE across growth temperatures. They also had smaller intercellular airspaces, stomatal size, percentage of open stomatal aperture relative to maximum, hydraulic pathway, mesophyll thickness, and leaf mass per area. Structural modelling revealed a developmental association among leaf anatomical traits that underpinned g s variation in sorghum. Growing temperature and LW both impacted leaf gas exchange rates, but only LW directly impacted leaf anatomy. Wider leaves may be more productive under well‐watered conditions, but consume more water for growth and development, which is detrimental under water stress.

Photosynthetic flexibility in maize exposed to salinity and shade

Publisher: Oxford University Press (OUP)

Date: 04-2014

DOI: 10.1093/JXB/ERU130

Improved analysis of C₄and C₃photosynthesis via refinedin vitroassays of their carbon fixation biochemistry

Publisher: Oxford University Press (OUP)

Date: 27-04-2016

DOI: 10.1093/JXB/ERW154

The transcriptomic responses of C₄ grasses to subambient CO₂ and low light are largely species specific and only refined by photosynthetic subtype

Publisher: Wiley

Date: 03-12-2020

DOI: 10.1111/TPJ.14583

Abstract: Three subtypes of C

Smart Glass Film Reduced Ascorbic Acid in Red and Orange Capsicum Fruit Cultivars without Impacting Shelf Life

Publisher: MDPI AG

Date: 04-04-2022

DOI: 10.3390/PLANTS11070985

Abstract: Smart Glass Film (SGF) is a glasshouse covering material designed to permit 80% transmission of photosynthetically active light and block heat-generating solar energy. SGF can reduce crop water and nutrient consumption and improve glasshouse energy use efficiency yet can reduce crop yield. The effect of SGF on the postharvest shelf life of fruits remains unknown. Two capsicum varieties, Red (Gina) and Orange (O06614), were cultivated within a glasshouse covered in SGF to assess fruit quality and shelf life during the winter season. SGF reduced cuticle thickness in the Red cultivar (5%) and decreased ascorbic acid in both cultivars (9–14%) without altering the overall morphology of the mature fruits. The ratio of total soluble solids (TSSs) to titratable acidity (TA) was significantly higher in Red (29%) and Orange (89%) cultivars grown under SGF. The Red fruits had a thicker cuticle that reduced water loss and extended shelf life when compared to the Orange fruits, yet neither water loss nor firmness were impacted by SGF. Reducing the storage temperature to 2 °C and increasing relative humidity to 90% extended the shelf life in both cultivars without evidence of chilling injury. In summary, SGF had minimal impact on fruit development and postharvest traits and did not compromise the shelf life of mature fruits. SGF provides a promising technology to block heat-generating solar radiation energy without affecting fruit ripening and marketable quality of capsicum fruits grown during the winter season.

Mehler reaction plays a role in C3 and C4 photosynthesis under shade and low CO2

Publisher: Springer Science and Business Media LLC

Date: 03-02-2021

DOI: 10.1007/S11120-021-00819-1

Leaf structural characteristics are less important than leaf chemical properties in determining the response of leaf mass per area and photosynthesis of Eucalyptus saligna to industrial-age changes in

Publisher: Oxford University Press (OUP)

Date: 21-08-2012

DOI: 10.1093/JXB/ERS231

Abstract: The rise in atmospheric [CO(2)] is associated with increasing air temperature. However, studies on plant responses to interactive effects of [CO(2)] and temperature are limited, particularly for leaf structural attributes. In this study, Eucalyptus saligna plants were grown in sun-lit glasshouses differing in [CO(2)] (290, 400, and 650 µmol mol(-1)) and temperature (26 °C and 30 °C). Leaf anatomy and chloroplast parameters were assessed with three-dimensional confocal microscopy, and the interactive effects of [CO(2)] and temperature were quantified. The relative influence of leaf structural attributes and chemical properties on the variation of leaf mass per area (LMA) and photosynthesis within these climate regimes was also determined. Leaf thickness and mesophyll size increased in higher [CO(2)] but decreased at the warmer temperature no treatment interaction was observed. In pre-industrial [CO(2)], warming reduced chloroplast diameter without altering chloroplast number per cell, but the opposite pattern (reduced chloroplast number per cell and unchanged chloroplast diameter) was observed in both current and projected [CO(2)]. The variation of LMA was primarily explained by total non-structural carbohydrate (TNC) concentration rather than leaf thickness. Leaf photosynthetic capacity (light- and [CO(2)]-saturated rate at 28 °C) and light-saturated photosynthesis (under growth [CO(2)] and temperature) were primarily determined by leaf nitrogen contents, while secondarily affected by chloroplast gas exchange surface area and chloroplast number per cell, respectively. In conclusion, leaf structural attributes are less important than TNC and nitrogen in affecting LMA and photosynthesis responses to the studied climate regimes, indicating that leaf structural attributes have limited capacity to adjust these functional traits in a changing climate.

A novel cover material improves cooling energy and fertigation efficiency for glasshouse eggplant production

Publisher: Elsevier BV

Date: 07-2022

DOI: 10.1016/J.ENERGY.2022.123871

Examination of pre-industrial and future [CO2] reveals the temperature-dependent CO2 sensitivity of light energy partitioning at PSII in eucalypts

Publisher: CSIRO Publishing

Date: 2010

DOI: 10.1071/FP10113

Abstract: We grew faster-growing Eucalyptus saligna Sm. and slower-growing Eucalyptus sideroxylon A. Cunn ex Woolls tree seedlings in sunlit glasshouses at all combinations of 290 µL L–1 (pre-industrial), 400 µL L–1 (modern) or 650 µL L–1 (future) global atmospheric CO2 ([CO2]), and ambient or ambient + 4°C temperature. To assess photosynthetic performance, we simultaneously measured light-saturated CO2 assimilation (Asat) and chlorophyll fluorescence emission along with the capacity for photosynthetic O2 evolution and leaf pigment composition. Photosynthetic response to [CO2] was similar between species. Increasing [CO2] but not temperature increased Asat. The response of photosynthetic electron transport to [CO2] was temperature-dependent and manifested through adjustments in energy partitioning at PSII. Increasing [CO2] resulted in greater PSII operating efficiencies at the elevated temperature. We observed no associated acclimatory adjustments in the capacity for photosynthetic O2 evolution or changes in leaf chlorophyll content. Photoprotective energy dissipation responded to increasing [CO2] and temperature. Across species and treatments, increased energy partitioning to electron transport was always associated with decreased partitioning to energy dissipation. Our results suggest that in response to increasing [CO2] and temperature, E. saligna and E. sideroxylon meet increased demands for the products of electron transport via adjustments in energy partitioning, not through acclimation of the capacity for photosynthetic electron transport or light absorption.

Nonstomatal limitations are responsible for drought‐induced photosynthetic inhibition in four C₄ grasses

Publisher: Wiley

Date: 24-07-2003

DOI: 10.1046/J.1469-8137.2003.00835.X

Heat stress prevented the biomass and yield stimulation caused by elevated CO₂ in two well-watered wheat cultivars

Publisher: Cold Spring Harbor Laboratory

Date: 22-11-2021

DOI: 10.1101/2021.11.21.469459

Abstract: To investigate the interactive effects of elevated CO 2 and heat stress (HS), we grew two contrasting wheat cultivars, early-maturing Scout and high-tillering Yitpi, under non-limiting water and nutrients at ambient (aCO 2 , 450 ppm) or elevated (eCO 2 , 650 ppm) CO 2 and 22°C in the glasshouse. Plants were exposed to two 3-day HS cycles at the vegetative (38.1°C) and/or flowering (33.5°C) stage. At aCO 2 , both wheat cultivars showed similar responses of photosynthesis and mesophyll conductance to temperature and produced similar grain yield. Relative to aCO 2 , eCO 2 enhanced photosynthesis rate and reduced stomatal conductance and maximal carboxylation rate ( V cmax ). During HS, high temperature stimulated photosynthesis at eCO 2 in both cultivars, while eCO 2 stimulated photosynthesis in Scout. Electron transport rate ( J max ) was unaffected by any treatment. eCO 2 equally enhanced biomass and grain yield of both cultivars in control, but not HS, plants. HS reduced biomass and yield of Scout at eCO 2 . Yitpi, the cultivar with higher grain nitrogen, underwent a trade-off between grain yield and nitrogen. In conclusion, eCO 2 improved photosynthesis of control and HS wheat, and improved biomass and grain yield of control plants only. Under well-watered conditions, HS was not detrimental to photosynthesis or growth but precluded a yield response to eCO 2 . High temperatures increased photosynthetic rates only at eCO 2 and photosynthesis was upregulated after recovery from heat stress at eCO 2 in Scout suggesting that eCO 2 increased optimum temperature of photosynthesis.

Elevated CO2 alleviates the negative impact of heat stress on wheat physiology but not on grain yield

Publisher: Oxford University Press (OUP)

Date: 24-08-2019

DOI: 10.1093/JXB/ERZ386

Abstract: Elevated CO2 protects wheat photosynthesis from heat stress damage via increased electron transport and facilitates recovery of photosynthesis and biomass but not the yield due to heat-induced grain abortion.

The role of leaf width and conductances to CO

Publisher: Wiley

Date: 06-07-2019

DOI: 10.1111/NPH.15920

Abstract: C

CO2 availability influences hydraulic function of C3 and C4 grass leaves

Publisher: Oxford University Press (OUP)

Date: 10-03-2018

DOI: 10.1093/JXB/ERY095

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

Publisher: Wiley

Date: 30-11-2018

DOI: 10.1111/NPH.15566

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

Light-limited photosynthesis under energy-saving film decreases eggplant yield

Publisher: Wiley

Date: 29-08-2020

DOI: 10.1002/FES3.245

Leaf pigments and photosystems stoichiometry underpin photosynthetic efficiency of related C₃, C₃-C₄ and C₄ grasses under shade

Publisher: Cold Spring Harbor Laboratory

Date: 09-10-2020

DOI: 10.1101/2020.10.08.330837

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

Publisher: CSIRO Publishing

Date: 2013

DOI: 10.1071/FP12130

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

Nitrogen deficiency precludes a growth response to CO2 enrichment in C3 and C4 Panicum grasses

Publisher: CSIRO Publishing

Date: 1998

DOI: 10.1071/PP98026

Abstract: We investigated the interaction of nitrogen (N) supply and CO2 enrichment on the growth and photosynthesis of Panicum laxum (C3), P. coloratum (C4) and P. antidotale (C4). Plants were grown at ambient CO2 partial pressures (pa) of either 36 (low) or 71 (high) Pa, in potted soil supplied with 0 (low) or 60 (high) mg N kg-1 soil week-1. Elevated CO2 enhanced total plant dry mass of all three species by approximately 28% under high N supply, but had no effect on biomass accumulation under N deficiency. CO2 enrichment resulted in reductions of CO2 assimilation rates (A measured at comparable pa) of P. laxum, indicating acclimation of photosynthesis. This acclimation, which was more pronounced under N stress, was unrelated to changes in leaf N or non-structural carbohydrate concentrations, because neither were affected by CO2 enrichment. In the C4 grasses grown at low N, A were fully saturated at the current ambient pa, whereas at high N, A increased slightly when CO2 was raised to 71 Pa. N deficiency reduced the initial slope of the CO2 response curve of A in P. antidotale, and this effect was more pronounced at high CO2. In conclusion, the preclusion of a growth response to CO2 enrichment by N deficiency was correlated with a strong inhibition of A in the C3 species, and the saturation of A at below current atmospheric pa in C4 species.

Moderate heat stress prevented the observed biomass and yield stimulation caused by elevated CO₂ in two well-watered wheat cultivars

Publisher: Springer Science and Business Media LLC

Date: 06-2022

DOI: 10.1007/S11103-022-01276-7

Abstract: Heat stress (HS) under well-watered conditions was not detrimental to leaf photosynthesis or yield but modified the elevated CO 2 response of photosynthesis and yield in two contrasting wheat cultivars. Climate change is increasing the frequency of extreme events such as heat waves, adversely affecting crop productivity. While positive impacts of elevated carbon dioxide (eCO 2 ) on crop productivity are evident, the interactive effects of eCO 2 and environmental stresses are still unclear. To investigate the interactive effects of elevated CO 2 and heat stress (HS), we grew two contrasting wheat cultivars, early-maturing Scout and high-tillering Yitpi, under non-limiting water and nutrients at ambient (aCO 2 , 450 ppm) or elevated (eCO 2 , 650 ppm) CO 2 and 22 °C in the glasshouse. Plants were exposed to two 3-day HS cycles at the vegetative (38.1 °C) and/or flowering (33.5 °C) stage. At aCO 2 , both wheat cultivars showed similar responses of photosynthesis and mesophyll conductance to temperature and produced similar grain yield. Relative to aCO 2 , eCO 2 enhanced photosynthesis rate and reduced stomatal conductance and maximal carboxylation rate ( V cmax ). During HS, high temperature stimulated photosynthesis at eCO 2 in both cultivars, while eCO 2 stimulated photosynthesis in Scout. Electron transport rate ( J max ) was unaffected by any treatment. eCO 2 equally enhanced biomass and grain yield of both cultivars in control, but not HS, plants. HS reduced biomass and yield of Scout at eCO 2 . Yitpi, the cultivar with higher grain nitrogen, underwent a trade-off between grain yield and nitrogen. In conclusion, eCO 2 improved photosynthesis of control and HS wheat, and improved biomass and grain yield of control plants only. Under well-watered conditions, HS was not detrimental to photosynthesis or growth but precluded a yield response to eCO 2 .

High vapour pressure deficit and low soil water availability enhance shoot growth responses of a C4 grass (Panicum coloratum cv. Bambatsi) to CO2 enrichment

Publisher: CSIRO Publishing

Date: 1998

DOI: 10.1071/PP97054

Abstract: The hypothesis that shoot growth responses of C4 grasses to elevated CO2 are dependent on shoot water relations was tested using a C4 grass, Panicum coloratum (NAD-ME subtype). Plants were grown for 35 days at CO2 concentrations of 350 or 1000 µL CO2 L-1. Shoot water relations were altered by growing plants in soil which was brought daily to 65, 80 or 100% field capacity (FC) and by maintaining the vapour pressure deficit (VPD) at 0.9 or 2.1 kPa. At 350 µL CO2 L-1, high VPD and lower soil water content depressed shoot dry mass, which declined in parallel at each VPD with decreasing soil water content. The growth depression at high VPD was associated with increased shoot transpiration, whereas at low soil water, leaf water potential was reduced. Elevated CO2 ameliorated the impact of both stresses by decreasing transpiration rates and raising leaf water potential. Consequently, high CO2 approximately doubled shoot mass and leaf length at a VPD of 2.1 kPa and soil water contents of 65 and 80% FC but had no effect on unstressed plants. Water use efficiency was enhanced by elevated CO2 under conditions of stress but this was primarily due to increases in shoot mass. High CO2 had a greater effect on leaf growth parameters than on stem mass. Elevated CO2 increased specific leaf area and leaf area ratio, the latter at high VPD only. We conclude that high CO2 increases shoot growth of C4 grasses by ameliorating the effects of stress induced by either high VPD or low soil moisture. Since these factors limit growth of field-grown C4 grasses, it is likely that their biomass will be enhanced by rising atmospheric CO2 concentrations.

The photosynthesis of young Panicum C4 leaves is not C3-like

Publisher: Wiley

Date: 11-1998

DOI: 10.1046/J.1365-3040.1998.00348.X

Anatomical drivers of stomatal conductance in sorghum lines with different leaf widths grown under different temperatures

Publisher: Cold Spring Harbor Laboratory

Date: 20-10-2022

DOI: 10.1101/2022.10.16.512409

Abstract: Improvements in leaf water use efficiency ( iWUE ) can maintain crop productivity in water limited environments under rising temperatures. We investigated the leaf anatomical traits which underpin our recently identified link between leaf width ( LW ) and iWUE . Ten sorghum lines with varying LW were grown under three temperatures to expand the range of variation of both LW and gas exchange rates. Leaf gas exchange, surface morphology and cross-sectional anatomy were measured and analysed using structural equations modelling. Narrower leaves had lower stomatal conductance ( g s ) and higher iWUE across growth temperatures. They also had smaller intercellular airspaces, stomatal size, percentage of open stomatal aperture relative to maximum, hydraulic pathway, mesophyll thickness, and leaf mass per area. Structural modelling revealed a developmental association among leaf anatomical traits that underpinned g s variation in sorghum. Growing temperature and LW both impacted leaf gas exchange rates, but only LW directly impacted leaf anatomy. Wider leaves may be more productive under well-watered conditions, but consume more water for growth and development, which is detrimental under water stress. Coordination between leaf width and leaf anatomy underpins stomatal conductance variation in sorghum grown under different temperatures.

Exposure to preindustrial, current and future atmospheric CO2 and temperature differentially affects growth and photosynthesis in Eucalyptus

Publisher: Wiley

Date: 02-12-2010

DOI: 10.1111/J.1365-2486.2009.02003.X

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

Publisher: Oxford University Press (OUP)

Date: 03-10-2013

DOI: 10.1111/1574-6941.12001

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

Guidelines for the use and interpretation of assays for monitoring autophagy

Publisher: Informa UK Limited

Date: 04-2012

DOI: 10.4161/AUTO.19496

How can we breed for more water use-efficient sugarcane?

Publisher: Oxford University Press (OUP)

Date: 02-2016

DOI: 10.1093/JXB/ERW009

Coordination of stomata and vein patterns with leaf width underpins water-use efficiency in a C

Publisher: Wiley

Date: 28-11-2022

DOI: 10.1111/PCE.14225

Abstract: Despite its importance for crop water use and productivity, especially in drought-affected environments, the underlying mechanisms of variation in intrinsic water-use efficiency (iWUE = net photosynthesis/stomatal conductance for water vapour, g

Soil moisture sensing with mmWave radar

Publisher: ACM

Date: 17-10-2022

DOI: 10.1145/3555077.3556472

An energy-saving glasshouse film reduces seasonal, and cultivar dependent Capsicum yield due to light limited photosynthesis

Publisher: Cold Spring Harbor Laboratory

Date: 31-10-2022

DOI: 10.1101/2022.10.29.513818

Abstract: Glasshouse films can be used to reduce energy costs by limiting non-productive heat-generating radiation, but the impact on yield of greenhouse horticultural crops remains unknown. The effects of energy-saving film ULR-80 (referred to as Smart Glass SG) designed to block long wavelength light that generates heat also reduced photosynthetically active radiation (PAR) consequently affecting crop morphology, photosynthesis, leaf pigments, and yield of two hydroponically grown capsicum ( Capsicum annuum L.) cultivars (Red and Orange). The crops were grown in four high-tech glasshouse bays over two seasons of similar daily light integrals (DLI) during ascending (Autumn) and descending (Summer) photoperiods. The Red cultivar exhibited higher photosynthetic rates (light saturated - A sat and maximal - A max ) and yield than the Orange cultivar in control but displayed stronger reductions in modelled photosynthetic rates at growth light and yield in SG without changes in photosynthetic capacity. Foliar pigment ratios of chlorophyll a/b and carotenoid: chlorophyll remained unaffected by the SG during both seasons indicating that chloroplast homeostasis was similar between SG and control. The seasonal differences in photosynthetic pigments and xanthophyll de-epoxidation state (DPS) revealed that cultivars were able to sense the SG-altered light environment during the ascending, but not descending photoperiod. The descending photoperiod correlated with a lower daily light level and a substantial yield reduction of 29 % and 13 % in Red and Orange cultivars, respectively. Thus, SG-induced higher reductions in yield during the descending photoperiod indicate that SG may be more beneficial for capsicum crops planted during Autumn with an ascending photoperiod. A potential energy saving SG film limited net photosynthesis of capsicum The SG film reduced yield of two capsicum cultivars that can be mitigated by planting during the low light growth season with a shorter photoperiod SG reduced genotype-dependent capsicum yield was associated with alterations in the level of foliar pigments required for photoprotection under adverse light conditions

Soil phosphorous and endogenous rhythms exert a larger impact than CO 2 or temperature on nocturnal stomatal conductance in Eucalyptus tereticornis

Publisher: Oxford University Press (OUP)

Date: 11-2013

DOI: 10.1093/TREEPHYS/TPT091

Abstract: High nocturnal transpiration rates (5-15% of total water loss in terrestrial plants) may be adaptive under limited fertility, by increasing nutrient uptake or transport via transpiration-induced mass flow, but the response of stomata in the dark to environmental variables is poorly understood. Here we tested the impact of soil phosphorous (P) concentration, atmospheric CO2 concentration and air temperature on stomatal conductance (gs) during early and late periods in the night, as well as at midday in naturally, sun-lit glasshouse-grown Eucalyptus tereticornis Sm. seedlings. Soil P was the main driver of nocturnal gs, which was consistently higher in low soil P (37.3-79.9 mmol m(-2) s(-1)) than in high soil P (17.7-49.3 mmol m(-2)(-1)). Elevated temperature had only a marginal (P = 0.07) effect on gs early in the night (gs decreased from 34.7 to 25.8 mmol m(-2) s(-1) with an increase in temperature of 4 °C). The effect of CO2 depended on its interaction with temperature. Stomatal conductance responses to soil P were apparently driven by indirect effects of soil P on plant anatomy, since gs was significantly and negatively correlated with wood density. However, the relationship of gs with environmental factors became weaker late in the night, relative to early in the night, likely due to apparent endogenous processes gs late in the night was two times larger than gs observed early in the night. Time-dependent controls over nocturnal gs suggest that daytime stomatal models may not apply during the night, and that different types of regulation may occur even within a single night. We conclude that the enhancement of nocturnal gs under low soil P availability is unlikely to be adaptive in our species because of the relatively small amount of transpiration-induced mass flow that can be achieved through rates of nocturnal water loss (3-6% of daytime mass flow).

High intrinsic water use efficiency is underpinned by high stomatal aperture and guard cell potassium flux in C3 and C4 grasses grown at glacial CO2 and low light

Publisher: Oxford University Press (OUP)

Date: 28-10-2021

DOI: 10.1093/JXB/ERAB477

Abstract: We compared how stomatal morphology and physiology control intrinsic leaf water use efficiency (iWUE) in two C3 and six C4 grasses grown at ambient (400 µmol mol–1) or glacial CO2 (180 µmol mol–1) and high (1000 µmol m–2 s–1) or low light intensity (200 µmol m–2 s–1). C4 grasses tended to have higher iWUE and CO2 assimilation rates, and lower stomatal conductance (gs), operational stomatal aperture (aop), and guard cell K+ influx rate relative to C3 grasses, while stomatal size (SS) and stomatal density (SD) did not vary according to the photosynthetic type. Overall, iWUE and gs depended most on aop and density of open stomata. In turn, aop correlated with K+ influx, stomatal opening speed on transition to high light, and SS. Species with higher SD had smaller and faster-opening stomata. Although C4 grasses operated with lower gs and aop at ambient CO2, they showed a greater potential to open stomata relative to maximal stomatal conductance (gmax), indicating heightened stomatal sensitivity and control. We uncovered promising links between aop, gs, iWUE, and K+ influx among C4 grasses, and differential K+ influx responses of C4 guard cells to low light, revealing molecular targets for improving iWUE in C4 crops.

The role of chloroplast movement in C4 photosynthesis: a theoretical analysis using a three-dimensional reaction–diffusion model for maize

Publisher: Oxford University Press (OUP)

Date: 21-04-2023

DOI: 10.1093/JXB/ERAD138

Abstract: Chloroplasts movement within mesophyll cells in C4 plants is hypothesized to enhance the CO2 concentrating mechanism, but this is difficult to verify experimentally. A three-dimensional (3D) leaf model can help analyse how chloroplast movement influences the operation of the CO2 concentrating mechanism. The first volumetric reaction–diffusion model of C4 photosynthesis that incorporates detailed 3D leaf anatomy, light propagation, ATP and NADPH production, and CO2, O2 and bicarbonate concentration driven by diffusional and assimilation/emission processes was developed. It was implemented for maize leaves to simulate various chloroplast movement scenarios within mesophyll cells: the movement of all mesophyll chloroplasts towards bundle sheath cells (aggregative movement) and movement of only those of interveinal mesophyll cells towards bundle sheath cells (avoidance movement). Light absorbed by bundle sheath chloroplasts relative to mesophyll chloroplasts increased in both cases. Avoidance movement decreased light absorption by mesophyll chloroplasts considerably. Consequently, total ATP and NADPH production and net photosynthetic rate increased for aggregative movement and decreased for avoidance movement compared with the default case of no chloroplast movement at high light intensities. Leakiness increased in both chloroplast movement scenarios due to the imbalance in energy production and demand in mesophyll and bundle sheath cells. These results suggest the need to design strategies for coordinated increases in electron transport and Rubisco activities for an efficient CO2 concentrating mechanism at very high light intensities.

The effect of drought on plant water use efficiency of nine NAD-ME and nine NADP-ME Australian C4 grasses

Publisher: CSIRO Publishing

Date: 2002

DOI: 10.1071/FP02056

Abstract: We investigated the response to drought of nine NAD–malic enzyme (NAD–ME) and nine NADP–malic enzyme (NADP–ME) C4 grasses. Species were grown from seeds in potted soil in a glasshouse. Seedlings were either watered regularly or exposed to two successive drying cycles of 8–10 d each, after which plants were harvested. Under well-watered conditions, average water use efficiency (WUE dry mass gain per unit water transpired) was similar for NAD–ME and NADP–ME C4 grasses, and ranged between 6.0 and 8.7 g dry mass kg–1 H2O. Drought enhanced WUE of most species, but to a significantly greater extent in NAD–ME (1.20-fold) than NADP–ME (1.11-fold) grasses. Inhibition of dry matter accumulation (average of 12%) and shoot elongation under drought was similar among the C4 grasses. Leaf dry matter carbon (δ13C) and oxygen (δ18O) isotope compositions were significantly different between the two C4 subtypes. Leaf δ13C averaged –13.3 and –12.2, and leaf δ18O averaged 26.0 and 26.9 in well-watered NAD–ME and NADP–ME grasses, respectively. Drought significantly reduced leaf δ13C in most C4 grasses by an average 0.5. Leaf δ18O was not significantly affected by drought, indicating that leaf δ18O does not reflect drought-induced changes in leaf transpiration of C4 grasses. In the experiment reported here, NAD–ME grasses increased their WUE under drought to a greater extent than their NADP–ME counterparts. Increased WUE of the C4 grasses under drought was primarily related to control of water loss relative to carbon gain at the leaf, rather than the plant, level.

Elevated [CO2] negatively impacts C4 photosynthesis under heat and water stress without penalizing biomass

Publisher: Oxford University Press (OUP)

Date: 17-02-2023

DOI: 10.1093/JXB/ERAD063

Abstract: Elevated [CO2] (eCO2) and water stress reduce leaf stomatal conductance (gs), which may affect leaf thermoregulation during heat waves (heat stress). Two sorghum lines, with different leaf width were grown in a glasshouse at a mean day temperature of 30 °C, under different [CO2] and watering levels, and subjected to heat stress (43 °C) for 6 d at the start of the reproductive stage. We measured leaf photosynthetic and stomatal responses to light transients before harvesting the plants. Photosynthesis at growth conditions (Agrowth) and biomass accumulation were enhanced by eCO2 under control conditions. Heat stress increased gs, especially in wider leaves, and reduced the time constant of stomatal opening (kopen) at ambient [CO2] but not eCO2. However, heat stress reduced photosynthesis under water stress and eCO2 due to increased leaf temperature and reduced evaporative cooling. eCO2 prevented the reduction of biomass under both water and heat stress, possibly due to improved plant and soil water status as a result of reduced gs. Our results suggest that the response of the C4 crop sorghum to future climate conditions depends on the trade-off between low gs needed for high water use efficiency and drought tolerance, and the high gs needed for improved thermoregulation and heat tolerance under an eCO2 future.

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.

On the role of ecological adaptation and geographic distribution in the response of trees to climate change

Publisher: Oxford University Press (OUP)

Date: 12-2011

DOI: 10.1093/TREEPHYS/TPR115

Linking photosynthesis and leaf N allocation under future elevated CO₂and climate warming inEucalyptus globulus

Publisher: Oxford University Press (OUP)

Date: 07-01-2017

DOI: 10.1093/JXB/ERW484

An energy-saving glasshouse film reduces seasonal, and cultivar dependent Capsicum yield due to light limited photosynthesis

Publisher: Elsevier BV

Date: 06-2023

DOI: 10.1016/J.AOAS.2023.04.001

Phosphorus deficiency inhibits growth in parallel with photosynthesis in a C3 (Panicum laxum) but not two C4 (P. coloratum and Cenchrus ciliaris) grasses

Publisher: CSIRO Publishing

Date: 2007

DOI: 10.1071/FP06253

Abstract: This study compared the growth and photosynthetic responses of one C3 (Panicum laxum L.) and two C4 grasses (Panicum coloratum L. and Cenchrus ciliaris L.) to changes in soil phosphorus (P) nutrition. Plants were grown in potted soil amended with six different concentrations of P. One week before harvest, leaf elongation and photosynthetic rates and the contents of carbohydrate, P and inorganic phosphate (Pi) were measured. Five weeks after germination, plants were harvested to estimate biomass accumulation. At each soil P supply, leaf P contents were lower in the C3 (0.6–2.6 mmol P m–2) than in the two C4 grasses (0.8–4.1 mmol P m–2), and Pi constituted ~40–65% of total leaf P. The P deficiency reduced leaf growth, tillering and plant dry mass to a similar extent in all three grasses. In contrast, P deficiency suppressed photosynthetic rates to a greater extent in the C3 (50%) than the C4 grasses (25%). The foliar contents of non-structural carbohydrates were affected only slightly by soil P supply in all three species. Leaf mass per area decreased at low P in the two C4 grasses only, and biomass partitioning changed little with soil P supply. The percentage changes in assimilation rates and plant dry mass were linearly related in the C3 but not the C4 plants. Thus, P deficiency reduced growth in parallel with reductions of photosynthesis in the C3 grass, and independently of photosynthesis in the two C4 grasses. We propose that this may be related to a greater Pi requirement of C4 relative to C3 photosynthesis. Photosynthetic P use efficiency was greater and increased more with P deficiency in the C4 relative to the C3 species. The opposite was observed for whole-plant P-use efficiency. Hence, the greater P-use efficiency of C4 photosynthesis was not transferred to the whole-plant level, mainly as a result of the larger and constant leaf P fraction in the two C4 grasses.

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

Publisher: Wiley

Date: 07-09-2010

DOI: 10.1111/J.1365-3040.2010.02172.X

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

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

Publisher: Wiley

Date: 25-01-2013

DOI: 10.1111/NPH.12104

Abstract: The rate of CO 2 assimilation by plants is directly influenced by the concentration of CO 2 in the atmosphere, c a . As an environmental variable, c a also has a unique global and historic significance. Although relatively stable and uniform in the short term, global c a has varied substantially on the timescale of thousands to millions of years, and currently is increasing at seemingly an unprecedented rate. This may exert profound impacts on both climate and plant function. Here we utilise extensive datasets and models to develop an integrated, multi‐scale assessment of the impact of changing c a on plant carbon dioxide uptake and water use. We find that, overall, the sensitivity of plants to rising or falling c a is qualitatively similar across all scales considered. It is characterised by an adaptive feedback response that tends to maintain 1 − c i / c a , the relative gradient for CO 2 diffusion into the leaf, relatively constant. This is achieved through predictable adjustments to stomatal anatomy and chloroplast biochemistry. Importantly, the long‐term response to changing c a can be described by simple equations rooted in the formulation of more commonly studied short‐term responses. Contents Summary 1077 I. Introduction 1078 II. Atmospheric CO 2 concentrations through time 1079 III. Plant sensitivity to CO 2 at geological timescales 1080 IV. Plant sensitivity to CO 2 over the last 200 yr 1081 V. Increased water‐use efficiency? 1084 VI. Simple formulation of stomatal conductance in land surface models for simulating long‐term CO 2 response 1087 VII. Conclusions 1088 Acknowledgements 1089 References 1089

Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition)

Publisher: Informa UK Limited

Date: 02-01-2016

DOI: 10.1080/15548627.2015.1100356

Temperature responses of Rubisco from Paniceae grasses provide opportunities for improving C3 photosynthesis

Publisher: Springer Science and Business Media LLC

Date: 28-11-2016

DOI: 10.1038/NPLANTS.2016.186

Abstract: Enhancing the catalytic properties of the CO

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

Publisher: CSIRO Publishing

Date: 2012

DOI: 10.1071/FP11238

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

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.

Western Sydney University - Hawkesbury Campus

Location: Australia

View Organisation

Boosting C4 Photosynthesis To Climate Proof Crop Yields

Start Date: 2023

End Date: 2025

Funder: Australian Research Council

Can Altered Sugar Sensing Improve Crop Productivity? This Project Aims At Genetically Manipulating Sugar Sensing Pathways In The Model C4 Grass Setaria Viridis, And At Replacing Sugar Sensors In The Model C3 Crop Oryza Sativa (rice) With Those From S

Start Date: 2021

End Date: 2023

Funder: Australian Research Council

Rubisco For All Climates: Unlocking The Enzyme's Structure-function Relations For More Efficient Photosynthesis

Start Date: 2012

End Date: 2014

Funder: Australian Research Council

ARC Centre Of Excellence For Translational Photosynthesis

Start Date: 2014

End Date: 2021

Funder: Australian Research Council

Will Trees Get Enough Nitrogen To Be Productive In Elevated Carbon Dioxide?

Start Date: 2016

End Date: 2018

Funder: Australian Research Council

The Effect Of Home Climate In A Rapidly Warming World On The Physiological Flexibility Of Forest Trees

Start Date: 2014

End Date: 2016

Funder: Australian Research Council

Discovery Projects - Grant ID: DP230100175

Start Date: 2023

End Date: 12-2025

Amount: $482,066.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP160102452

Start Date: 06-2016

End Date: 12-2019

Amount: $355,800.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP210102730

Start Date: 2021

End Date: 12-2024

Amount: $468,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP140103415

Start Date: 01-2014

End Date: 12-2017

Amount: $315,000.00

Funder: Australian Research Council

ARC Centres Of Excellence - Grant ID: CE140100015

Start Date: 2014

End Date: 05-2021

Amount: $22,000,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP120101603

Start Date: 02-2012

End Date: 12-2013

Amount: $330,000.00

Funder: Australian Research Council