High Stomatal Conductance in the Tomato Flacca Mutant Allows for Faster Photosynthetic Induction
Kaiser, Elias ; Morales, Alejandro ; Harbinson, Jeremy ; Heuvelink, Ep ; Marcelis, Leo F.M. - \ 2020
Frontiers in Plant Science 11 (2020). - ISSN 1664-462X
abscisic acid - air humidity - CO concentration - dynamic photosynthesis - fluctuating irradiance - stomatal conductance
Due to their slow movement and closure upon shade, partially closed stomata can be a substantial limitation to photosynthesis in variable light intensities. The abscisic acid deficient flacca mutant in tomato (Solanum lycopersicum) displays very high stomatal conductance (gs). We aimed to determine to what extent this substantially increased gs affects the rate of photosynthetic induction. Steady-state and dynamic photosynthesis characteristics were measured in flacca and wildtype leaves, by the use of simultaneous gas exchange and chlorophyll fluorometry. The steady-state response of photosynthesis to CO2, maximum quantum efficiency of photosystem II photochemistry (Fv/Fm), as well as mesophyll conductance to CO2 diffusion were not significantly different between genotypes, suggesting similar photosynthetic biochemistry, photoprotective capacity, and internal CO2 permeability. When leaves adapted to shade (50 µmol m−2 s−1) at 400 µbar CO2 partial pressure and high humidity (7 mbar leaf-to-air vapour pressure deficit, VPD) were exposed to high irradiance (1500 µmol m−2 s−1), photosynthetic induction was faster in flacca compared to wildtype leaves, and this was attributable to high initial gs in flacca (~0.6 mol m−2 s−1): in flacca, the times to reach 50 (t50) and 90% (t90) of full photosynthetic induction were 91 and 46% of wildtype values, respectively. Low humidity (15 mbar VPD) reduced gs and slowed down photosynthetic induction in the wildtype, while no change was observed in flacca; under low humidity, t50 was 63% and t90 was 36% of wildtype levels in flacca. Photosynthetic induction in low CO2 partial pressure (200 µbar) increased gs in the wildtype (but not in flacca), and revealed no differences in the rate of photosynthetic induction between genotypes. Effects of higher gs in flacca were also visible in transients of photosystem II operating efficiency and non-photochemical quenching. Our results show that at ambient CO2 partial pressure, wildtype gs is a substantial limitation to the rate of photosynthetic induction, which flacca overcomes by keeping its stomata open at all times, and it does so at the cost of reduced water use efficiency.
Salt stress and fluctuating light have separate effects on photosynthetic acclimation, but interactively affect biomass
Zhang, Yuqi ; Kaiser, Elias ; Marcelis, Leo F.M. ; Yang, Qichang ; Li, Tao - \ 2020
Plant, Cell & Environment 43 (2020)9. - ISSN 0140-7791 - p. 2192 - 2206.
fluctuating light - light acclimation - photosynthesis - salt stress - stomatal conductance - tomato
In nature, soil salinity and fluctuating light (FL) often occur concomitantly. However, it is unknown whether salt stress interacts with FL on leaf photosynthesis, architecture, biochemistry, pigmentation, mineral concentrations, as well as whole-plant biomass. To elucidate this, tomato (Solanum lycopersicum) seedlings were grown under constant light (C, 200 μmol m−2 s−1) or FL (5–650 μmol m−2 s−1), in combination with no (0 mM NaCl) or moderate (80 mM NaCl) salinity, for 14 days, at identical photoperiods and daily light integrals. FL and salt stress had separate effects on leaf anatomy, biochemistry and photosynthetic capacity: FL reduced leaf thickness as well as nitrogen, chlorophyll and carotenoid contents per unit leaf area, but rarely affected steady-state and dynamic photosynthetic properties along with abundance of key proteins in the electron transport chain. Salt stress, meanwhile, mainly disorganized chloroplast grana stacking, reduced stomatal density, size and aperture as well as photosynthetic capacity. Plant biomass was affected interactively by light regime and salt stress: FL reduced biomass in salt stressed plants by 17%, but it did not affect biomass of non-stressed plants. Our results stress the importance of considering FL when inferring effects of salt-stress on photosynthesis and productivity under fluctuating light intensities.
The acclimation of leaf photosynthesis of wheat and rice to seasonal temperature changes in T-FACE environments
Cai, Chuang ; Li, Gang ; Di, Lijun ; Ding, Yunjie ; Fu, Lin ; Guo, Xuanhe ; Struik, Paul C. ; Pan, Genxing ; Li, Haozheng ; Chen, Weiping ; Luo, Weihong ; Yin, Xinyou - \ 2020
Global Change Biology 26 (2020)2. - ISSN 1354-1013 - p. 539 - 556.
climate change - free-air CO enrichment - growth temperature - leaf nitrogen content - Oryza sativa L. - photosynthesis model - stomatal conductance - Triticum aestivum L.
Crops show considerable capacity to adjust their photosynthetic characteristics to seasonal changes in temperature. However, how photosynthesis acclimates to changes in seasonal temperature under future climate conditions has not been revealed. We measured leaf photosynthesis (An) of wheat (Triticum aestivum L.) and rice (Oryza sativa L.) grown under four combinations of two levels of CO2 (ambient and enriched up to 500 µmol/mol) and two levels of canopy temperature (ambient and increased by 1.5–2.0°C) in temperature by free-air CO2 enrichment (T-FACE) systems. Parameters of a biochemical C3-photosynthesis model and of a stomatal conductance (gs) model were estimated for the four conditions and for several crop stages. Some biochemical parameters related to electron transport and most gs parameters showed acclimation to seasonal growth temperature in both crops. The acclimation response did not differ much between wheat and rice, nor among the four treatments of the T-FACE systems, when the difference in the seasonal growth temperature was accounted for. The relationships between biochemical parameters and leaf nitrogen content were consistent across leaf ranks, developmental stages, and treatment conditions. The acclimation had a strong impact on gs model parameters: when parameter values of a particular stage were used, the model failed to correctly estimate gs values of other stages. Further analysis using the coupled gs–biochemical photosynthesis model showed that ignoring the acclimation effect did not result in critical errors in estimating leaf photosynthesis under future climate, as long as parameter values were measured or derived from data obtained before flowering.
Stomatal conductance, mesophyll conductance, and trans piration efficiency in relation to leaf anatomy in rice and wheat genotypes under drought
Ouyang, Wenjing ; Struik, Paul C. ; Yin, Xinyou ; Yang, Jianchang - \ 2017
Journal of Experimental Botany 68 (2017)18. - ISSN 0022-0957 - p. 5191 - 5205.
Drought - leaf anatomy - mesophyll conductance - rice - stomatal conductance - transpiration efficiency - wheat
Increasing leaf transpiration efficiency (TE) may provide leads for growing rice like dryland cereals such as wheat (Triticum aestivum). To explore avenues for improving TE in rice, variations in stomatal conductance (g s) and mesophyll conductance (g m) and their anatomical determinants were evaluated in two cultivars from each of lowland, aerobic, and upland groups of Oryza sativa, one cultivar of O. glaberrima, and two cultivars of T. aestivum, under three water regimes. The TE of upland rice, O. glaberrima, and wheat was more responsive to the g m /g s ratio than that of lowland and aerobic rice. Overall, the explanatory power of the particular anatomical trait varied among species. Low stomatal density mostly explained the low g s in drought-tolerant rice, whereas rice genotypes with smaller stomata generally responded more strongly to drought. Compared with rice, wheat had a higher g m, which was associated with thicker mesophyll tissue, mesophyll and chloroplasts more exposed to intercellular spaces, and thinner cell walls. Upland rice, O. glaberrima, and wheat cultivars minimized the decrease in g m under drought by maintaining high ratios of chloroplasts to exposed mesophyll cell walls. Rice TE could be improved by increasing the g m /g s ratio via modifying anatomical traits.
Forcing variables in simulation of transpiration of water stressed plants determined by principal component analysis
Durigon, Angelica ; Lier, Quirijn De Jong Van ; Metselaar, Klaas - \ 2016
International Agrophysics 30 (2016)4. - ISSN 0236-8722 - p. 431 - 445.
Ags model - common bean - net CO2 assimilation rate - stomatal conductance
To date, measuring plant transpiration at canopy scale is laborious and its estimation by numerical modelling can be used to assess high time frequency data. When using the model by Jacobs (1994) to simulate transpiration of water stressed plants it needs to be reparametrized. We compare the importance of model variables affecting simulated transpiration of water stressed plants. A systematic literature review was performed to recover existing parameterizations to be tested in the model. Data from a field experiment with common bean under full and deficit irrigation were used to correlate estimations to forcing variables applying principal component analysis. New parameterizations resulted in a moderate reduction of prediction errors and in an increase in model performance. Ags model was sensitive to changes in the mesophyll conductance and leaf angle distribution parameterizations, allowing model improvement. Simulated transpiration could be separated in temporal components. Daily, afternoon depression and long-term components for the fully irrigated treatment were more related to atmospheric forcing variables (specific humidity deficit between stomata and air, relative air humidity and canopy temperature). Daily and afternoon depression components for the deficit-irrigated treatment were related to both atmospheric and soil dryness, and long-term component was related to soil dryness.
Ecological relevance of strigolactones in nutrient uptake and other abiotic stresses, and in plant-microbe interactions below ground
Andreo Jimenez, B. ; Ruyter-Spira, C.P. ; Bouwmeester, H.J. ; Lopez-Raez, J.A. - \ 2015
Plant and Soil 394 (2015)1. - ISSN 0032-079X - p. 1 - 19.
arbuscular mycorrhizal fungi - carotenoid cleavage dioxygenases - root-system architecture - phosphate starvation - medicago-truncatula - drought stress - abscisic-acid - analog gr24 - stomatal conductance - rhizobial infection
Background Plants are exposed to ever changing and often unfavourable environmental conditions, which cause both abiotic and biotic stresses. They have evolved sophisticated mechanisms to flexibly adapt themselves to these stress conditions. To achieve such adaptation, they need to control and coordinate physiological, developmental and defence responses. These responses are regulated through a complex network of interconnected signalling pathways, in which plant hormones play a key role. Strigolactones (SLs) are multifunctional molecules recently classified as a new class of phytohormones, playing a key role as modulators of the coordinated plant development in response to nutrient deficient conditions, especially phosphorus shortage. Belowground, besides regulating root architecture, they also act as molecular cues that help plants to communicate with their environment. Scope This review discusses current knowledge on the different roles of SLs below-ground, paying special attention to their involvement in phosphorus uptake by the plant by regulating root architecture and the establishment of mutualistic symbiosis with arbuscular mycorrhizal fungi. Their involvement in plant responses to other abiotic stresses such as drought and salinity, as well as in other plant-(micro)organisms interactions such as nodulation and root parasitic plants are also highlighted. Finally, the agronomical implications of SLs below-ground and their potential use in sustainable agriculture are addressed. Conclusions Experimental evidence illustrates the biological and ecological importance of SLs in the rhizosphere. Their multifunctional nature opens up a wide range of possibilities for potential applications in agriculture. However, a more in-depth understanding on the SL functioning/signalling mechanisms is required to allow us to exploit their full potential.
Tree growth variation in the tropical forest: understanding effects of temperature, rainfall and CO2
Schippers, P. ; Sterck, F.J. ; Vlam, M. ; Zuidema, P.A. - \ 2015
Global Change Biology 21 (2015)7. - ISSN 1354-1013 - p. 2749 - 2761.
water-use efficiency - global vegetation models - woody-tissue respiration - leaf-area index - elevated co2 - thermal-acclimation - carbon sink - scaling relationships - stomatal conductance - primary productivity
Tropical forest responses to climatic variability have important consequences for global carbon cycling, but are poorly understood. As empirical, correlative studies cannot disentangle the interactive effects of climatic variables on tree growth, we used a tree growth model (IBTREE) to unravel the climate effects on different physiological pathways and in turn on stem growth variation. We parameterized the model for canopy trees of Toona ciliata (Meliaceae) from a Thai monsoon forest and compared predicted and measured variation from a tree-ring study over a 30-year period. We used historical climatic variation of minimum and maximum day temperature, precipitation and carbon dioxide (CO2) in different combinations to estimate the contribution of each climate factor in explaining the inter-annual variation in stem growth. Running the model with only variation in maximum temperature and rainfall yielded stem growth patterns that explained almost 70% of the observed inter-annual variation in stem growth. Our results show that maximum temperature had a strong negative effect on the stem growth by increasing respiration, reducing stomatal conductance and thus mitigating a higher transpiration demand, and – to a lesser extent – by directly reducing photosynthesis. Although stem growth was rather weakly sensitive to rain, stem growth variation responded strongly and positively to rainfall variation owing to the strong inter-annual fluctuations in rainfall. Minimum temperature and atmospheric CO2 concentration did not significantly contribute to explaining the inter-annual variation in stem growth. Our innovative approach – combining a simulation model with historical data on tree-ring growth and climate – allowed disentangling the effects of strongly correlated climate variables on growth through different physiological pathways. Similar studies on different species and in different forest types are needed to further improve our understanding of the sensitivity of tropical tree growth to climatic variability and change.
Joint control of terrestrial gross primary productivity by plant phenology and physiology
Xia, J. ; Niu, S. ; Ciais, P. ; Janssens, I.A. ; Chen, J. ; Ammann, C. ; Arain, A. ; Blanken, P.D. ; Cescatti, A. ; Moors, E.J. - \ 2015
Proceedings of the National Academy of Sciences of the United States of America 112 (2015)9. - ISSN 0027-8424 - p. 2788 - 2793.
climate-change - chlorophyll fluorescence - ecosystem productivity - vegetation phenology - stomatal conductance - forest phenology - carbon uptake - models - photosynthesis - variability
Terrestrial gross primary productivity (GPP) varies greatly over time and space. A better understanding of this variability is necessary for more accurate predictions of the future climate–carbon cycle feedback. Recent studies have suggested that variability in GPP is driven by a broad range of biotic and abiotic factors operating mainly through changes in vegetation phenology and physiological processes. However, it is still unclear how plant phenology and physiology can be integrated to explain the spatiotemporal variability of terrestrial GPP. Based on analyses of eddy–covariance and satellite-derived data, we decomposed annual terrestrial GPP into the length of the CO2 uptake period (CUP) and the seasonal maximal capacity of CO2 uptake (GPPmax). The product of CUP and GPPmax explained >90% of the temporal GPP variability in most areas of North America during 2000–2010 and the spatial GPP variation among globally distributed eddy flux tower sites. It also explained GPP response to the European heatwave in 2003 (r2 = 0.90) and GPP recovery after a fire disturbance in South Dakota (r2 = 0.88). Additional analysis of the eddy–covariance flux data shows that the interbiome variation in annual GPP is better explained by that in GPPmax than CUP. These findings indicate that terrestrial GPP is jointly controlled by ecosystem-level plant phenology and photosynthetic capacity, and greater understanding of GPPmax and CUP responses to environmental and biological variations will, thus, improve predictions of GPP over time and space.
Two perspectives on the coupled carbon, water and energy exchange in the planetary boundary layer
Combe, M. ; Vilà-Guerau De Arellano, J. ; Ouwersloot, H.G. ; Jacobs, C.M.J. ; Peters, W. - \ 2015
Biogeosciences 12 (2015). - ISSN 1726-4170 - p. 103 - 123.
ensemble kalman filter - land-surface model - leaf-area index - soil-moisture - use efficiency - climate-change - crop model - stomatal conductance - data assimilation - plant geography
Understanding the interactions between the land surface and the atmosphere is key to modelling boundary-layer meteorology and cloud formation, as well as carbon cycling and crop yield. In this study we explore these interactions in the exchange of water, heat and CO2 in a cropland–atmosphere system at the diurnal and local scale. To that end, we couple an atmospheric mixed-layer model (MXL) to two land-surface schemes developed from two different perspectives: while one land-surface scheme (A-gs) simulates vegetation from an atmospheric point of view, the other (GECROS) simulates vegetation from a carbon-storage point of view. We calculate surface fluxes of heat, moisture and carbon, as well as the resulting atmospheric state and boundary-layer dynamics, over a maize field in the Netherlands, on a day for which we have a rich set of observations available. Particular emphasis is placed on understanding the role of upper-atmosphere conditions like subsidence in comparison to the role of surface forcings like soil moisture. We show that the atmospheric-oriented model (MXL-A-gs) outperforms the carbon storage-oriented model (MXL-GECROS) on this diurnal scale. We find this performance is partly due to the difference of scales at which the models were made to run. Most importantly, this performance strongly depends on the sensitivity of the modelled stomatal conductance to water stress, which is implemented differently in each model. This sensitivity also influences the magnitude of the surface fluxes of CO2, water and heat (surface control) and subsequently impacts the boundary-layer growth and entrainment fluxes (upper atmosphere control), which alter the atmospheric state. These findings suggest that observed CO2 mole fractions in the boundary layer can reflect strong influences of both the surface and upper-atmosphere conditions, and the interpretation of CO2 mole fraction variations depends on the assumed land-surface coupling. We illustrate this with a sensitivity analysis where high subsidence and soil moisture depletion, typical for periods of drought, have competing and opposite effects on the boundary-layer height h. The resulting net decrease in h induces a change of 12 ppm in the late-afternoon CO2 mole fraction. Also, the effect of such high subsidence and soil moisture depletion on the surface Bowen ratio are of the same magnitude. Thus, correctly including such two-way land-surface interactions on the diurnal scale can potentially improve our understanding and interpretation of observed variations in atmospheric CO2, as well as improve crop yield forecasts by better describing the water loss and carbon gain.
Mechanisms of water supply and vegetation demand govern the seasonality and magnitude of evapotranspiration in Amazonia and Cerrado
Christoffersen, B.O. ; Restrepo-Coupe, N. ; Arain, M.A. ; Baker, I.T. ; Cestaro, B.P. ; Ciais, P. ; Fisher, J.B. ; Galbraith, D. ; Guan, X. ; Hurk, B. van den; Kruijt, B. - \ 2014
Agricultural and Forest Meteorology 191 (2014). - ISSN 0168-1923 - p. 33 - 50.
land-surface scheme - environment simulator jules - carbon-cycle feedbacks - stomatal conductance - regional evapotranspiration - atmosphere interactions - model description - biosphere model - boundary-layer - climate model
Evapotranspiration (E) in the Amazon connects forest function and regional climate via its role in precipitation recycling However, the mechanisms regulating water supply to vegetation and its demand for water remain poorly understood, especially during periods of seasonal water deficits In this study, we address two main questions: First, how do mechanisms of water supply (indicated by rooting depth and groundwater) and vegetation water demand (indicated by stomatal conductance and intrinsic water use efficiency) control evapotranspiration (E) along broad gradients of climate and vegetation from equatorial Amazonia to Cerrado, and second, how do these inferred mechanisms of supply and demand compare to those employed by a suite of ecosystem models? We used a network of eddy covariance towers in Brazil coupled with ancillary measurements to address these questions With respect to the magnitude and seasonality of E, models have much improved in equatorial tropical forests by eliminating most dry season water limitation, diverge in performance in transitional forests where seasonal water deficits are greater, and mostly capture the observed seasonal depressions in E at Cerrado However, many models depended universally on either deep roots or groundwater to mitigate dry season water deficits, the relative importance of which we found does not vary as a simple function of climate or vegetation In addition, canopy stomatal conductance (gs) regulates dry season vegetation demand for water at all except the wettest sites even as the seasonal cycle of E follows that of net radiation In contrast, some models simulated no seasonality in gs, even while matching the observed seasonal cycle of E. We suggest that canopy dynamics mediated by leaf phenology may play a significant role in such seasonality, a process poorly represented in models Model bias in gs and E, in turn, was related to biases arising from the simulated light response (gross primary productivity, GPP) or the intrinsic water use efficiency of photosynthesis (iWUE). We identified deficiencies in models which would not otherwise be apparent based on a simple comparison of simulated and observed rates of E. While some deficiencies can be remedied by parameter tuning, in most models they highlight the need for continued process development of belowground hydrology and in particular, the biological processes of root dynamics and leaf phenology, which via their controls on E, mediate vegetation-climate feedbacks in the tropics.
Terrestrial cycling of (CO2)-C-13 by photosynthesis, respiration, and biomass burning in SiBCASA
Velde, I.R. van der; Miller, J.B. ; Schaefer, K. ; Werf, G.R. van der; Krol, M.C. ; Peters, W. - \ 2014
Biogeosciences 11 (2014). - ISSN 1726-4170 - p. 6553 - 6571.
carbon-isotope discrimination - surface parameterization sib2 - ecosystem respiration - interannual variability - biophysical parameters - stomatal conductance - co2 assimilation - atmospheric gcms - global fields - dioxide
We present an enhanced version of the SiBCASA terrestrial biosphere model that is extended with (a) biomass burning emissions from the SiBCASA carbon pools using remotely sensed burned area from the Global Fire Emissions Database (GFED), (b) an isotopic discrimination scheme that calculates 13C signatures of photosynthesis and autotrophic respiration, and (c) a separate set of 13C pools to carry isotope ratios into heterotrophic respiration. We quantify in this study the terrestrial exchange of CO2 and 13CO2 as a function of environmental changes in humidity and biomass burning. The implementation of biomass burning yields similar fluxes as CASA-GFED both in magnitude and spatial patterns. The implementation of isotope exchange gives a global mean discrimination value of 15.2‰, ranges between 4 and 20‰ depending on the photosynthetic pathway in the plant, and compares favorably (annually and seasonally) with other published values. Similarly, the isotopic disequilibrium is similar to other studies that include a small effect of biomass burning as it shortens the turnover of carbon. In comparison to measurements, a newly modified starch/sugar storage pool propagates the isotopic discrimination anomalies to respiration much better. In addition, the amplitude of the drought response by SiBCASA is lower than suggested by the measured isotope ratios. We show that a slight increase in the stomatal closure for large vapor pressure deficit would amplify the respired isotope ratio variability. Our study highlights the importance of isotope ratio observations of 13C to assess and improve biochemical models like SiBCASA, especially with regard to the allocation and turnover of carbon and the responses to drought.
Increased water-use efficiency does not lead to enhanced tree growth under xeric and mesic conditions
Lévesque, M. ; Siegwolf, R. ; Saurer, M. ; Eilmann, B. ; Rigling, A. - \ 2014
New Phytologist 203 (2014)1. - ISSN 0028-646X - p. 94 - 109.
carbon-isotope discrimination - scots pine - atmospheric co2 - climate-change - conceptual-model - stomatal conductance - c-13/c-12 variations - forest ecosystems - drought response - oxygen isotopes
Higher atmospheric CO2 concentrations (ca ) can under certain conditions increase tree growth by enhancing photosynthesis, resulting in an increase of intrinsic water-use efficiency (i WUE) in trees. However, the magnitude of these effects and their interactions with changing climatic conditions are still poorly understood under xeric and mesic conditions. We combined radial growth analysis with intra- and interannual d(13) C and d(18) O measurements to investigate growth and physiological responses of Larix decidua, Picea abies, Pinus sylvestris, Pinus nigra and Pseudotsuga menziesii in relation to rising ca and changing climate at a xeric site in the dry inner Alps and at a mesic site in the Swiss lowlands. i WUE increased significantly over the last 50 yr by 8-29% and varied depending on species, site water availability, and seasons. Regardless of species and increased i WUE, radial growth has significantly declined under xeric conditions, whereas growth has not increased as expected under mesic conditions. Overall, drought-induced stomatal closure has reduced transpiration at the cost of reduced carbon uptake and growth. Our results indicate that, even under mesic conditions, the temperature-induced drought stress has overridden the potential CO2 'fertilization' on tree growth, hence challenging today's predictions of improved forest productivity of temperate forests
How light competition between plants affects their response to climate change
Loon, M.P. van; Schieving, F. ; Rietkerk, M. ; Dekker, S.C. ; Sterck, F.J. ; Anten, N.P.R. - \ 2014
New Phytologist 203 (2014)4. - ISSN 0028-646X - p. 1253 - 1265.
leaf-area index - co2 enrichment face - canopy carbon gain - elevated co2 - atmospheric co2 - stomatal conductance - terrestrial ecosystems - nitrogen availability - global change - gas-exchange
How plants respond to climate change is of major concern, as plants will strongly impact future ecosystem functioning, food production and climate. Here, we investigated how vegetation structure and functioning may be influenced by predicted increases in annual temperatures and atmospheric CO2 concentration, and modeled the extent to which local plant–plant interactions may modify these effects. A canopy model was developed, which calculates photosynthesis as a function of light, nitrogen, temperature, CO2 and water availability, and considers different degrees of light competition between neighboring plants through canopy mixing; soybean (Glycine max) was used as a reference system. The model predicts increased net photosynthesis and reduced stomatal conductance and transpiration under atmospheric CO2 increase. When CO2 elevation is combined with warming, photosynthesis is increased more, but transpiration is reduced less. Intriguingly, when competition is considered, the optimal response shifts to producing larger leaf areas, but with lower stomatal conductance and associated vegetation transpiration than when competition is not considered. Furthermore, only when competition is considered are the predicted effects of elevated CO2 on leaf area index (LAI) well within the range of observed effects obtained by Free air CO2 enrichment (FACE) experiments. Together, our results illustrate how competition between plants may modify vegetation responses to climate change.
Improving ecophysiological simulation models to predict the impact of elevated atmospheric CO2 concentration on crop productivity
Yin, X. - \ 2013
Annals of Botany 112 (2013)3. - ISSN 0305-7364 - p. 465 - 475.
open-top chambers - leaf-area index - carbon-dioxide enrichment - climate-change impacts - open-air conditions - c-3 plants - photosynthetic capacity - stomatal conductance - winter-wheat - maintenance respiration
Background - Process-based ecophysiological crop models are pivotal in assessing responses of crop productivity and designing strategies of adaptation to climate change. Most existing crop models generally over-estimate the effect of elevated atmospheric [CO2], despite decades of experimental research on crop growth response to [CO2]. Analysis - A review of the literature indicates that the quantitative relationships for a number of traits, once expressed as a function of internal plant nitrogen status, are altered little by the elevated [CO2]. A model incorporating these nitrogen-based functional relationships and mechanisms simulated photosynthetic acclimation to elevated [CO2], thereby reducing the chance of over-estimating crop response to [CO2]. Robust crop models to have small parameterization requirements and yet generate phenotypic plasticity under changing environmental conditions need to capture the carbon–nitrogen interactions during crop growth. Conclusions - The performance of the improved models depends little on the type of the experimental facilities used to obtain data for parameterization, and allows accurate projections of the impact of elevated [CO2] and other climatic variables on crop productivity.
Biosphere model simulations of interannual variability in terrestrial 13C/12C exchange.
Velde, I.R. van der; Miller, J.B. ; Schaefer, K. ; Masarie, K.A. ; Denning, S. ; White, J.W.C. ; Krol, M.C. ; Peters, W. ; Tans, P.P. - \ 2013
Global Biogeochemical Cycles 27 (2013)3. - ISSN 0886-6236 - p. 637 - 649.
carbon-isotope discrimination - ocean co2 sink - stomatal conductance - c-13 discrimination - atmospheric co2 - cycle - climate - fires - photosynthesis - assimilation
Previous studies suggest that a large part of the variability in the atmospheric ratio of (CO2)-C-13/(12)CO(2)originates from carbon exchange with the terrestrial biosphere rather than with the oceans. Since this variability is used to quantitatively partition the total carbon sink, we here investigate the contribution of interannual variability (IAV) in biospheric exchange to the observed atmospheric C-13 variations. We use the Simple Biosphere - Carnegie-Ames-Stanford Approach biogeochemical model, including a detailed isotopic fractionation scheme, separate C-12 and C-13 biogeochemical pools, and satellite-observed fire disturbances. This model of (CO2)-C-12 and (CO2)-C-13 thus also produces return fluxes of (13)CO(2)from its differently aged pools, contributing to the so-called disequilibrium flux. Our simulated terrestrial C-13 budget closely resembles previously published model results for plant discrimination and disequilibrium fluxes and similarly suggests that variations in C-3 discrimination and year-to-year variations in C(3)and C-4 productivity are the main drivers of their IAV. But the year-to-year variability in the isotopic disequilibrium flux is much lower (1 sigma=1.5PgCyr(-1)) than required (12.5PgCyr(-1)) to match atmospheric observations, under the common assumption of low variability in net ocean CO2 fluxes. This contrasts with earlier published results. It is currently unclear how to increase IAV in these drivers suggesting that SiBCASA still misses processes that enhance variability in plant discrimination and relative C-3/C(4)productivity. Alternatively, C-13 budget terms other than terrestrial disequilibrium fluxes, including possibly the atmospheric growth rate, must have significantly different IAV in order to close the atmospheric C-13 budget on a year-to-year basis.
Natural land carbon dioxide exchanges in the ECMWF integrated forecasting system: Implementation and offline validation
Boussetta, S. ; Balsamo, G. ; Beljaars, A.C.M. ; Panareda, A.A. ; Calvet, J.C. ; Jacobs, C.M.J. ; Hurk, B.J.J.M. van den; Viterbo, P. ; Lafont, S. ; Dutra, E. - \ 2013
Journal of Geophysical Research: Atmospheres 118 (2013)12. - ISSN 2169-897X - p. 5923 - 5946.
global vegetation model - data assimilation system - net ecosystem exchange - era-interim reanalysis - isba-a-gs - interannual variability - co2 exchange - stomatal conductance - southwestern france - soil respiration
The European Centre for Medium-Range Weather Forecasts land surface model has been extended to include a carbon dioxide module. This relates photosynthesis to radiation, atmospheric carbon dioxide (CO2) concentration, soil moisture, and temperature. Furthermore, it has the option of deriving a canopy resistance from photosynthesis and providing it as a stomatal control to the transpiration formulation. Ecosystem respiration is based on empirical relations dependent on temperature, soil moisture, snow depth, and land use. The CO2 model is designed for the numerical weather prediction (NWP) environment where it benefits from good quality meteorological input (i.e., radiation, temperature, and soil moisture). This paper describes the CO2 model formulation and the way it is optimized making use of off-line simulations for a full year of tower observations at 34 sites. The model is then evaluated against the same observations for a different year. A correlation coefficient of 0.65 is obtained between model simulations and observations based on 10 day averaged CO2 fluxes. For sensible and latent heat fluxes there is a correlation coefficient of 0.80. To study the impact on atmospheric CO2, coupled integrations are performed for the 2003 to 2008 period. The global atmospheric growth is well reproduced. The simulated interannual variability is shown to reproduce the observationally based estimates with a correlation coefficient of 0.70. The main conclusions are (i) the simple carbon dioxide model is highly suitable for the numerical weather prediction environment where environmental factors are controlled by data assimilation, (ii) the use of a carbon dioxide model for stomatal control has a positive impact on evapotranspiration, and (iii) even using a climatological leaf area index, the interannual variability of the global atmospheric CO2 budget is well reproduced due to the interannual variability in the meteorological forcing (i.e., radiation, precipitation, temperature, humidity, and soil moisture) despite the simplified or missing processes. This highlights the importance of meteorological forcing but also cautions the use of such a simple model for process attribution.
Pine and mistletoes: how to live with a leak in the water flow and storage system
Zweifel, R. ; Bangerter, S. ; Rigling, A. ; Sterck, F.J. - \ 2012
Journal of Experimental Botany 63 (2012)7. - ISSN 0022-0957 - p. 2565 - 2578.
album ssp austriacum - scots pine - drought stress - sylvestris l. - stomatal conductance - pubescent oak - rhone valley - carbon - mortality - xylem
The mistletoe, Viscum album, living on Scots pine (Pinus sylvestris) has been reported barely to regulate its transpiration and thus heavily to affect the gas exchange of its host. The extent of this mistletoe effect and its underlying mechanism has, so far, only been partially analysed. In this study, pine branches with different mistletoe infestation levels were investigated by sap flow gauges and analysed with a modelling approach to identify the mistletoe-induced stomatal regulation of pine and its consequences for the water and carbon balances of the tree. It was found that Viscum album barely regulates its stomata and that pines consequently compensate for the additional water loss of mistletoes by closing their own stomata. Despite the reduced stomatal aperture of the needles, the total water loss of branches with mistletoes increased. Furthermore, the increasingly closed stomata reduced carbon assimilation for the pine. Such a negative effect of the mistletoes on pine’s stomatal conductance and carbon gain was particularly strong during dry periods. Our study therefore suggests that mistletoe-induced stomatal closure is a successful mechanism against dying from hydraulic failure in the short term but increases the risk of carbon starvation in the long term. With the current conditions in Valais, Switzerland, a tree with more than about 10–20% of its total leaf area attributable to mistletoes is at the threshold of keeping a positive carbon balance. The currently increasing mistletoe abundance, due to increasing mean annual temperatures, is therefore accelerating the ongoing pine decline in many dry inner-Alpine valleys.
Leaf photosynthetic and morphological responses to elevated CO2 concentration and altered fruit number in the semi-closed greenhouse
Qian, T. ; Dieleman, J.A. ; Elings, A. ; Marcelis, L.F.M. - \ 2012
Scientia Horticulturae 145 (2012). - ISSN 0304-4238 - p. 1 - 9.
high atmospheric co2 - ribulose-1,5-bisphosphate carboxylation limitation - carbon-dioxide concentrations - dynamic simulation-model - dry-matter production - tomato plants - stomatal conductance - gas-exchange - closed greenhouse - whole-plant
Semi-closed greenhouses have been developed to reduce the energy consumption in horticulture. In these greenhouses, CO2 concentration is higher than in the conventional modern greenhouses due to the reduction of window ventilation. Photosynthetic and morphological acclimation to elevated CO2 has been found in many plant species with feedback inhibition being the main mechanism to explain this. The aim of this study was to investigate the occurrence of photosynthetic and morphological acclimation to elevated CO2 concentration in the semi-closed greenhouse. Our hypothesis was that photosynthetic and morphological acclimation to elevated CO2 concentration only occurred in plants with low sink strength. Experiments were carried out with tomato plants with varying fruit loads in a semi-closed greenhouse and a conventional modern greenhouse. Our results showed that photosynthetic acclimation to elevated CO2 concentration only occurred when the number of fruits was considerably reduced. Elevated CO2 as well as fruit removal reduced specific leaf area. Reduction in photosynthesis rate was associated with, but not caused by reduced stomatal conductance. The increase of dry matter production in the semi-closed greenhouse was mainly explained by a higher CO2 concentration compared to the open greenhouse. We suggested that elevated CO2 concentrations in the semi-closed greenhouse do not cause feedback inhibition in high producing crops, because the plants have sufficient sink organs (fruits) to utilise the extra assimilates
Estimation of photosynthesis parameters for a modified Farquhar–von Caemmerer–Berry model using simultaneous estimation method and nonlinear mixed effects model
Qian, T. ; Elings, A. ; Dieleman, J.A. ; Gort, G. ; Marcelis, L.F.M. - \ 2012
Environmental and Experimental Botany 82 (2012). - ISSN 0098-8472 - p. 66 - 73.
ribulose bisphosphate carboxylase - biochemically based model - light-response curve - co2 partial-pressure - h2o gas-exchange - mesophyll conductance - temperature response - stomatal conductance - seasonal-changes - carbon-dioxide
The aims of this paper was to modify the photosynthesis model of Farquhar, von Caemmerer and Berry (FvCB) to be able to predict light dependency of the carboxylation capacity (Vc) and to improve the prediction of temperature dependency of the maximum carboxylation capacity (Vcmax) and the maximum electron transport rate (Jmax). The FvCB model was modified by adding a sub-model for Ribulose-1,5-bisphosphate carboxylase (Rubisco) activation and validating the parameters for temperature dependency of Vcmax and Jmax. Values of parameters for temperature dependency of Vcmax and Jmax were validated and adjusted based on data of the photosynthesis response to temperature. Parameter estimation was based on measurements under a wide range of environmental conditions, providing parameters with broad validity. The simultaneous estimation method and the nonlinear mixed effects model were applied to ensure the accuracy of the parameter estimation. The FvCB parameters, Vcmax, Jmax, a (the efficiency of light energy conversion), ¿ (the curvature of light response of electron transport), and Rd (the non-photorespiratory CO2 release) were estimated and validated on a dataset from two other years. Observations and predictions matched well (R2 = 0.94). We conclude that incorporating a sub-model of Rubisco activation improved the FvCB model through predicting light dependency of carboxylation rate; and that estimating Vcmax, Jmax, a, ¿, and Rd requires data sets of both CO2 and light response curves.
Evaluation of diel patterns of relative changes in cell turgor of tomato plants using leaf patch clamp pressure probes
Lee, K.M. ; Driever, S.M. ; Heuvelink, E. ; Rüger, S. ; Zimmermann, U. ; Gelder, A. de; Marcelis, L.F.M. - \ 2012
Physiologia Plantarum 146 (2012)4. - ISSN 0031-9317 - p. 439 - 447.
water status - hydraulic conductance - stomatal conductance - dynamic changes - tree - irrigation - growth - leaves - stress - vulnerability
Relative changes in cell turgor of leaves of well-watered tomato plants were evaluated using the leaf patch clamp pressure probe (LPCP) under dynamic greenhouse climate conditions. Leaf patch clamp pressure changes, a measure for relative changes in cell turgor, were monitored at three different heights of transpiring and non-transpiring leaves of tomato plants on sunny and cloudy days simultaneously with whole plant water uptake. Clear diel patterns were observed for relative changes of cell turgor of both transpiring and non-transpiring leaves, which were stronger on sunny days than on cloudy days. A clear effect of canopy height was also observed. Non-transpiring leaves showed relative changes in cell turgor that closely followed plant water uptake throughout the day. However, in the afternoon the relative changes of cell turgor of the transpiring leaves displayed a delayed response in comparison to plant water uptake. Subsequent recovery of cell turgor loss of transpiring leaves during the following night appeared insufficient, as the pre-dawn turgescent state similar to the previous night was not attained