scholarly journals Modelling the climatic drivers determining photosynthesis and carbon allocation in evergreen Mediterranean forests using multiproxy long time series

2015 ◽  
Vol 12 (12) ◽  
pp. 3695-3712 ◽  
Author(s):  
G. Gea-Izquierdo ◽  
F. Guibal ◽  
R. Joffre ◽  
J. M. Ourcival ◽  
G. Simioni ◽  
...  
Keyword(s):  
Time Series ◽  
Water Stress ◽  
Stomatal Conductance ◽  
Water Use ◽  
Carbon Allocation ◽  
Climatic Variability ◽  
Mediterranean Forests ◽  
Climatic Drivers ◽  
Use Efficiency

Abstract. Climatic drivers limit several important physiological processes involved in ecosystem carbon dynamics including gross primary productivity (GPP) and carbon allocation in vegetation. Climatic variability limits these two processes differently. We developed an existing mechanistic model to analyse photosynthesis and variability in carbon allocation in two evergreen species at two Mediterranean forests. The model was calibrated using a combination of eddy covariance CO2 flux data, dendrochronological time series of secondary growth and forest inventory data. The model was modified to be climate explicit in the key processes addressing the acclimation of photosynthesis and the pattern of C allocation, particularly to water stress. It succeeded in fitting both the high- and the low-frequency response of stand GPP and carbon allocation to stem growth. This would support its capability to address both C-source and C-sink limitations. Simulations suggest a decrease in mean stomatal conductance in response to a recent enhancement in water stress and an increase in mean annual intrinsic water use efficiency (iWUE) in both species during the last 50 years. However, this was not translated into a parallel increase in ecosystem water use efficiency (WUE). The interannual variability in WUE closely followed that in iWUE at both sites. Nevertheless, long-term decadal variability in WUE followed the long-term decrease in annual GPP matching the local trend in annual precipitation observed since the late 1970s at one site. In contrast, at the site where long-term precipitation remained stable, GPP and WUE did not show a negative trend and the trees buffered the climatic variability. In our simulations these temporal changes were related to acclimation processes at the canopy level, including modifications in LAI and stomatal conductance, but also partly related to increasing [CO2] because the model includes biochemical equations where photosynthesis is directly linked to [CO2]. Long-term trends in GPP did not match those in growth, in agreement with the C-sink hypothesis. The model has great potential for use with abundant dendrochronological data and analyse forest performance under climate change. This would help to understand how different interfering environmental factors produce instability in the pattern of carbon allocation and, hence, the climatic signal expressed in tree rings.

scholarly journals Modelling the climatic drivers determining photosynthesis and carbon allocation in evergreen Mediterranean forests using multiproxy long time series

2015 ◽  
Vol 12 (3) ◽  
pp. 2745-2786
Author(s):  
G. Gea-Izquierdo ◽  
F. Guibal ◽  
R. Joffre ◽  
J. M. Ourcival ◽  
G. Simioni ◽  
...  
Keyword(s):  
Time Series ◽  
Water Use Efficiency ◽  
Water Use ◽  
Carbon Allocation ◽  
Climatic Variability ◽  
Mediterranean Forests ◽  
Intrinsic Water Use Efficiency ◽  
Climatic Drivers ◽  
Use Efficiency

Abstract. Climatic drivers limit several important physiological processes involved in ecosystem carbon dynamics including gross primary productivity (GPP) and carbon allocation in vegetation. Climatic variability limits these two processes differently. We developed an existing mechanistic model to analyse photosynthesis and variability in carbon allocation in two evergreen species at two Mediterranean forests. The model was calibrated using a combination of eddy covariance CO2 flux data, dendrochronological time series of secondary growth and forest inventory data. The model was modified to be climate explicit in the key processes addressing acclimation of photosynthesis and allocation. It succeeded to fit both the high- and the low-frequency response of stand GPP and carbon allocation to the stem. This would support its capability to address both carbon source and sink limitations. Simulations suggest a decrease in mean stomatal conductance in response to environmental changes and an increase in mean annual intrinsic water use efficiency (iWUE) in both species during the last 50 years. However, this was not translated on a parallel increase in ecosystem water use efficiency (WUE). A long-term decrease in annual GPP matched the local trend in precipitation since the 1970s observed in one site. In contrast, GPP did not show a negative trend and the trees buffered the climatic variability observed at the site where long-term precipitation remained stable. In our simulations these temporal changes would be partly related to increasing [CO2] because the model includes biochemical equations where photosynthesis is directly linked to [CO2]. Long-term trends in GPP did not match those in growth, in agreement with the C-sink hypothesis. There is a great potential to use the model with abundant dendrochronological data and analyse forest performance under climate change. This would help to understand how different interfering environmental factors produce instability in the climatic signal expressed in tree-rings.

Response of greenhouse-grown bell pepper (Capsicum annuum L.) to variable irrigation

2014 ◽  
Vol 94 (2) ◽  
pp. 303-310 ◽  
Author(s):  
Olanike Aladenola ◽  
Chandra Madramootoo
Keyword(s):  
Water Stress ◽  
Stomatal Conductance ◽  
Water Use Efficiency ◽  
Capsicum Annuum ◽  
Water Use ◽  
Irrigation Water ◽  
Bell Pepper ◽  
Marketable Yield ◽  
Capsicum Annuum L ◽  
Use Efficiency

Aladenola, O. and Madramootoo, C. 2014. Response of greenhouse-grown bell pepper (Capsicum annuum L.) to variable irrigation. Can. J. Plant Sci. 94: 303–310. In order to optimize water use in bell pepper production information about the appropriate irrigation water applications and agronomic and physiological response to mild and severe water stress is necessary. Different water applications were tested on yield, quality and water stress threshold of greenhouse-grown bell pepper (Capsicum annuum L.) cultivar Red Knight in 2011 and 2012 on the Macdonald Campus of McGill University, Ste Anne De Bellevue, QC. The study was carried out on a soil substrate in the greenhouse. Irrigation was scheduled with four treatments:120% (T1), 100% (T2), 80% (T3), and 40% (T4) replenishment of crop evapotranspiration in a completely randomized design. The highest marketable yield, water use efficiency and irrigation water use efficiency were obtained with T1 in both years. T1 received 20% more water than T2 to produce 23% more marketable yield than T2. Fruit total soluble solids content was highest in T4, and smallest in T1. The mean crop water stress index (CWSI) of the irrigation treatments ranged between 0.08 and 1.18. Leaf stomatal conductance of bell pepper was 75 to 80% lower in T4 than in T1. Regression obtained between stomatal conductance and CWSI resulted in a polynomial curve with coefficients of determination of 0.88 and 0.97 in 2011 and 2012, respectively. The result from this study indicate that the yield derived justifies the use of an extra quantity of water. Information from this study will help water regulators to make appropriate decision about water to be allocated for greenhouse production of bell pepper.

Stomatal and non-stomatal limitations of photosynthesis under water stress in field-grown grapevines

1999 ◽  
Vol 26 (5) ◽  
pp. 421 ◽  
Author(s):  
J. M. Escalona ◽  
J. Flexas ◽  
H. Medrano
Keyword(s):  
Water Stress ◽  
Stomatal Conductance ◽  
Relative Increase ◽  
Apparent Quantum Yield ◽  
Intrinsic Water Use Efficiency ◽  
Regulation Mechanisms ◽  
Use Efficiency ◽  
Alternative Processes ◽  
Stomatal Limitations

Long-term induced water stress in field-grown grapevine leads to a progressive decline of stomatal conductance, accompanied by a decrease in CO 2 assimilation (40%). The apparent quantum yield also decreases (59%), which may reflect a relative increase in alternative processes for electron consumption. There is also a shift to non-stomatal regulation, as judged from significant depletions (37%) in maximum photosynthesis rate at saturating CO 2 related to limited ribulose biphosphate (RuBP) regeneration, whereas small, non-significant effects are observed on carboxylation efficiency. A high correlation (87%) between photosynthesis and stomatal conductance is observed for all experimental data and declines in intercellular CO 2 concentration parallel reductions in stomatal conductance. The data show that field response of grapevines to increasing soil water deficit involves stomatal and non-stomatal effects but, due to gradually induced drought, regulation mechanisms able to adjust mesophyll capacity to the average CO 2 supply. The non-stomatal adjustment seems to be exerted mainly in metabolic pathways related with the RuBP regeneration. Contrasting characteristics were observed for both cultivars. Tempranillo exploited the non-stressful conditions successfully, whereas Manto Negro, responding to its reputation as more drought resistant, showed a higher intrinsic water use efficiency, particularly for low water availability. This advantage seems to be due to lower non-stomatal limitations.

scholarly journals IS ABSCISIC ACID INVOLVED IN THE DROUGHT RESPONSES OF BRAZILIAN GREEN DWARF COCONUT?

2009 ◽  
Vol 45 (2) ◽  
pp. 189-198 ◽  
Author(s):  
F. P. GOMES ◽  
M. A. OLIVA ◽  
M. S. MIELKE ◽  
A-A. F. DE ALMEIDA ◽  
H. G. LEITE ◽  
...  
Keyword(s):  
Abscisic Acid ◽  
Water Stress ◽  
Stomatal Conductance ◽  
Gas Exchange ◽  
Water Potential ◽  
Water Use ◽  
Severe Drought ◽  
Use Efficiency ◽  
Recovery Cycles ◽  
Mild Drought

SUMMARYAbscisic acid (ABA) accumulation in leaves of drought-stressed coconut palms and its involvement with stomatal regulation of gas exchange during and after stress were investigated. Two Brazilian Green Dwarf coconut ecotypes from hot/humid and hot/dry environments were submitted to three consecutive drying/recovery cycles under greenhouse conditions. ABA accumulated in leaflets before significant changes in pre-dawn leaflet water potential (ΨPD) and did not recover completely in the two ecotypes after 8 days of rewatering. Stomatal conductance was influenced by ABA under mild drought and by ΨPD under severe drought. There were no significant differences between the ecotypes for most variables measured. However, the ecotype from a hot/dry environment showed higher water use efficiency after repeated cycles of water stress.

Stomatal and non-stomatal limitations of photosynthesis under water stress in field-grown grapevines

2000 ◽  
Vol 27 (1) ◽  
pp. 87 ◽  
Author(s):  
J. M. Escalona ◽  
J. Flexas ◽  
H. Medrano
Keyword(s):  
Water Stress ◽  
Stomatal Conductance ◽  
Relative Increase ◽  
Apparent Quantum Yield ◽  
Intrinsic Water Use Efficiency ◽  
Regulation Mechanisms ◽  
Use Efficiency ◽  
Alternative Processes ◽  
Stomatal Limitations

Long-term induced water stress in field-grown grapevine leads to a progressive decline of stomatal conductance, accompanied by a decrease in CO 2 assimilation (40%). The apparent quantum yield also decreases (59%), which may reflect a relative increase in alternative processes for electron consumption. There is also a shift to non-stomatal regulation, as judged from significant depletions (37%) in maximum photosynthesis rate at saturating CO 2 related to limited ribulose biphosphate (RuBP) regeneration, whereas small, non-significant effects are observed on carboxylation efficiency. A high correlation (87%) between photosynthesis and stomatal conductance is observed for all experimental data and declines in intercellular CO 2 concentration parallel reductions in stomatal conductance. The data show that field response of grapevines to increasing soil water deficit involves stomatal and non-stomatal effects but, due to gradually induced drought, regulation mechanisms able to adjust mesophyll capacity to the average CO 2 supply. The non-stomatal adjustment seems to be exerted mainly in metabolic pathways related with the RuBP regeneration. Contrasting characteristics were observed for both cultivars. Tempranillo exploited the non-stressful conditions successfully, whereas Manto Negro, responding to its reputation as more drought resistant, showed a higher intrinsic water use efficiency, particularly for low water availability. This advantage seems to be due to lower non-stomatal limitations.

scholarly journals Induced Genetic Variations in Stomatal Density and Size of Rice Strongly Affect Water-Use Efficiency, Drought Tolerance, and Responses to Abiotic Stresses

2021 ◽  
Author(s):  
Mutiara K. Pitaloka ◽  
Robert S. Caine ◽  
Christopher Hepworth ◽  
Emily L. Harrison ◽  
Jen Sloan ◽  
...  
Keyword(s):  
Water Stress ◽  
Water Treatment ◽  
Water Use Efficiency ◽  
Water Use ◽  
Stomatal Density ◽  
The Other ◽  
Low Density ◽  
Stomata Density ◽  
Use Efficiency

Abstract BackgroundRice (Oryza sativa) is one of the world’s most important crops and is especially important in Asia. Because irrigated rice consumes about 34–43% of the total water used for irrigation globally, increasing drought and global temperature will increase the risk of rice crop loss. However, rice is among the least efficient crops in terms of water use, whereby most of the uptaken water is used for transpirational cooling via stomatal pores on the leaf blades and sheaths. To increase the water-use efficiency of rice, alterations in stomatal density and size may help to reduce transpiration and thereby increase water-use efficiency (WUE). ResultsWe identified four stomatal model lines—with either high-density (HD) or low-density (LD) stomata and small-sized (SS) or big-sized (BS) stomata—from the Mutant Core Collection (MCC) of 216 mutants. Gas exchange analysis revealed that the stomatal model lines have similar photosynthetic assimilation (A) and chlorophyll fluorescence. With increasing CO2 concentration, A of all stomatal model lines was observed to respond similarly at 100–600 ppm CO2, but beyond this point, SS was more responsive to increasing CO2 concentration than the other stomatal model lines. HD had higher stomatal conductance (gs) and gsmax than the other stomatal model lines. In response to a mild heat at 30 °C, both SS and LD had higher canopy temperature than HD, BS, and JHN-wt as a result of heat retention. All stomatal model lines are also similar in their rhythmic stomatal responses to ten-minute dark/light transition cycles, except that initial stomata closure in SS was more rapid than in BS. The stomatal model lines did not show any significant differences in the response to short-term water stress. Long-term water stress had less impact on leaf drying, Fv/Fm, grain yield, and harvest index in LD and SS. In the field, all stomatal model lines and JHN-wt had similar WUE in the sufficient-water treatment. LD had the highest WUE and biomass/plant than any stomatal model lines in the long-term restricted-water treatment. ConclusionsTaken together, our results suggest that induced alterations in stomata density and size influence rice WUE and the responses to drought and heat stresses, providing further understanding of the roles of stomata density and size in related processes. The low-density and small stomata lines have high potential as genetic donors for improving WUE and drought in climate-ready rice.

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