Phenotyping for Photosynthetic Traits Elizabete Carmo-Silva Michael E Salvucci Martin AJ Parry OPTICHINA 2nd Workshop, Barcelona, September 212
Why Photosynthesis? Photosynthetic assimilation of carbon is the primary determinant of crop biomass Increase Photosynthesis Increase Crop Yields Other interacting factors are important to fully exploit carbon gains (e.g., respiration, assimilate partitioning)
Cotton (US) Wheat (UK)
Meteorological Data 5 US 4 Tair (average) = 31.6 C PPT (total) = 6 mm 4 3 3 2 2 1 1 Precipitation (mm) Air Temperature ( C) MAC, US - 21 16 17 18 19 2 21 22 23 24 Day of Year 5 4 Tair (average) = 32.2 C PPT (total) = 12 mm 4 3 3 2 2 1 1 Precipitation (mm) Air Temperature ( C) MAC, US - 211 16 17 18 19 2 21 22 23 24 Day of Year Data Source: http://ag.arizona.edu/azmet/6.htm
Meteorological Data 5 UK 4 Tair (average) = 16.3 C PPT (total) = 2 mm 4 3 3 2 2 1 1 Precipitation (mm) Air Temperature ( C) RRes, UK - 21 16 17 18 19 2 21 22 23 24 Day of Year 5 4 Tair (average) = 15.2 C PPT (total) = 228 mm 4 3 3 2 2 1 1 Precipitation (mm) Air Temperature ( C) RRes, UK - 211 16 17 18 19 2 21 22 23 24 Day of Year Data Source: www.era.rothamsted.ac.uk
Meteorological Data 5 US 4 Tair (average) = 31.6 C PPT (total) = 6 mm 4 3 3 2 2 1 1 Precipitation (mm) Air Temperature ( C) MAC, US - 21 16 17 18 19 2 21 22 23 24 of Year Study Effects of Day Heat & Drought Stress 5 4 Tair (average) = 32.2 C PPT (total) = 12 mm 4 3 3 2 2 1 1 Precipitation (mm) Air Temperature ( C) MAC, US - 211 16 17 18 19 2 21 22 23 24 Day of Year Data Source: http://ag.arizona.edu/azmet/6.htm
Canopy Temperature Temperature ( C) 4 Early morning Late morning Early afternoon WW WL Air Tempt: - Early PM - Late AM 35 3 - Early AM 25 2 9 Evaporative cooling under WW conditions Heat & drought stress under WL conditions RWC (%) WW WL 85 8 75 7 65 Carmo-Silva et al. (212) Environ Exp Bot 83:1-11
Phenotyping Photosynthesis: Gas-exchange & Biochemistry WW: water to field-capacity (3-4 days a week) WL: one-half of WW irrigation Measurements taken 3 DAW (through the season)
Photosynthesis under Drought & Heat Stress Decreased stomatal conductance WW WL -1 3.6.4.2 2 1 Diffusional limitation. Limited photosynthesis 4 A ( mol m-2 s-1) -2-1 Ci ( mol mol ).8 gs (mol m s ) Lower intercellular [CO2] 3 2 1 Carmo-Silva et al. (212) Environ Exp Bot 83:1-11
Photosynthesis under Drought & Heat Stress WW WL.8-2 -1 gs (mol m s ) Rubisco activase activity (fraction of sites activated min-1) Decreased stomatal conductance.6.4.2..12 Activase inhibition.1.8.6.4.2. 2 3 35 4 Temperature ( C) Higher leaf temperature Carmo-Silva & Salvucci (211) Photosynth Res 18:143-155 4 3 2 Inactivation of Rubisco 1 Rubisco Activation (%) Tleaf ( C) 25 1 9 8 7 Metabolic limitation 6 5 Carmo-Silva et al. (212) Environ Exp Bot 83:1-11
Photosynthesis under Drought & Heat Stress Decreased stomatal conductance WW WL -2 3-1 -1 Ci ( mol mol ).8 gs (mol m s ) Lower intercellular [CO2].6.4.2 2 1 Diffusional limitation (Drought). Limited photosynthesis 3 2 Inactivation of Rubisco 1 Rubisco Activation (%) Tleaf ( C) 4 A ( mol m-2 s-1) 4 Higher leaf temperature 3 2 1 1 9 8 7 6 5 Metabolic limitation (Heat) Carmo-Silva et al. (212) Environ Exp Bot 83:1-11
Modeling A-Ci Response of Cotton Drought 21 - WW 12 A ( mol m-2 s-1) 1 1 8 8 6 6 4 4 2 2 - WL 12 1 8 8 6 6 4 4 2 2 2 Aj Ac Apred A - WL 12 1 - WW 12 4 6 8 1 12-1 Ci ( mol mol ) 2 4 6 8 1 12-1 Ci ( mol mol ) Well-watered vs. water-limited plants Carmo-Silva et al. (212) Environ Exp Bot 83:1-11
Modeling A-Ci Response of Cotton Drought 21 Cultivar Treatment Tleaf ( C) Vcmax Jmax (mmol m-2 s-1) Ci Ctrans A-limitation (mmol mol-1) WW 32.6 (.2) 171 (1) 249 (12) 281 (1) 281 (24) Ac + Aj WL 38.7 (.7) 31 (41) 356 (34) 196 (5) 412 (117) Ac WW 33.5 (.5) 215 (15) 315 (21) 244 (18) 315 (17) Ac WL 35.6 (.6) 259 (18) 361 (2) 24 (3) 367 (11) Ac Increased Tleaf, Vcmax and Jmax under WL conditions Ci < Ctrans under WL conditions (Rubisco limitation) Vcmax, maximum RuBP carboxylation rate; Jmax, maximum electron transport rate. Ctrans (Ci,Ac=Aj), CO2 concentration at which RuBP-consumption (Ac) and RuBP-regeneration (Aj) co-limit photosynthesis (A). When Ci < Ctrans, A is Ac-limited and, when Ci > Ctrans, A is Aj-limited. Carmo-Silva et al. (212) Environ Exp Bot 83:1-11
Take-Home Message Phenotyping photosynthetic traits in the field gives valuable information: Cotton genotypes with better photosynthetic performance under Drought & Heat Stress Wheat genotypes with better photosynthetic performance under optimal conditions
Acknowledgments USDA-ARS, ALARC, US Dr. Michael Salvucci Dr. Michael Gore Rothamsted Research, UK Prof. Martin Parry Dr. John Andralojc
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