Rate of photosynthetic acclimation to fluctuating light varies widely among genotypes of wheat

Highlight Significant variation exists in the acclimation time of photosynthesis following dark-to-light transitions across wheat genotypes, under field and controlled conditions. Slow acclimation reduced daily carbon assimilation by up to 16%. Crop photosynthesis and yield are limited by slow photosynthetic induction in sunflecks. We quantified variation in induction kinetics across diverse genotypes of wheat for the first time. In a preliminary study using penultimate leaves of 58 genotypes grown in the field, we measured induction kinetics for maximum assimilation rate ( A max ) after a shift from full darkness to saturating light (1700 μmol m −2 s −1 ) with 1-4 replicates per genotype. We then grew 10 of these genotypes with contrasting responses in a controlled environment and quantified induction kinetics of carboxylation capacity ( V cmax ) from dynamic A vs c i curves after a shift from low to high light (50 to 1500 μmol m −2 s −1 ), with 5 replicates per genotype. Within-genotype median time for 95% induction ( t 95 ) varied from 8.4 to 23.7 min across genotypes for A max in field-grown penultimate leaves, and from 6.7 to 10.4 min for V cmax in chamber-grown flag leaves. Our simulations suggested that non-instantaneous acclimation reduces daily net carbon gain by up to 16%, and that breeding to speed up V cmax induction in the slowest genotype to match that in the fastest genotype could increase daily net carbon gain by more than 4%, particularly for leaves that experience predominantly short-duration sunflecks.