Dynamic acclimation of source capacity in fluctuating light and temperature environments

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Wheat is one of the most important staple food crops and high grain yields are essential for global food security. Breeding raised yields continuously over the past century, however yield potential is increasingly suppressed by challenges associated with climate change and regulatory restrictions on crop inputs. Our extensive previous work confirmed that limitations to wheat yield potential are primarily determined by traits implicated in source-sink relations. The aim of this subproject in the Package Proposal “Wheat source-sink relationships and limitations (WheatSouSi)” is to understand the effects of environmental fluctuations on the formation, acclimation and limitation of canopy source capacity.Plants constantly acclimatize their photosynthetic capacity to fluctuating light and temperature environments. Acclimations are dynamic physiological processes affecting the size and the capacity of photosynthetic organs, which determine source capacity of winter wheat for grain filling. Although light and temperature acclimation of photosynthesis have been well studied using constant light and temperature environments, our knowledge about the acclimation to fluctuating light and temperature conditions is rare. Based on the hypothesis that synthesis rates of photosynthetic proteins depend non-linearly on light and temperature, we first propose a mechanistic model of photosynthetic protein turnover to describe the acclimation to fluctuating light and temperature. Second, a series of growth chamber experiments are planned to parameterize and to validate the proposed model in 50 winter wheat cultivars. The differences in photosynthetic acclimation strategies between cultivars can be characterized by their parameters in the model. Additionally, the combined effects of light and temperature on the coordination between stomatal morphology, photosynthetic induction and water use efficiency at leaf level will be quantified and integrated into static and dynamic functional-structural plant models (FSPMs) to understand how canopy source capacity can be maximized by photosynthetic acclimation strategies. To synthesize the outcomes of all results, structural equation modelling will be used to systematically test the strength and significance of causal interdependencies between physiological traits, source strength, sink strength and grain yield. The knowledge gain will facilitate a better understanding of crop physiology and improve crop models describing source and sink dynamics.