Thermal acclimation of photosynthesis to experimental warming is season-dependent for winter wheat (Triticum aestivum L.)

Temperate plants may show different photosynthetic acclimation capacities, involving varying physiological processes/mechanisms, during different seasons in response to global warming because of seasonal climate variation. Thus, we conducted field warming experiments for winter wheat in its four seasonal periods. These experiments allowed us to examine the thermal acclimation of photosynthesis and the underlying processes/mechanisms (RuBP-carboxylation, RuBP-regeneration, stomatal conductance and the balance between respiration and photosynthesis) to both seasonality and warming effects as well as the interaction between them. We found winter wheat displayed nonlinear acclimation to the seasonal temperature change, and significant acclimation to experimental warming in the four seasons. However, the acclimation capability in response to experimental warming was lower in January than November/April/May. Importantly, the underlying physiological processes/mechanisms to warming effects vary among seasonal periods: RuBP carboxylation contributed to the acclimation of photosynthesis in November and April, while the balance between respiration and photosynthesis caused the major change in January, and lower stomatal conductance played the most important role in May. These results could give insights into the decrease in productivity and increase of biomass accumulation and could help to predict acclimation capability and underlying processes to global warming. In addition, photosynthetic parameters reported here could be used to incorporate seasonal dynamics of thermal acclimation into physiological-process-based ecosystem models.