Stomatal and non-stomatal limitations at different leaf temperatures to the photosynthetic process during the post-harvest period for Vitis vinifera cv. Chardonnay vines.

Photosynthesis in Vitis vinifera cv. Chardonnay leaves was measured during the post-harvest period in relation to leaf temperatures and chloroplast CO2 concentrations to evaluate the limitations to photosynthesis once the fruit sink was removed. Photosynthesis was optimal at 30 degrees C and rates were higher at high compared to low temperatures, consistent with the current climate. Stomatal limitation of photosynthesis ranged from 20% at low temperatures to 45% at high temperatures. RuBP carboxylation (V-cmax) and regeneration (J(max)) were optimal at 39 and 36 degrees C, but their capacities were low below 25 degrees C accounting for low assimilation rates. Chloroplast CO2 concentration transitioning between RuBP regeneration and RuBP carboxylation-limited assimilation, increased steeply with increasing temperature. Assimilation of Chardonnay leaves was limited by RuBP regeneration below 35 degrees C and by RuBP carboxylation above 35 degrees C, consistent with increased photorespiration at high temperatures. Results provide a quantitative explanation for the photosynthetic performance of Chardonnay vines in the post-harvest period.