Effect of Temperature on Key Physiological Responses of Grapevine Leaf

The effects of temperature on the physiological responses of self-rooted cv. Trebbiano grapevines in three growth chambers were studied at 20°C, 27.5°C, and 35°C and compared to those of control plants grown in open air. The parameters recorded were photosynthesis, transpiration, stomatal conductance monitored with an LCA 2 (ADC) infrared-gas analyzer, vine development, and leaf growth and chlorophyll content. The lowest net photosynthesis values were recorded in vines grown at 35°C and were closely correlated to chlorophyll content, the latter expressed per unit of leaf area; the effect of temperature on stomatal conductance was less marked. The accumulation of dry matter was correlated to average photosynthesis. The findings suggest that photosynthesis in plants grown at 35°C depends not on stomatal opening but on biochemical factors of an enzymatic nature.