Effect of Heat Stress on Assimilate Metabolism in Tomato Flower Buds

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Abstract
Assimilate import by flower buds in two cultivars of tomato (Lycopersicon esculentum Mill.) was inhibited by heat stress. With increasing temperature, levels of sucrose in the source organ increased while levels of starch decreased. The transport of radioactive carbon was correlated with the starch content of the flower buds. In Saladette, a heat-tolerant cultivar, conversion of the imported carbon to starch occurred to a greater extent than in Roma VF, a heat-sensitive cultivar. Uptake of sucrose from agar medium by detached flower buds was negatively correlated with their internal ratio of sucrose to hexoses. Glucose uptake from agar medium by detached flower buds decreased with increasing temperatures. Sucrose hydrolysis was negatively affected by high temperatures, and this was more pronounced in the heat-sensitive than in the heat-tolerant cultivar. The effect of heat stress on assimilate translocation from the leaves to the sink organ is discussed.