Effect of Heat Stress on Assimilate Partitioning in Tomato

Differences in assimilate partitioning in response to heat stress were observed between the heat-sensitive tomato cultivar, Roma VF and the heat-tolerant cultivar, Saladette. Transport of carbon to the trusses and apex was inhibited in both cultivars, particularly in Roma VF. Basipetal transport to the roots was inhibited in Roma VF only. Assimilate partitioning within the young truss was also affected by heat stress in both cultivars, but was more pronounced in Roma VF : at higher temperatures more 14C was found in the peduncle and in the older flower buds than in the younger flower buds. The youngest flower buds were more sensitive than other parts of the truss to heat stress. The uptake of [14C]sucrose by detached flower buds from agar medium was lower at higher temperatures. Alteration of assimilate partitioning was also observed following the application of GA3 + Kinetin to the first truss. The possible relationship between flower-set in tomato and carbohydrate stress is discussed.