Effect of Heat Stress on Assimilate Partitioning in Tomato

Differences in assimilate partitioning in response to heat stresswere observed between the heat-sensitive tomato cultivar, RomaVF and the heat-tolerant cultivar, Saladette. Transport of carbonto the trusses and apex was inhibited in both cultivars, particularlyin Roma VF. Basipetal transport to the roots was inhibited inRoma VF only. Assimilate partitioning within the young trusswas also affected by heat stress in both cultivars, but wasmore pronounced in Roma VF: at higher temperatures more ¹⁴Cwas found in the peduncle and in the older flower buds thanin the younger flower buds. The youngest flower buds were moresensitive than other parts of the truss to heat stress. Theuptake of [¹⁴C]sucrose by detached flower buds from agar mediumwas lower at higher temperatures. Alteration of assimilate partitioningwas also observed following the application of GA₃+Kinetin tothe first truss. The possible relationship between flower-setin tomato and carbohydrate stress is discussed. Lyeopersicon esculentum Mill., carbon translocation, starch