Floral abscission and changes in sucrose phosphate synthase and invertase activities in water deficient tomato

A study was conducted to determine the photosynthesis, sucrose phosphate synthase and invertase activities in four tomato (Lycopersicon esculentum Mill) cultivars, e.g. Mruthyunjaya, Pusa early dwarf (PED), Arka Ahuthi and Pusa Ruby exhibiting differential response in floral abscission under water stress. Among the four cultivars, Arka Ahuthi and Pusa Ruby were found to be more susceptible to abscission under water stress as indicated by more than 55.0% abscission of flower buds and flowers in these cultivars. Water stress caused a substantial decrease in photosynthesis in all the cultivars, although the degree of decrease varied with cultivars. In the cultivars where the abscission of flowers and flower buds was more (Arka Ahuthi and Pusa Ruby), the reduction in photosynthesis was more (53–61.5%) compared to the cultivars where the abscission was relatively less (Mruthyunjaya and PED) (39.0–53.0%) during stress. There was a considerable decrease in SPS activity during stress in susceptible cultivars. In susceptible cultivars, the invertase activity in reproductive organs as well as leaf and developing young fruits decreased under stress. The decrease in photosynthesis along with a reduction in invertase activity may be important contributing factors for the abscission of flower and flower buds in abscission susceptible tomato cultivars under water stress.