The effect of heat stress on processes related to carbohydrate partitioning was investigated in young bell pepper (Capsicum annum L. cv. Maor) plants in relation to abscission of their reproductive organs at different stages of development.None of the reproductive organs abscised after 5 d in a normal day/night temperature regime (25/18°C). With a temperature regime of 35°C day, 25°C night, abscission occurred in only a small portion of the flower buds and none of the flowers and fruitlets. However, when temperatures in the day and night were reversed (25/35°C, day/night) all the buds and some of the flowers abscised during that time period. The young fruit at the first node did not abscise under any temperature regime. The abscission rate of the flower buds was reduced under heat stress if the developing fruit at the first node had been removed.High temperature during either the light or dark periods reduced the export of [14C]sucrose from the source leaf (fed for 48 h with [14C]sucrose).Both heat stress and fruit presence reduced the relative amount of [14C]sucrose which was exported to the flower buds, flowers and roots. Likewise, these treatments reduced the concentration of reducing sugars in the reproductive organs. Concomitantly, the heat stress and fruit presence on the first node reduced the activity of soluble acid invertase in the flower buds and the roots, but not in young leaves.Overall, the results show that heat stress causes alternation in sucrose distribution in the plant, but may also have specific effects on metabolic activities related to sucrose import and utilization in flower buds and flowers which in turn may enhance their abscission.Bell pepper, (Capsicum annuum L. cv. Maor), abscission, acid invertase, heat stress, reproductive organs, sink leaves. © 1991 Annals of Botany Company.
