THE SUSCEPTIBILITY OF PEPPER (CAPSICUM-ANNUUM) TO HEAT-INDUCED FLOWERABSCISSION - POSSIBLE INVOLVEMENT OF ETHYLENE

Heat stress causes abscission of flowers in pepper plants and thus red uces yield. In the present study, we investigated the involvement of e thylene in heat-stress related flower abscission, by comparing the res ponse of flowers of bell pepper, cv. Maor, known to be sensitive to fl ower abscission, and flowers of paprika, cv. Lehava, a resistant culti var of Capsicum annuum. Their differing susceptibilities to high tempe ratures depend on light. Under high-temperature, high-light conditions , bell pepper was less susceptible than paprika, but, under high-tempe rature low-light, bell pepper was more susceptible. At high temperatur es, flower explant abscission was much higher with bell pepper than pa prika. Ethylene production (EP) by bell pepper explants reached a maxi mum at 34-degrees-C and decreased at higher temperatures (42 and 48-de grees-C), while in paprika EP rates were lower and reached the maximum at 42-degrees-C. Explants of bell pepper flowers were more susceptibl e to exogenous ethephon than paprika flowers. The sensitivity of a col lection of pepper cultivars to heat induced flower abscission was more closely correlated with their flower sensitivity to ethephon than wit h the flower EP rate. We suggest that the differential susceptibility of bell pepper and paprika to heat stress is a result of both differen t ethylene production by their flowers and their differing sensitiviti es to ethylene produced under high-temperature stress. However, the se nsitivity of the flower to ethylene may be more important in inducing their abscission.