Dry Matter Assimilation and Partitioning in Pepper Cultivars Differing in Susceptibility to Stress-induced Bud and Flower Abscission

Stress-induced abscission of buds and flowers is a constraint to the production of peppers ( Capsicum annuum L.). Susceptibility of pepper cultivars to stress-induced abscission may be related to assimilate levels and partitioning. Growth analysis experiments were conducted in the field to determine whether cultivars differing in susceptibility to stress-induced abscission showed corresponding differences in growth rates and dry matter partitioning when subjected to low light stress. With the stress susceptible cultivar 'Shamrock', reduction in net assimilation rate (NAR) and relative growth rate (RGR) was greater under low light stress than with the more tolerant cultivar 'Ace'. Compared to 'Ace', 'Shamrock' partitioned a smaller proportion of dry matter into reproductive organs and a larger proportion into expanded leaves. Cultivars did not differ in the amount of dry matter partitioned to young leaves or in the extent to which accumulation of dry matter by young leaves was reduced by low light stress. Other experiments conducted in growth chambers and greenhouse examined the effect of removal of leaves less than 3 cm long on high temperature and low light stress-induced bud and flower abscission. For both 'Ace' and 'Shamrock', abscission was not altered by removal of these leaves. Preferential partitioning of assimilate to young leaves does not appear to be involved in stress-induced abscission in these pepper cultivars.