EFFECTS OF SEED NUMBER ON COMPETITION AND DOMINANCE AMONG FRUITS IN CAPSICUM-ANNUUM-L

The effects of seed number on set, development and growth of a fruit, and on inhibition of later-developed fruits were studied by varying th e pollen load on the stigma of sweet pepper flowers (Capsicum annuum L .). Despite much variation, a linear increase in individual fruit weig ht with seed number could be observed. Seed number affected the growth rate rather than the growing period of fruit. When seed numbers were low, the probability of fruit setting was positively related to seed n umber. However, a relatively low seed number (50-100 seeds/fruit: 20-3 0 % of the maximum seed number) was sufficient for maximal fruit set. An increase in seed number increased the inhibitory effect of a fruit on set and growth of later-developing fruits. As a result, when pollin ation treatments were applied to all the flowers of a plant, results c ould be quite different to those obtained when only a limited number o f flowers were treated. Fruit set of the second fruit was reduced by t he application of a high pollen load to the first flower, even when th e first fruit aborted before it had accumulated much dry matter. Our r esults suggest that growth inhibition of the second fruit by seed numb er of the first fruit is controlled both by competition for limited as similates, as well as by dominance due to the production of plant grow th regulators by the developing fruit. (C) 1997 Annals of Botany Compa ny.