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 the pollen load on the stigma of sweet pepper flowers (Capsicum annuum L.). Despite much variation, a linear increase in individual fruit weight 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 number. However, a relatively low seed number (50-100 seeds/fruit: 20-30 % 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 pollination treatments were applied to all the flowers of a plant, results could be quite different to those obtained when only a limited number of flowers were treated. Fruit set of the second fruit was reduced by the application of a high pollen load to the first flower, even when the first fruit aborted before it had accumulated much dry matter. Our results suggest that growth inhibition of the second fruit by seed number of the first fruit is controlled both by competition for limited assimilates, as well as by dominance due to the production of plant growth regulators by the developing fruit. (C) 1997 Annals of Botany Company.