The 2009 ASHS Annual Conference

In bell pepper (Capsicum annuum L.), developing fruits decrease size of subsequent fruits, possibly by reducing flower ovary size. The objective of this work was to determine the effect of developing fruits on ovary size of bell pepper flowers at anthesis. Plants were grown in growth chambers and pruned to two main axes. About 75 days after planting, one fruit per axis was allowed to set. Eight days after petal fall (DAPF), either 0 or 1 fruit per axis was allowed to develop, and examination of flowers began in both fruiting (FT) and non-fruiting (NFT) treatments. Flowers at anthesis were harvested continuously until fruits on the FT reached the mature green stage. Flower and ovary size (8-48 DAPF), cell size and number (8, 28, and 48 DAPF), and carbohydrate content of ovaries (33 DAPF) were measured. In general, fresh weight (FW) of whole flowers and ovaries in the NFT was greater compared to those in the FT.  In the FT, ovary FW of flowers that reached anthesis during the first 28 DAPF decreased gradually. However, ovary FW increased in flowers that reached anthesis after 28 DAPF, reaching a maximum FW at 48 DAPF, when the fruit demand for carbohydrates had presumably decreased. In the NFT, ovary FW of flowers at anthesis increased during the first 32 DAPF, then remained steady. The increase of ovary FW of flowers at anthesis in the NFT was accompanied by an increase in the cell size of the pericarp tissues but not in pericarp thickness.  Although developing fruits limited ovary size during the initial rapid growth of the fruits in the FT, the concentration of soluble sugars and starch in the ovaries was similar in both treatments. These findings indicate that rapid fruit growth reduces the ovary size of subsequently developed flowers by decreasing cell size, but not the number. The effect, however, does not appear to be mediated by carbohydrate differences.