Effect of pistil age on pollen tube growth, fruit development and seed setin Cucurbita pepo L.

The effects of pistil age on pollen tube growth, fruit development and seed set were studied in Cucurbita pepo L., the flower of which opens for only six hours. Stigma receptivity lasts four days, from one day before until tw o days after anthesis. Style receptivity lasts three days, from the day bef ore to the day after anthesis. Ovule receptivity lasts two days: the day of anthesis and the day before. The rate of pollen tube growth varies in diff erent parts of the pistil and in relation to pistil age. In the stigmatic a nd stylar region, the tubes grow faster if pollination occurs the day befor e anthesis; in the ovary they grow faster when pollination occurs at anthes is. In the receptacle region, where the transmitting tissue is reduced, the growth rate decreases independently of the time of pollination. The fruits are larger and heavier with more seeds when pollination occurs at anthesis . There is a positive correlation between seed number and fruit weight when pollination occurred at anthesis and the day before.