Pollination, Pollen Viability and Pistil Receptivity in Cucurbita pepo

Cucurbita pepo carries male and female flowers on the same plant,and is pollinated by nectar-collecting bees. The nectaries aredimorphic in the two sexes and pollen is loaded and unloadedas the bees gain access to the nectar. Both types of flowerare open for only 6 h (from 0600 h to 1200 h); male flowersopen and close half an hour earlier than female flowers. Thelatter produce more nectar and are visited more often by thebees than the male flowers. Pollen viability determined by fluoresceindiacetate (fluorochromatic reaction) decreases by 20% duringanthesis and more rapidly after the flower closes. This decreaseis due to dehydration of the grain, especially around the porewhere the intine is exposed. An unusual feature of this speciesis that the grains do not dehydrate before anther dehiscence.Female receptivity has two aspects, that of the stigma lasting4 d, and that of the ovules lasting 2 d. The receptivity ofthe two sexes and the short period of anthesis are discussedin the light of the reproductive ecology of the species.Copyright1993, 1999 Academic Press Entomophilous pollination, anthesis, nectars, pollen viability, female receptivity, bees, pollinator efficiency, courgette Cucurbita pepo, Cucurbitaceae