EFFECTS OF SOIL-PHOSPHORUS ON POLLEN PRODUCTION, POLLEN SIZE, POLLEN PHOSPHORUS-CONTENT, AND THE ABILITY TO SIRE SEEDS IN CUCURBITA-PEPO (CUCURBITACEAE)

To determine the effects of soil phosphorus on pollen production, poll en grain size, phosphate concentration per pollen grain, and the sirin g ability of pollen, two cultivars of the common zucchini (Cucurbita p epo) were grown under two soil phosphorus conditions in an experimenta l garden. Overall, soil phosphorus availability had a significant effe ct on reproductive output through the female function and on traits af fecting the male function of plants (staminate flower production, poll en production per flower, and pollen grain size). In addition, pollen produced by plants in the high phosphorus soils had a higher phosphate concentration than pollen produced by plants in the low phosphorus so ils. A pollen mixture experiment revealed that pollen produced by plan ts in the high phosphorus treatment sired significantly more seeds tha n pollen produced by plants in the low phosphorus treatment. This stud y showed that growing conditions such as soil phosphorus can influence the size of a pollen grain and its chemical composition, which, in tu rn, can affect its ability to sire mature seeds.