Nectar Secretion, Reabsorption, and Sugar Composition in Male and Female Flowers of Cucurbita pepo

Nectar volume and sugar composition of male and female flowers of Cucurbita pepo L. (squash), a vine native to tropical Mexico, were studied in an Italian botanical garden. Flowers opened at dawn and closed at noon. Both sexes were extremely rewarding compared with most bee-pollinated flowers, producing 22-40 mg sugar/flower in 6 h. Female flowers produced significantly more nectar sugar than did males, mainly because of a higher concentration of sugars in nectar (440 vs. 325 mg/mL). The temporal pattern of secretion was similar in the two sexes, and both nectars were sucrose rich. Sugar composition did not vary during anthesis. By 6 h after flower closure, nectar volume and sugar concentration had decreased drastically, especially in female flowers. Cucurbita pepo has the ability to reabsorb most or all unconsumed nectar.