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

Abstract

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.