page_title: Cucurbita
section_title: Reproductive biology
hierarchical_section_title: Cucurbita / Reproductive biology
caption_attribution_description: English: Peponapis pruinosa
context_page_description: Cucurbita is a genus of herbaceous vines in the gourd family, Cucurbitaceae native to the Andes and Mesoamerica. Five species are grown worldwide for their edible fruit, variously known as squash, pumpkin, or gourd, depending on species, variety, and local parlance, and for their seeds. Other kinds of gourd, also called bottle-gourds, are native to Africa and belong to the genus Lagenaria, which is in the same family and subfamily as Cucurbita, but in a different tribe. These other gourds are used as utensils or vessels, and their young fruits are eaten much like those of Cucurbita species.
  Most Cucurbita species are herbaceous vines that grow several meters in length and have tendrils, but non-vining "bush" cultivars of C. pepo and C. maxima have also been developed. The yellow or orange flowers on a Cucurbita plant are of two types: female and male. The female flowers produce the fruit and the male flowers produce pollen. Many North and Central American species are visited by specialist bee pollinators, but other insects with more general feeding habits, such as honey bees, also visit.
context_section_description: All species of Cucurbita have 20 pairs of chromosomes. Many North and Central American species are visited by specialist pollinators in the apid tribe Eucerini, especially the genera Peponapis and Xenoglossa, and these squash bees can be crucial to the flowers producing fruit after pollination.
  When there is more pollen applied to the stigma, more seeds are produced in the fruits and the fruits are larger with greater likelihood of maturation, an effect called xenia. Competitively grown specimens are therefore often hand-pollinated to maximize the number of seeds in the fruit, which increases the fruit size; this pollination requires skilled technique. Seedlessness is known to occur in certain cultivars of C. pepo.
  The most critical factors in flowering and fruit set are physiological, having to do with the age of the plant and whether it already has developing fruit. The plant hormones ethylene and auxin are key in fruit set and development. Ethylene promotes the production of female flowers. When a plant already has a fruit developing, subsequent female flowers on the plant are less likely to mature, a phenomenon called "first-fruit dominance", and male flowers are more frequent, an effect that appears due to reduced natural ethylene production within the plant stem. Ethephon, a plant growth regulator product that is converted to ethylene after metabolism by the plant, can be used to increase fruit and seed production.
  The plant hormone gibberellin, produced in the stamens, is essential for the development of all parts of the male flowers. The development of female flowers is not yet understood. Gibberellin is also involved in other developmental processes of plants such as seed and stem growth.
caption: Cucurbita female flower with pollinating squash bees
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