Pollination of Cotton

Gossypium hirsutum is generally self-pollinating, but in the presence of suitable insect pollinators can exhibit cross-pollination. Bumble bees (Bombus spp.), Melissodes bees, and honey bees (Apis mellifera) are the primary pollinators. Concentration of suitable pollinators varies from location to location and by season and is considerably suppressed by insecticide use. If suitable bee pollinators are present, distribution of pollen decreases considerably with increasing distance. In an experiment in which a cotton field was surrounded by a large number of honey bee colonies and movement of pollen was traced by means of fluorescent parti cles, 1.6 % of the flowers on plants 150 to 200 feet away showed the presence of the particles.

Gossypium tomentosum seems to be pollinated by lepidopterans, presumably moths. The stigma in G. tomentosum is elongated, and the plant seems incapable of self-pollination until acted upon by an insect pollinator. The flowers are unusual too, because they stay open at night. Most Gossypium flowers are ephemeral: They open in the morning and wither at the end of the same day.

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