NAME: Helianthus annuus C. Linnaeus

PLANT FAMILY: Asteraceae

COMMON NAME: common sunflower

APERTURATION: Tricolporate

ORNAMENTATION: Echinate

POLLINATION SYNDROME: Entomophilous

SIZE: 40µm in polar view, 38 µm in equatorial

SHAPE: Spheroidal

FLOWERING DATE: July - March in Texas

NOTES: This scanning electron micrograph is a cluster of pollen grains stuck together. Normally each pollen grain is separate. Pollen from almost all members of this plant family, Asteraceae, have processes. Processes vary greatly in size, shape, and number. Pollen grains from plants in the Asteraceae are usually divided into categories. The number of categories depends on the palynologist identifying the pollen grains. The flowering head of Helianthus annuus is actually two types of flowers: the yellow outer petals (ray florets) and dark brown inner petals (disk florets). The flowers are visited by many insects. Pollen from Helianthus annuus pollen has been found in honey samples and on corn earworm adults.