pollen

Pollen is fine powder produced by the male structures of seed plants. In flowering plants it is produced in the anthers of the stamen and contains the male gametophyte in a protective wall made of sporopollenin. The pollen grain typically consists of a tough outer layer called the exine and an inner layer called the intine; many species have apertures that regulate pollen germination. Pollen grains vary in size, shape, and surface ornamentation, features used to identify plants in palynology.

Pollen plays a central role in plant reproduction. When pollen lands on a compatible stigma, the pollen grain germinates and grows a pollen tube through the style toward the ovule. The generative cell divides to form sperm cells, which fertilize the egg and create a zygote, while the surrounding tissue develops into the seed and fruit. Pollination can occur by wind (anemophily), water, or animal vectors such as insects or birds; some species are highly specialized for a particular pollinator.

Pollen is also important in science and society. Palynology uses fossil and contemporary pollen to reconstruct past vegetation and climates, and to track environmental changes. Pollen grains are collected for forensic and archaeological purposes and for allergy forecasting. Pollen is a notable source of allergens; wind-pollinated grasses, trees such as birch, and ragweed are common causes of seasonal allergies.