Floret of annual meadow grass, Poa annua

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Scanning electron micrograph of a floret of annual meadow grass, Poa annua. The picture shows two pairs of 1mm long anthers (brown), with a feathery female stigma (lilac) between. The stigma has captured windborne pollen grains (yellow) that adhere to its surface, and will germinate to produce a pollen tube. The tube, containing the male gametes, penetrates the stigmatic surface and grows down to the ovaries, where fertilisation takes place. Grasses are wind-pollinated; here, the anthers - containing pollen - have not yet opened. The pollen in the picture has come from a different floret, or a different plant. Grass pollen can be carried long distances when warm weather induces upward convection currents, causing allergic rhinitis (hay fever). P annua is widespread and common. Although annual, its long flowering season allows it to persist by self-seeding in lawns and as a garden weed.

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Size: 3468px × 5212px
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Photo credit: © DR JEREMY BURGESS/SCIENCE PHOTO LIBRARY / Alamy / Afripics
License: Licensed
Model Released: No

Keywords: allergic, annua, annual, anther, electron, fertilisation, fertilization, fever, floret, gamete, garden, grain, grass, hay, male, meadow, micrograph, poa, pollen, pollination, rhinitis, scanning, sem, stigma, tube, weed, wind