Pollen of timothy grass, Phleum pratense
Numéro d’image : 13444786
| Scanning electron micrograph of pollen grains of timothy grass, Phleum pratense. The picture shows six grains, one of which has its germination pore visible (blue). The pore is the site within the wall through which the pollen tube emerges when the grain encounters a female stigmatic surface. The tube conveys the male gametes to the ovaries. Grasses are wind-pollinated plants, although hoverflies may sometimes effect pollination. The grains are light and very small - about 30 microns across. They are shed in large numbers and usually travel only a few metres from the plant. Many will fail to reach their intended destination - a female floret; but once airborne, they may cause allergic rhinitis - hay fever"" - in susceptible humans. Rarely, convection currents can carry pollen to a height of 1km above ground. P. pratense is the most common cause of hay fever in the grass pollen season." | |
| Licence : | Droits gérés |
| Crédit: | Science Photo Library / Burgess, Dr. Jeremy |
| Taille de l’image : | 3468 px × 5212 px |
| Model Release : | Non requis |
| Restrictions : | - |
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