Tuesday, September 18, 2007

The structure of pollen

Each pollen grain contain vegetative cells only one in the greater part flowering plant but several in other seed plants and a generative cell contain a tube nucleus that produces the pollen tube and a generative nucleus that divide to form the two sperm cells. The group of cells is surrounded by a cellulose cell wall and a thick, rough outer wall made of sporopollenin.

Pollen is created in the microsporangium contained in the anther of an angiosperm flower, male cone of a coniferous plant, or male cone of other seed plants. Pollen grains come in a broad multiplicity of shapes, sizes, and surface markings characteristic of the species see photomicrograph at right. Most, but surely not all, are spherical, Pollen grains of pines, firs, and spruces are wing. The minimum pollen grain that of the Forget-me-not plant (Myosotis sp.), is approximately 6 ┬Ám (0.006 mm) in diameter.

Pollen grains may have furrows, the course of which classify the pollen as colpate or sulcate. The number of furrows or pores helps categorize the flowering plants, with eudicots having three colpi (tricolpate), and other groups having one sulcus.

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