Pollen is...

The Pollen Wall

Pollen Development

Pollen Cell Fate

Germ Cell Morphogenesis

Male Germ Unit

Progamic Phase

Pollen is the haploid microgametophyte generation in seed plants and is considered the male partner in sexual reproduction. In flowering plants pollen comprises either two or three cells when shed from the flower. Both pollen types possess a large vegetative cell containing within, a single generative cell (bicellular pollen) or sperm cell pair (tricellular pollen). Pollen shows a wide variation in size, shape and surface patterning. Pollen grains vary in diameter from 5 µm in Myosotis (forget-me-not) to more than 200 µm in Curcurbita (ie melon) and round, ellipsoid and multifaceted pollen types occur.

Pollen grains germinate on the surface of the stigma in the flower by forming a pollen tube which usually emerges through one of the apertures in the pollen grain wall. The vegetative cell which comprises the bulk of the pollen cytoplasm is responsible for the development of the pollen tube. The two sperm cells are then transported within the pollen tube and delivered to the embryo sac inside the ovule to allow fertilisation to occur.

Pollen diagram

Flowering plants undergo a unique sexual process called  'double fertilisation', in which one sperm cell fuses with the egg cell to form the diploid zygote (which forms the embryo), while the second sperm cell fuses with two haploid nuclei within the central cell to form the triploid primary endosperm. The primary endosperm nucleus then divides rapidly to support and nourish the developing embryo during seed development.

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