Name: Pollen-Pistil Interaction
Uploaded: 2019-07-19
Duration: 4 min 55 s
Description: Pollen Pistil interactions are the sequence of events that are decisive in the selection of apt pollen for maintaining genetic diversity. Comprehend this dyn...

Question

Describe in sequence the events that leads to the development of a 3 celled pollen grain from microspore mother cell in angiosperms.

Accepted Answer

The development of pollen grains takes place inside the microsporangia. The process of formation of microspore from microspore mother cells is called microsporogenesis.

The sporogenous tissue fills the whole interior of a microsporangium transformed into microspore mother cells or pollen mother cells. The mother cells round off and undergo meiosis to produce tetrads of microspores or pollen grains. Usually, the arrangement of microspores in tetrad is tetrahedral or isobilateral.

As the anther matures, the microspores dissociate from tetrads and develop into haploid pollen grains. Pollen grains are commonly globular in structure that is surrounded by highly resistant wall layers and cellular contents inside. Wall of pollen grain is called sporoderm. It has two layers, outer exine and inner intine. Inside the wall layer, the young pollen has a centrally placed nucleus embedded in dense cytoplasm covered by a plasma membrane. During the growth of pollen grains, vacuoles develop, it pushes the nucleus to one side near the wall. The protoplast then divides mitotically to form two unequal cells- a small generative cell and a large vegetative or tube cell. A layer of callose develops around the generative cell that separates the cell from the pollen grain wall. Later, the callose wall dissolves and the naked generative cell lies freely in the cytoplasm of the tube cell.

In some species, the generative cell divides into two nonmotile male gametes prior to the dehiscence of anther and the release of the pollen grains. Therefore, at the time of pollination, the pollen grain is either two-celled (generative cell + vegetative cell) or 3 celled (vegetative cell + two male gametes).

Describe in sequence the events that leads to the development of a 3 celled pollen grain from microspore mother cell in angiosperms.

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