Microsporangia

Microsporangium is a structure in the plant’s male reproductive organ where the development of pollen takes place.

Structure of Microsporangia

A microsporangium appears to have a circular outline when viewed transversely. It is surrounded by four layers:

  • Epidermis
  • Endothecium
  • Middle layers
  • Tapetum

The outer three layers protect the pollen and help in the splitting of anther to release the pollen. The tapetum nourishes the pollen grain. The cells of the tapetum are multinucleated and have dense cytoplasm. A young anther comprises of a group of compactly arranged homogenous cells called sporogenous tissue.

Also read: Pollen and Embryo-Sac

Sporogenous Tissue

These are located at the centre of each microsporangium in a young anther. With the development of the anther, the sporogenous cells undergo meiotic division to form microspore tetrads. Each sporogenous cell is known as pollen mother cell or microspore mother cell. This process by which a microspore is formed from the pollen mother cell is known as microsporogenesis. The microspores are arranged in the form of a tetrad. As the anther matures it dehydrates and the microspores dissociate from each other and develop into a pollen grain.

Pollen Grain

The matured pollen grain contains two cells: a generative cell and a pollen tube cell. The generative cell is present within the larger pollen tube cell. The tube cells form the pollen tube on germination. The generative cell migrates into the ovary through the pollen tube. Inside the pollen tube, the generative cell divides into two gametes or sperms. The anther matures and releases the pollen grains.

Also read: Pre-fertilization

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