Structure of Androecium, microsporogenesis and microgametogenesis

Structure of Microsporangium:

Development of microspores/pollen grain inside the anther is called Microsporogenesis.
Develeopment of a microsporangium
Development of microsporangium is eusporangiate type.
In transverse section young stamen is composed of homogenous mass of meristematic cells.
Very soon it becomes flattened and lobed.
Below the epidermis at four corners archesporial cells are differentiated.
These cells are longer in size, contains large nuclei and dense cytoplasm.
Archesporial cells divide by periclinal division to produce outer primary parietal layer and inner primary sporogenous layer.
Primary parietal layers divide periclinally and anticlinally to form 3 to 5 concentric layers of cells.
Outermost layer is endothecium. Wall of the endothecium is fibrous and helps in dehiscence of anther.
Below the endothecium are 1-3 layered middle layers.
Innermost layer is the tapetum. Tapetum is the nutritive layer of anther and get absorbed by the developing anther.
Meanwhile, sporogenous cells are differentiated into Microspore Mother Cells (MMC), which then divide meiotically to produce 4 haploid nuclei.
After wall formation, 4 microspores/pollen grains are produced in tetrad.
Arrangement of tetrad may be of tetrahedral, isobilateral, decussate, linear and T-shaped.

Development of male gametes/sperm cells inside the pollen grains is called as microgametogenesis.
The pollen grain is divided into two halves: a small generative nucleus and a larger vegetative nucleus.
The generative cell produces two male nuclei (gametes), whereas the vegetative cell produces the pollen tube.

This is the innermost layer of the anther wall.
It surrounds the sporogenous tissue.
All the food material passes to the sporogenous tissue through the tapetum.
Tapetum is of two types.
Amoeboid (plasmodial): inner and radial walls breakdown occur at early stage.
Secretory (glandular): Cells remain in position and secrete Ubisch bodies. Ubisch bodies are involved in external thickening of the exine.

It passes the nutrient from middle layers to the pollen sacs.
It contributes in pollen wall formation.
synthesises pollenkitt and tryphine, which bind pollen grain together and also help in effective pollination.
It synthesises callase enzyme for the separation of the microspore tetrads.

First published on 29-01-2026
Last updated on 29-01-2026