Structure and Development of Anther

In flowering plants, the male reproductive organ is the androecium — a whorl of stamens present in the flower. Hormonal and structural changes in the plant trigger the formation of the floral primordium, from which both the androecium and gynoecium differentiate.

A typical stamen consists of two main parts:

Lobes and Theca:

A typical anther is bilobed with each lobe containing two theca, making the anther dithecous. A longitudinal groove — the line of dehiscence — runs between the two theca of each lobe. In transverse section (T.S.), the anther appears as a tetragonal (4-sided) structure with 4 microsporangia at the corners.

Anther at a Glance:

The 4 Wall Layers of Microsporangium (T.S. of Anther):

Each microsporangium is enclosed by 4 concentric wall layers arranged from outside to inside:

T.S. of a mature anther

A-E. Development of microsporangium: A·D. successive stages of the development of microsporangium (pollen sac); E. a mature pollen sac in a transverse section. 

Centre of Microsporangium — Sporogenous Tissue:

• A compact mass of homogeneous cells called sporogenous tissue
• All cells are diploid (2n)
• These cells either directly or after mitotic divisions become Pollen Mother Cells (PMC) / Microspore Mother Cells (MMC)
• Each MMC undergoes meiosis → produces 4 haploid microspores arranged as a tetrad

Dehiscence is the mechanism by which a mature anther splits open at the stomium (line of dehiscence) to release its pollen grains for pollination.

Mechanism - Step by Step:

1. The mature anther dries up — loses water by desiccation.
2. The sterile strip between the two pollen sacs of each lobe disintegrates → two sacs merge into a single cavity.
3. Endothecium cells contract as their thick inner walls pull inward, bringing radial walls closer.
4. This mechanical tension ruptures the anther wall at the thin-walled stomium.
5. Pollen grains are released and dispersed by pollination agents (wind, insects, water, animals, etc.).

• A typical anther is dithecous and tetrasporangiate, having two lobes, each with two microsporangia (pollen sacs).
• Microsporangia contain sporogenous tissue, which develops into microspore mother cells that form pollen grains.
• The anther wall has four layers: epidermis, endothecium, middle layers, and tapetum.
• The tapetum provides nutrition to developing pollen, and microspore mother cells undergo meiosis to form haploid microspores.
• During anther dehiscence, the endothecium helps in rupture at the stomium, releasing pollen grains for pollination.