ANOTHER WALL โ STRUCTURE AND FUNCTIONS
Introduction
The anther is the terminal part of the stamen that produces and stores pollen grains. It is usually
bilobed, and each lobe contains two pollen sacs or microsporangia, making the anther
tetrasporangiate. The wall of the anther surrounds these pollen sacs and plays a vital role in the
protection, nourishment, and release of pollen grains.
Structure of Anther Wall
The mature anther wall is made up of four concentric layers arranged from outside to inside โ
epidermis, endothecium, middle layers, and tapetum.
1. Epidermis:
The epidermis forms the outermost single layer of cells of the anther wall. It acts as a protective
covering, safeguarding the developing microsporangia from mechanical injury and desiccation. The
cells are compactly arranged and sometimes covered with a cuticle. During dehiscence, the
epidermis may get stretched or ruptured due to internal pressure.
2. Endothecium:
The endothecium lies just below the epidermis and is composed of a single layer of cells with
fibrous thickenings on the inner tangential and radial walls. These fibrous thickenings, made of
cellulose and lignin, help in the dehiscence of the anther. As the anther matures and loses
moisture, the thickened endothecial cells contract unevenly, causing tension that splits the anther
along a region called the stomium, releasing the pollen grains.
3. Middle Layers:
The middle layers are one to three layers of thin-walled parenchymatous cells situated between the
endothecium and tapetum. These layers are temporary in nature. In the young anther, they provide
mechanical support and nourishment to the developing sporogenous tissue. As the anther matures,
the middle layers degenerate, allowing more space for the developing pollen sacs.
4. Tapetum:
The tapetum is the innermost layer of the anther wall, surrounding the sporogenous tissue. It
consists of large, dense, and metabolically active cells, often multinucleate or polyploid. The
tapetum serves as the nutritive layer, supplying essential nutrients, enzymes, and materials for
pollen wall formation (especially the exine). It also secretes enzymes like callase, which helps in
breaking down the callose wall around the microspores. The tapetal cells eventually degenerate
after fulfilling their function.
Functions of the Anther Wall
1. Protection: The epidermis and endothecium protect the developing pollen sacs from
desiccation, mechanical injury, and pathogens.
2. Nutrition: The tapetum supplies nutrients, enzymes, and precursors for pollen wall development
and pollen maturation.
3. Support: The middle layers provide temporary mechanical support and contribute to the
nourishment of sporogenous tissue during early stages.
4. Dehiscence: The fibrous thickening in the endothecium helps in the proper dehiscence of the
anther, ensuring timely release of mature pollen grains.
Conclusion
The anther wall, composed of four distinct layers โ epidermis, endothecium, middle layers, and
tapetum โ plays an essential role in protecting, nourishing, and aiding in the release of pollen
grains. Each layer performs a specific function that together ensures successful pollen development
and dispersal, which are crucial for the process of fertilization in flowering plants.
