T.S of Bilobed Anther

A transverse cross-section reveals the internal layers of the bilobed anther. A well-differentiated anther wall has four layers-

1. Epidermis: It is the outermost layer of the anther and has a protective function. It prevents water loss and provides structural support. The epidermis also helps in anther dehiscence. The point of dehiscence, known as the stomium, can be longitudinal, transverse, apical, or valvular. In the stomium region, epidermal cells differentiate into specialized cells that split open at anther maturity, allowing the anther to burst open and release pollen grains.
2. Endothecium: The endothecium is a layer beneath the epidermis, called the hypodermal layer. It is typically single-layered and found in the protruding part of the anther in most angiosperms. As the anther matures, the endothecium cells elongate radially to aid in dehiscence. It also provides structural support to the anther.
3. Middle layers or intermediate layer: The intermediate layer generally consists of 1 to 3 layers. The thin-walled cells of the intermediate layer contain food material such as starch, which nourishes the microspores. During pollen development, the reserved food gets mobilized. Middle layers are usually short-lived and are crushed during meiosis in the microspore mother cells.
4. Tapetum: The tapetum is the innermost single layer of the anther wall and surrounds the sporogenous tissue. It secretes necessary hormones and enzymes for pollen development and pollen germination. In many angiosperms, the tapetum has a dual origin: the outer part is derived from the parietal layer, and the inner part is formed by the connective tissue. During micro-gametogenesis, the tapetum begins to degenerate and is fully degraded by the time of dehiscence.

The bilobed anther is a part of the stamen and serves as the site of pollen production and dispersal. Typically, an anther is bilobed, dithecous, and tetrasporangiate in most angiosperms with a few exceptions. The structure of a bilobed anther consists of two lobes, each containing a pair of microsporangia or pollen sacs called thecae. These thecae are where pollen grains develop and mature.

The two sporangia in each lobe become confluent at maturity and cause lysis of the septum separating them. At maturity, the anther dehisces along a slit termed the stomium to release the pollen. Mature pollen carries sperm cells to the stigma of the female reproductive part for fertilization. In this article, we will read about the bilobed anther diagram and the structure, and function of the bilobed anther.