What is Anther? Structure and Development of Anther:
The male reproductive whorl of the flower is called androecium. An individual member of the androecium is called the stamen. The stamen consists of filament, connective, and anther.
Definition of Anther:
- The anther is the part of the stamen in a flower where pollen is produced.
- The anther is the part of a stamen that produces and contains pollen grains.
What is Anther:
The anther is the terminal portion of the flower stamen. They are sacks lined internally by sporogenic tissue, where pollen grains are produced. Anthers can be formed by one or two theca, or compartments, divided internally into two locules or stores, where pollen is stored.
Development of Anther:
- Stamens produce from the stamen primordia in the flower bud, and the top of the stamen primordia is the area where anthers develop.
- In the early stage of anther development, the structure is simple, the outer layer is a layer of the original epidermis, and an inner side is a group of basic meristems.
- Soon, the anthers are quadrangular because of the rapid division at the four corners of the anthers.
- An immature stage of the anther is represented by a group of parenchymatous tissue surrounded by a single-layered epidermis.
- The anther is generally dithecous (having two lobes) and tetrasporongiate.
- Each monothecous anther contains two pollen sacs. In dithecous anther four pollen sacs are present. Therefore, it is tetrasporongiate.
- The heterogeneity (differentiation) arises when some hypodermal cells get transformed into archesporial cells.
- The archesporial cell divides into an inner sporogenous cell and an outer primary parietal cell.
- Sporogenous cell forms sporogenous tissue. Each cell of sporogenous tissue is capable of giving rise to a microspore tetrad.
- The parietal cell undergoes divisions to form anther wall layer.
- The wall of mature anther consists of four layers.
- The epidermis is the outermost protective layer made up of tabular (flattened) cells.
- Endothecium is a sub-epidermal layer made up of radially elongated cells with fibrous thickenings.
- Inner to endothecium is the middle layer made up of thin-walled cells (1-2 layered), which may disintegrate in mature anther.
- Tapetum is the innermost nutritive layer of anther wall. It immediately encloses the sporogenous tissue (microspore mother cells).
- After the pollen grains mature, the fiber layer cells lose water, and the resulting mechanical force causes the anthers to break at the crack, and the pollen grains are scattered from the cracks formed by the longitudinal axis of the crack.
- The pollen sac wall disappeared due to the disintegration of the tapetum, or only traces remained, leaving only the epidermis and the fibrous layer.
Structure of Anther:
- The anther is the sac-like part of the filament that is swollen at the top and is the main part of the stamens that produces pollen.
- The anthers of most angiosperms are composed of 4 pollen sacs (2 in a few plants), which are divided into left and right halves, which are connected by a medicinal septum in the middle.
- In mature anthers, the separation between two anther sacs on the same side is broken to form a single chamber, giving the anther of 4 anthers the appearance of two anther sacs.
- The anther is composed of four layers- epidermis, endothecium, middle layer, and tapetum layer.
- The tapetum is a special cell layer around the pollen sac with a dual or multi-nucleated structure.
- The cells contain more RNA and protein, as well as nutrients such as oil and carotenoids, which can supply the nutrients required for the development of pollen grains.
- When the pollen matures, the pollen sacs open and release the pollen.
Layers of Anther:
- The outer wall has a cuticle, which contains sporopollenin, and some plants also have stomata and trichomes on the epidermis.
- During the young period of anthers, the inner wall cells of the anther contain a large number of starch granules .
- When the anther is close to maturity, the cells increase radially, and the storage material gradually disappears.
- The walls of the cell wall except the tangential wall produce uneven strip thickening.
- The thickening component is cellulose and slightly lignin.
- Therefore, the inner wall of the anther is also called the fibrous layer.
- The inner cells of the anther is the junction of the two pollen sacs on the same side, the cell wall is thickened without strips, and the tension generated is always maintained to make the anthers form longitudinal cracks at the parenchyma cells, and the pollen is scattered.
- In some plants with dehisced anther holes and closed flowers fertilized, the inner wall of the atherium does not undergo strip thickening.
3. Middle layer:
- When the sporogenous cells in the pollen sac develop into pollen mother cells, and then enter meiosis, the storage material in the middle layer is absorbed.
- Due to the extrusion caused by the proliferation and volume expansion of the cells in the pollen sac, the middle layer cells are flattened.
- When the anthers are mature, the middle layer has been absorbed, disintegrated and disappeared.
- In a few plants such as lily, the cell wall of the middle layer of the anther has a certain degree of strip thickening, so when it matures, the middle layer is still partially retained.
- The tapetum is the innermost layer of the anther wall and has a unique secretory function, which is essential for the development of pollen grains.
- Tapetum cells are larger, with abundant organelles, with mononucleate in the initial stage, and then mitoses without the formation of new walls, so they become binucleate, multinucleate, or polyploid cells.
- These characteristics indicate that the tapetum has a high degree of physiological activity.
- In addition, cells contain more RNA, protein and enzymes, and substances such as lipids, carotene and sporopollenin.
- The substances in the tapetum provide an important role in the development of pollen grains: the secreted callose enzymes can decompose the pollen mother cell and the callose wall of the tetrad in a timely manner so that the microspores are separated from each other; the synthesized proteins are transported to the pollen Wall, becomes pollen outer wall protein, and plays a role in the mutual recognition with pistil stigma; the synthesized sporopollenin forms the pollen grain wall material, which has the characteristics of hard and strong resistance.
- If the tapetum develops abnormally, male infertility often occurs breeding phenomenon.
Frequently Asked Questions on Anther:
1. What is anther and its function?
Answer: Anthers is a male reproductive whorl of flower they carry pollen, which is usually yellow in color and supported by thread-like structures called filaments. Production and development of pollen grain is main function of anther.
2. What does an anther mean?
Anther: Anther is Part of the stamen of flowers, which forms a small, single or double sac, where pollen grains is produced and stored.
3. What is the part of the flower that contains the pollen called?
Answer: Androecium is formed by the stamens, which in the anther pollen grains are produce.
4. What does the anther store?