What are Pollen Grains?

Pollen grains in flower are microscopic structures that produce male gametes for sexual reproduction in seed plants. Pollen grains are produced in the anthers. Each pollen grain is a single cell that contains two male gametes. Pollen grains are classified by the orientation of the furrows about the original tetrads from the microspores. They can be sulcate or colpate.

Pollen grains are formed by meiotic division in the locules of anthers. The process of forming pollen grains is called microgametogenesis. Pollen grains are commonly round, ovule, triangular, disc, or bean-shaped. They can be white, yellow, orange, or cream in color, depending on the plant species.

Pollen Grains Structure

Pollen grains are tiny, powdery structures that contain male gametes and are produced by most flowering plants. They have a hard outer layer called the exine, which is made of sporopollenin. The inner layer of the pollen grain is called the intine, and is made of cellulose and pectin. The central part of the pollen grain is the cytoplasm, which contains nuclei that are responsible for fertilization. 

The germination of pollen grains marks the beginning of the reproductive process in flowering plants, initiating the growth of pollen tubes for fertilization. Each pollen grain contains vegetative (non-reproductive) cells and a generative (reproductive) cell. In flowering plants, vegetative cells produce pollen tubes, which divide to form two sperm nuclei. When pollen lands on a pistil or female cone, pollen germinates and forms pollen tubes. It transfers sperm to the ovule, which contains the female gametophyte.

Also Read: Difference Between Pollination and Fertilization 

Function of Pollen Grain

Pollen grains are essential for reproduction in both gymnosperms and angiosperms. They play a key role in plant growth by transmitting male genetic material. Various functions of the pollen grain are:

• Pollen grains transfer male gametes to female gametes, which are the eggs of the embryo sac. This promotes the sexual reproduction of the plant.
• In cross-pollination, pollen is used to transfer haploid male genetic material from the anther of a single flower to the stigma of another. 
• In self-pollination, this process takes place from the anther of a flower to the stigma of the same flower.
• Pollen grains facilitate the fertilization of the ovum, which is contained within the ovule, the female reproductive organ in plants.
• Pollen grains play a key role in plant growth by transmitting male genetic material.
• Pollen is also infrequently used as food and food supplement. It is recognized as an excellent dietary supplement for human nutrition.

Also Read: Difference between Angiosperms and Gymnosperms

Microspores and pollen grains are two structures that develop during the two phases of plant reproduction – the sporophytic and gametophytic stages. Microspores are produced by the endothecium of anther and develop into pollen grains. The structure of pollen grains includes an outer layer called the exine and an inner layer called the intine.

Pollen grains are larger, more complex structures that contain the male gametophyte. Microspores are found in both seedless and seed plants, while pollen grains are found only in seed plants. In this article, we will look into the differences between microspores and pollen grains.