POLLEN GRAINS

Pollen is a mass of microspores found in seed plants that appears as fine dust. Each pollen grain is a tiny body of different shape and structure that forms in the male structures of seed-bearing plants and is transferred to the female structures by various mechanisms (wind, water, etc.) where fertilization takes place. Pollen is produced by the anthers of the stamens in flowers in angiosperms. It is generated in the microsporophylls of the microstrobili (male pollen cones) of gymnosperms. One or more vegetative cells and a reproductive cell make up pollen. The male gamete is not found in a pollen grain. The vegetative cell generates the pollen tube that expands to meet the unfertilized ovules in angiosperms and certain gymnosperms, and the reproductive cell is the source of sperm.

Pollen grains Structure

Microsporogenesis is the process through which pollen grains are produced. Which division in the anthers’ locules produces pollen grains? Pollen grains grow by meiosis division of pollen cells. The microspores are subsequently separated from the tetrads, and pollen grains are formed as a result of these separations. One or more vegetative cells and the male gamete cell make up the morphological structure of pollen grains. The mature pollen grain grows at varied rates, resulting in a variety of cell counts and types. Only two cells make up a mature pollen grain: a pollen tube cell and a generative cell. When the pollen tube cell germinates, it becomes a pollen tube, and the generative cell travels to the plant’s ovaries. 

Pollen grains are generated through a process known as microsporogenesis. Pollen grains are produced by which division of the anthers’ locules? Pollen grains are formed when pollen cells divide through meiosis. Following that, the microspores are separated from the tetrads, and pollen grains are generated as a result of the separations. The morphological structure of pollen grains is made up of one or more vegetative cells and the male gamete cell. Pollen grains mature at different rates, resulting in a wide range of cell counts and kinds. A mature pollen grain is made up of only two cells: a pollen tube cell and a generative cell. The pollen tube cell develops a pollen tube once it germinates, and the generative cell travels to the plant’s ovaries.

Types of Pollen Grains

Pollen grains can be generated in a variety of ways. The orientation of the furrows about the original tetrads from the microspores can be used to classify pollen grains. These can be sulcate or colpate. The furrow in the Sulcate runs across the centre. The monosulcate sulcus is one, the bisulcate sulcus is two, and the polysulfate sulcus is more than two. A furrow runs through the colpate in places other than the centre of the outer face. They are syncopated if they have two or more fused ends, and polysorbate if they do not have two or more fused ends. Certain pollen grains may be tricolpate pollen grains. This indicates that they have three colpi or have a morphology that is comparable to tricolpate pollen.

Pollination in Angiosperms

Pollination in angiosperms is the transfer of pollen grains from one plant’s anther to the stigma of another plant of the same species. This suggests that angiosperms are cross-pollinated as well as self-pollinated. Self-pollination occurs when flowers fertilise each other (the same flower on the same plant), but cross-pollination occurs when pollen grains from another bloom pollinate the flower of a different plant. Pollen grain movement is typically accomplished through the use of biotic agents like wind, water, or animals – primarily insects and birds. In terms of pollen grain structure, when pollen grains do not separate in tetrads, they form complex pollen grains. These are pollen grains found in angiosperms.

Preservation

Pollen grains have a high level of resilience to attack. They are ubiquitous elements of geological sediments because they are spread by winds and produced in large quantities by plants. Pollen grains have offered a wealth of information about the genesis and history of terrestrial plant life due to their remarkable resistance to degradation and long-lasting nature. Pollen grains also have a symmetrical structure that may be seen under a microscope and can be used as a taxonomic aid. The structure of pollen grains is unique, and pollen grains alone can be used to identify species. Palynology is the study of pollen grains, and pollen grains can be used to identify all angiosperm pollen and gymnosperm families.

CONCLUSION

Pollen grains are small particles that contain androecium — a flower’s male reproductive organ. The center of the pollen grain comprises cytoplasm as well as the tube cell, which changes into a pollen tube, and the generative cell, which releases the sperm nuclei.

Pollen is produced in such large amounts that it contributes significantly to the airborne constituents of the Earth’s atmosphere, particularly over continents. The proteinaceous material found in many pollen grains (namely, ragweed and many types of grass) causes an allergic reaction known as hay fever.