Question

Describe the structure of pollen grain of angiosperms

Answer 1

Pollen grains represent the male gametophyte. When the anther undergoes maturation and anther dehydrates, the microspores dissociate from one another and become pollen grains. Inside each and single microsporangium, several thousand which are very large in number of microspores or pollen grains are formed that are released with the dehiscence of anther. Pollen grains are usually male gametes.

Complete answer:
1.The pollen grains represent the male gametophytes
2.These are generally spherical structures measuring about 25-50 micrometre in diameter
3.The cell membrane of pollen grain is named sporoderm which consists of two layers., i.e., exine and intine

Exine: It's a hard outer layer made from sporopollenin (one of the foremost resistant organic materials known). The layer exine protective because it can withstand heat , strong acids and alkali. No enzyme that degrades sporopollenin is thus far known.
This also helps in fossilization. Pollen grains are often preserved and may be studied as fossils due to the presence of sporopollenin.
It is hard in order that the pollen grains remain protected and sealed from hazardous environment once
They are pollinated by biotic/abiotic agents it exhibits a desirable array of patterns and styles which is of taxonomic significance
It has prominent apertures called germ-pores where sporopollenin is absent.

Intine: it's the inner wall which is thin and continuous and made from cellulose and pectin.
Cytoplasm of pollen grain is surrounded by a cell wall.

Note: Pollen grains of the many species (especially anemophilous plants) cause severe allergies and bronchial afflictions in some people often resulting in chronic respiratory disorders like asthma and bronchitis. Pollen grains are rich in nutrients. They increase performance of athletes.