Question

What is the function of a germ pore in a pollen grain?

Answer 1

The haploid microspores formed from a single microspore mother cell (pollen mother cell) are arranged in the form of four cells called microspore tetrad that are haploid. As the anthers mature and dehydrate, the microspores dissociate from each other and develop into pollen grains. These pollen grains are released with the dehiscence of another.

Complete answer:
The pollen grains represent the male gametophytes. These are generally spherical structures that have a measurement of around 25-50 micrometers in diameter. The cell wall of pollen grain is called sporoderm which consists of two layers i.e., exine and intine.
The exine is a tough outer layer made from sporopollenin. Sporopollenin is one of the most resistant organic materials known in the world. It can tolerate heat, strong acids as well as alkali. No enzyme that degrades sporopollenin is thus far known. This also helps in fossilization. Pollen grains are well-preserved as fossils because of the presence of sporopollenin. It is hard so that the pollen grains are well protected from hazardous environments when they are pollinated by biotic or abiotic agents. It exhibits a fascinating array of patterns and designs which is of taxonomic significance. It has prominent apertures called germ pores where sporopollenin is absent. The germ pore plays a paramount function in plant fertilization. It assists in the formation of pollen tubes and delivers male gametes during the process of fertilization.
Intine is the inner wall which is thin and continuous and made up of cellulose and pectin. Cytoplasm of pollen grain is surrounded by a cell wall.
The period that the pollen grains retain the power to germinate on landing on the stigma is named as pollen viability. It is highly fluctuating and depends on prevailing temperature and humidity. Pollen viability periods in plants like rice, wheat is 30 minutes and in plants of certain families like Leguminosae, Rosaceae and Solanaceae is several months.

Note:
Pollen allergy is a severe form of allergy caused by many species of pollen grains that are usually dispersed by anemophilous flowers. They cause severe diseases and bronchial afflictions in some people often leading to chronic respiratory disorders like asthma and bronchitis.