Exine of pollen grains has prominent apertures where sporopollenin is absent are known as:

Germ pores

The correct answer is Option (2) → Germ pores

Pollen grains are generally spherical measuring about 25-50 micrometers in diameter. It has a prominent two-layered wall.The inner wall of the pollen grain is called the intine. It is a thin and continuous layer made up of cellulose and pectin. The hard outer layer called the exine is made up of sporopollenin which is one of the most resistant organic material known. It can withstand high temperatures and strong acids and alkali. No enzyme that degrades sporopollenin is so far known. Pollen grain exine has prominent apertures called germ pores where sporopollenin is absent. Pollen grains are well- preserved as fossils because of the presence of sporopollenin. The exine exhibits a fascinating array of patterns and designs.

Pollen grain exine which are the outermost layer of the pollen wall has prominent apertures called germ pores where sporopollenin is absent. These apertures are crucial for the reproductive process of plants, particularly in the initiation of the pollen tube and the release of male gametes (sperm cells) during fertilization. When a pollen grain lands on the stigma of a compatible flower, it needs to germinate and develop a pollen tube to reach the ovule and deliver its genetic material. The initiation of the pollen tube growth is facilitated by the germ pores. These openings provide a point of entry for the pollen tube to emerge from the pollen grain.

Once the pollen tube emerges, it grows through the style of the flower, guided by chemical signals, towards the ovule. During this process, the male gametes housed within the pollen grain are released through the germ pores into the pollen tube. The pollen tube serves as a conduit for the male gametes to reach the ovule, where fertilization occurs.