Question

Assertion: Pollen gain can be well preserved and used as microfossils.
Reason: In certain places on pollen grains exine is absent and they have a thick layer of intine at these places.
A) Both Assertion and reason are correct and reason is the correct explanation for assertion.
B) Both Assertion and reason are correct but reason is not the correct explanation for assertion.
C) Assertion is correct but reason is incorrect.
D) Both Assertion and reason are incorrect.

Answer 1

Hint:-Pollen grains are powdery microscopic structures which carry the male microgametophytes of flowering plants for the process of fertilization. It contains cytoplasm along with the tube cell (which later differentiates into the pollen tube) and the generative cell (which releases the sperm nuclei).

Complete Answer:-Wall of a pollen grain consists of two layers, the outer layer is called exine and the inner layer is called intine Exine is hard in nature which is made up of sporopollenin. Therefore It can withstand extreme temperatures, strong acids or alkalis and enzymes. Therefore Pollen grains can be well preserved and are used as microfossils due to the presence of sporopollenin. It contributes to the formation of its outer layer exine and is the most stable and non-degraded and highly resistant organic material known in the world.
In certain places on pollen grains exine is absent or thin and a thick layer of intine (with callose deposition) is present. These places are known as germ pore or germ furrows through which pollen tubes emerge during the process of fertilization.

Hence, the correct option is (B) Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.

Note:- Sporopollenin is a cross-linked polymer made up of carbon, hydrogen, and oxygen that is stable and has been found chemically intact in forms of sedimentary rocks over 500 million years old. Sporopollenin is absent in the region of germ pores or germinal furrows which allows the emergence of pollen tubes carrying the male gamete for fertilization towards the female gamete in the ovary.