Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): The exine of a pollen grain can withstand high temperatures and strong acids and alkali.
Reason (R): The exine is made up of sporopollenin, one of the most resistant organic materials known.
In the light of the above statements, choose the most appropriate answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Both (A) and (R) are true and (R) is the correct explanation of (A).
A pollen grain has a two-layered wall. Its hard outer layer, the exine, is made of sporopollenin.
Assertion (A): The exine of a pollen grain can withstand high temperatures and strong acids and alkali. — True. A is about how tough the exine is. It survives heat, strong acids and alkali, and no enzyme that degrades it is known so far.
Reason (R): The exine is made up of sporopollenin, one of the most resistant organic materials known. — True. R is about what the exine is made of.
Why R explains A? The exine resists heat, acids and alkali because of the material it is made of. Sporopollenin is one of the most resistant organic materials known, so a layer built of it is not broken down by such conditions. R gives the cause of A, so R is the correct explanation of A.
NCERT Extract:
Stamen, Microsporangium and Pollen Grain – “… It has a prominent two-layered wall. 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.”