Question

The exine possesses one or more thin places known as
(a) Raphe
(b) Germ pores
(c) Hilum
(d) Endothecium

Answer 1

Explanation:

Wall of a pollen grain consists of two layers-outer exine and inner intine. Exine is the hard outer layer which is made up of sporopollenin. Sporopollenin is one of the most resistant organic material known. It can withstand high temperature, strong acid or alkali and is not degraded by enzymes. Because of the presence of sporopollenin, pollen grains are well preserved as fossils. At certain places the exine is thin or absent, these areas may have thickened intine of deposition of callose. They are called germ pores(if rounded) or germinal furrows(if elongated). Sporopollenin is absent in the region of germ pores or germinal furrows.

So, the correct answer is 'Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion'.

Answer 2

The exine possesses one or more thin places known as Germ pores.

What is exine?

• It is the outermost layer of the two primary layers that make up pollen grain walls.
• The exine layer is composed of sporopollenin, one of nature's most resistant compounds.

What is germ pore?

• The germ pores are structures in the pollen grain's exine layer that is devoid of sporopollenin.
• During the fertilisation process, the germ pore aids in the development of the pollen tube and the release of the male gametes.

Therefore, the thin places present in the exine are germ pores.