Read the passage and answer the following questions:
A typical angiosperm anther is bilobed with each lobe having two theca, i.e., they are dithecous. The anther is a four-sided (tetragonal) structure consisting of four microsporangia located at the corners, two in each lobe. The microsporangia develop further and become pollen sacs. They extend longitudinally all through the length of an anther and are packed with pollen grains. In a transverse section, a typical microsporangium appears near circular in outline. It is generally surrounded by four wall layers. When the anther is young, a group of compactly arranged homogenous cells called the sporogenous tissue occupies the centre of each microsporangium. As the anther develops, the cells of the sporogenous tissue undergo meiotic divisions to form microspore tetrads. As the anthers mature and dehydrate, the microspores dissociate from each other and develop into pollen grains. Inside each microsporangium several thousands of microspores or pollen grains are formed that are released with the dehiscence of anther.
Match List-I with List-II:
| List-I | List-II |
| (A) Exine | (I) Thin and continuous layer made up of cellulose and pectin |
| (B) Intine | (II) Innermost wall layer that nourishes the developing pollen grains |
| (C) Germ pore | (III) Hard outer layer made up of sporopollenin |
| (D) Tapetum | (IV) Aperture on the pollen wall where sporopollenin is absent |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → A-III, B-I, C-IV, D-II
The pollen grain has a two-layered wall, the outer exine and the inner intine. The tapetum belongs to the anther: it is the innermost wall layer of the microsporangium.
(A) Exine — this matches (III) Hard outer layer made up of sporopollenin. Sporopollenin is one of the most resistant organic materials known, which is why pollen grains are well preserved as fossils.
(B) Intine — this matches (I) Thin and continuous layer made up of cellulose and pectin. It is the inner wall of the pollen grain.
(C) Germ pore — this matches (IV) Aperture on the pollen wall where sporopollenin is absent. Germ pores are prominent apertures in the exine.
(D) Tapetum — this matches (II) Innermost wall layer that nourishes the developing pollen grains. It is a wall layer of the microsporangium, not a layer of the pollen wall.
NCERT Extract:
Structure of microsporangium – “… The innermost wall layer is the tapetum. It nourishes the developing pollen grains. Cells of the tapetum possess dense cytoplasm and generally have more than one nucleus.”
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. … The inner wall of the pollen grain is called the intine. It is a thin and continuous layer made up of cellulose and pectin.”