Read the passage given below and answer the following question.
The pollen grains serve as the male gametophytes in flowering plants. Upon touching the opened anthers of flowers like Hibiscus, one can observe the deposition of yellowish powdery pollen grains on their fingers. When these grains are sprinkled on a glass slide with a drop of water and observed under a microscope, a fascinating variety of architecture, including sizes, shapes, colours, and designs, can be seen among the pollen grains from different species. Pollen grains are generally spherical and have a diameter ranging from 25 to 50 micrometers. They possess a two-layered wall, with the outer layer composed of sporopollenin, which exhibits intricate patterns and designs. The inner wall of the pollen grain is a thin and continuous layer. When mature, the pollen grain contains two cells: the larger vegetative cell and the smaller generative cell. The vegetative cell holds abundant food reserves and a large, irregularly shaped nucleus, while the generative cell floats within the cytoplasm of the vegetative cell. In the majority of angiosperms (over 60 per cent), pollen grains are shed at the 2-celled stage, where they contain vegetative and generative cells. However, in the remaining species, the generative cell undergoes mitotic division to produce the two male gametes before the pollen grains are shed, resulting in a 3-celled stage.
The intine of pollen grains is made up of which of the following substances?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Both (1) and (2)
The pollen grain wall has two layers. The outer exine is made of sporopollenin. The inner layer, the intine, is a thin and continuous layer made of two substances: cellulose and pectin. So the answer must include both.
Option (1) Cellulose — Correct statement, but it is only one of the correct points, so on its own it is not the answer. Cellulose is one of the two substances of the intine, but the intine also has pectin.
Option (2) Pectin — Correct statement, but it is only one of the correct points, so on its own it is not the answer. Pectin is the other substance of the intine, but naming it alone leaves out cellulose.
NCERT Extract:
Stamen, Microsporangium and Pollen Grain – “… 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 cytoplasm of pollen grain is surrounded by a plasma membrane.”