Question

In a pollen grain, larger nucleus is
A. generative nucleus
B. tube nucleus
C. vegetative nucleus
D. none of the above

Answer 1

Hint: Pollen grains represent the male cell, which are produced by the anthers of male reproductive part which are present in flowers. Pollen grains contain immature male gametophytes that contain hereditary material, which fuse with the female egg and cause fertilization.

Complete answer:
Pollen grain present in the anthers which are pollen sac or microsporangia. Microsporangium is the future pollen sac that consists of two parts known as outer wall and inner sporogenous tissue. The development of pollen grain is said to be microsporogenesis. The sporogenous tissue changes into microspore or pollen mother cells.

The pollen grain or microspore is represent the immature male gametophyte, which grow in size and inflow the nutrients, vacuole push the nucleus near the wall side, after that protoplast divides mitotically and form two unequal cells named as small generative cell and other is larger tube or vegetative cell. Callose layer is developed around the generative cell to separate the cell from the pollen grain wall. At the time of pollination the pollen grain is either 2-cell, one generative and one vegetative in most of the angiospermic plants. 3 single tube cells with two vegetative cells.

The larger nucleus is in the vegetative cell that helps in development of pollen grains while smaller in generative cells, which fuse with egg. The tube nucleus guides or controls the growth of pollen tube and cells follow the path of the tube nucleus.

Hence, the correct answer is option (B).

Note: The pollen grain wall is called sporoderm, which is consist of two layer outer called exine and inner is intine, exine is made up of sporopollenin substance which is highly resistive in nature and not degraded easily by any substance can withstand adverse environment for thousands of year.