Question

Which one of the following statements is wrong regarding pollen grains?

• A. Vegetative cell is larger than generative cell
• B. When pollen is shed at the two-­celled stage, double fertilization does not take place
• C. Intine is made up of cellulose and pectin
• D. Pollen grains in some plants remain viable for months

Answer 1

The correct option is B

When pollen is shed at the two-­celled stage, double fertilization does not take place

The correct option is B.

Explanation for the correct option:

1. The pollen grains represent the male gametophytes.
2. The vegetative cell and the generative cell are both present in the mature pollen grain.
3. The vegetative cell is larger, has a huge, atypically formed nucleus, and an ample food supply.
4. Small and floating in the cytoplasm of the vegetative cell is the generative cell.
5. It has a spindle-shaped body, a nucleus, and a lot of cytoplasm.
6. Pollen grains in more than 60% of angiosperms are shed at the two-­celled stage but double fertilisation occurs in them.
7. Double fertilization is the union of two male gametes and a female gametophyte.
8. The process starts when a pollen grain clings to the stigma of the carpel, a flower's female reproductive organ.

Explanation for the incorrect options:

Option $\mathrm{A}$:

1. Cellular differentiation between generative and vegetative cells results from an unequal cell division during pollen formation, which is necessary for sexual plant reproduction.
2. A gametophyte cell, an expanded pollen tube that transports male gametes to the embryo sac, is produced by the larger vegetative cell.
3. In contrast, the smaller generative cell produces two sperm cells or male gametes.

Option $\mathrm{C}$:

1. The intine and exine layers of the pollen grains are thick, with at least a two-layered wall.
2. The intine is pectocellulosic in nature.
3. The extremely decay-resistant chemical sporopollenin makes up the exine or outer coat of the organism.
4. One or two of the tiny portions or pores of the exine usually grow into pollen tubes, and the thick portion of the exine is sometimes extensively sculpted.

Option $\mathrm{D}$:

1. Each pollen grain has a different level of viability.
2. Liquid nitrogen is used to keep pollen grains safe.
3. Because pollen grains may be preserved in liquid nitrogen for a more extended period of time in pollen banks, many rare species can be preserved using this technique.

Final answer: The wrong statement regarding pollen grains is when pollen is shed at the two-­celled stage, double fertilization does not take place.