Question

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

Answer 1

Hint: Pollen grain gives rise to the tube of pollen that absorbs nourishment for its production from the style cells. To give birth to two male gametes, generative cells divide. A generative cell and a vegetative cell are present in each mature pollen grain in angiosperms.

Complete answer:
According to point (a)- During pollen growth, cellular differentiation of a generative and a vegetative cell is necessary for sexual plant reproduction and is triggered by an unequal division of cells. Two sperm cells, or male gametes, are formed by the smaller generative cell, while the larger vegetative cell creates an elongated pollen tube, a gametophyte cell, to carry the male gametes to the embryo sac.
According to point (b)- Not all pollen grains remain viable for the same period of time. They store pollen grains in liquid nitrogen. In pollen banks, pollen grains can be preserved in liquid nitrogen for a longer period of time and a large number of rare species can be stored through this process.
Intine is made up of cellulose and pectin- A dense wall of at least two layers, the intine and the exine, grows into the pollen grains. The intestine consists mostly of cellulose and pectin, or inner layer. The exine, or outer layer, is composed of a chemical called sporopollenin, which is extremely decay-resistant. The exine typically has one or two thin areas or pores from which the pollen tubes germinate and usually the thick region of the exine is strongly sculpted.
According to point (d)- The pollen grains are shed at the double-celled stage in most flowering plants. In addition, stigma occurs in the growth of male gametophytes. Pollen grain gives rise to the tube of pollen that absorbs nourishment for its production from the style cells. To give birth to two male gametes, generative cells divide. Of these, one fuses to form a diploid zygote with the egg, while the second male gamete fuses to form a primary endosperm nucleus with the two haploid polar nuclei or diploid secondary nucleus of the central cell. In the same embryo sac, these two actions of fertilisation occur and are referred to as double fertilisation.

Hence, the correct answer is (D).

Note:
In the beginning, pollen grain protoplasts in an uninucleated state, but at the time of release, it becomes 2-3 celled. The pollen grain nucleus is actually increasing in size and moving to one side of the wall. The protoplast then separates generative cells and tube or vegetative cells to create two unequal cells.