Which of the following statements are incorrect?
(A) In plants that shed pollen at the two-celled stage, the generative cell divides to form the two male gametes before the pollen is shed.
(B) The vegetative cell of a pollen grain is bigger than the generative cell and has abundant food reserve.
(C) In some members of Rosaceae, Leguminoseae and Solanaceae, pollen grains maintain viability for months.
(D) The intine of a pollen grain is made up of cellulose and pectin.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → A only
A mature pollen grain has a large vegetative cell and a small generative cell. The generative cell gives rise to the two male gametes, either before the pollen is shed (3-celled stage) or later, during the growth of the pollen tube (when pollen is shed at the 2-celled stage).
(A) In plants that shed pollen at the two-celled stage, the generative cell divides to form the two male gametes before the pollen is shed. — False. In such plants the generative cell divides during the growth of the pollen tube in the stigma, after the pollen has been shed.
(B) The vegetative cell of a pollen grain is bigger than the generative cell and has abundant food reserve. — True. The vegetative cell also has a large, irregularly shaped nucleus. The generative cell is small and floats in its cytoplasm.
(C) In some members of Rosaceae, Leguminoseae and Solanaceae, pollen grains maintain viability for months. — True. Viability is highly variable. In rice and wheat it is lost within about 30 minutes, but in these families it lasts for months.
(D) The intine of a pollen grain is made up of cellulose and pectin. — True. The intine is the thin, continuous inner wall of the pollen grain.
So only A is incorrect.
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. When the pollen grain is mature it contains two cells, the vegetative cell and generative cell (Figure 1.5b). The vegetative cell is bigger, has abundant food reserve and a large irregularly shaped nucleus.”
Stamen, Microsporangium and Pollen Grain – “… In some cereals such as rice and wheat, pollen grains lose viability within 30 minutes of their release, and in some members of Rosaceae, Leguminoseae and Solanaceae, they maintain viability for months.”
Pollination – “… You would recall that in some plants, pollen grains are shed at two-celled condition (a vegetative cell and a generative cell). In such plants, the generative cell divides and forms the two male gametes during the growth of pollen tube in the stigma.”