Module: | Double Fertilization & Endosperm
Q81: Consider the following statements regarding the formation of callose plugs in the pollen tube:
1. As the pollen tube elongates through the style, it periodically forms transverse callose plugs behind the growing apex.
2. The primary biological function of these plugs is to isolate the active cytoplasm and male gametes at the extreme tip of the tube.
3. These callose plugs are actively synthesized and secreted by the surrounding stylar cells to physically push the pollen tube forward.
Which of the above statements is/are correct?
2. The primary biological function of these plugs is to isolate the active cytoplasm and male gametes at the extreme tip of the tube.
3. These callose plugs are actively synthesized and secreted by the surrounding stylar cells to physically push the pollen tube forward.
Which of the above statements is/are correct?
✅ Correct Answer: A
The correct option is A. Statements 1 and 2 are correct, whereas Statement 3 is strictly incorrect.
The pollen tube is an incredibly long, highly vacuolated cell.
As it grows rapidly down the style, the living cytoplasm, the vegetative nucleus, and the two male gametes must remain strictly at the growing tip.
To achieve this causally, the vegetative cell cytoplasm periodically synthesizes and deposits transverse walls made of callose (a beta-glucan polymer) just behind the moving cytoplasm.
These are called callose plugs.
They structurally seal off the older, empty parts of the tube, preventing the vital contents from flowing backward.
Statement 3 presents a physiological falsehood.
The stylar cells do not synthesize these plugs; they are entirely an endogenous product of the pollen tube's own metabolic machinery to manage its massive internal volume during extreme elongation.
The pollen tube is an incredibly long, highly vacuolated cell.
As it grows rapidly down the style, the living cytoplasm, the vegetative nucleus, and the two male gametes must remain strictly at the growing tip.
To achieve this causally, the vegetative cell cytoplasm periodically synthesizes and deposits transverse walls made of callose (a beta-glucan polymer) just behind the moving cytoplasm.
These are called callose plugs.
They structurally seal off the older, empty parts of the tube, preventing the vital contents from flowing backward.
Statement 3 presents a physiological falsehood.
The stylar cells do not synthesize these plugs; they are entirely an endogenous product of the pollen tube's own metabolic machinery to manage its massive internal volume during extreme elongation.