Question

Growth of pollen tube is
A) Apical
B) Basal
C) Intercalary
D) Diffused

Answer 1

Pollen tube is a tube like structure which is formed on the male reproductive organ stigma, exits through the germ pore and passes down the style to the female reproductive organ pistil.

Complete answer:
Let us analyse the options to find the correct answer.

Option A: Pollen tube grows at the tip of stigma at a very fast rate. Thus the growth is apical and takes solace due to fusion of apical vesicles. Pollen tube growth is a type of polarized cell elongation which helps in the transport of sperm cells to the embryo sac. The components of vesicles at the pollen tube tip consist of cell wall material fuses with the plasma membrane of apex providing cell membrane and cell wall content for the growing tube. Pollen tubes tip also provide the location where cues are obtained for directional growth. Hence, this is the correct option.
Option B: The pollen tube growth is not basal. Hence, this is an incorrect option.
Option C: There is no intercalary meristem in the pollen tube, henec intercalary growth is not possible. Hence, this is an incorrect option.
Option D: Pollen tube growth occurs in only one direction i.e downward. The growth occurs in a very small region only and is not spread out. Also, it's a chemotrophic growth. Hence, this is an incorrect option.

Hence the correct answer is option ‘A’.

Note: Sexual reproduction of plants is dependent on the transfer of sperms to the egg present in the ovary via a long tubular channel called pollen tube.Apical calcium concentration is increased at the growing tip during pollen tube growth. Actin also helps in the polarized growth of pollen tubes.