Question

The growth of a pollen tube towards ovule is caused by
A. Phototropism
B. Hydrotropism
C. Gravitropism
D. Chemotropism

Answer 1

Hint: Sexual propagation of flowering plants depends on the transfer of the sperm to the egg, which happens through a long, polarized step of a pollen chamber, described the pollen tube. The pollen tube produces particularly at its apex, and this growth is characterised by very quick rates and ends at wide lengths.

Complete Answer:
Let us analyse the given options, to find out the correct answer.
Option A: Phototropism is the response of a plan to light. Phototropism is most frequently seen in plants, but can also happen in other bions such as moulds. The cells on the plant that are distant from the light have a substance called auxin that responds when phototropism transpires. Therefore, this is an incorrect option.

Option B: Hydrotropism is a plant's growth reaction in which the path of growth is limited by a motive or pitch in water absorption. A typical example is a plant root growing in wet air leaning near a higher relative moisture level. Therefore, this is an incorrect option.

Option C: Gravitropism is a coordinated method of differential germination by a plant or mould in response to gravity pulling on it. Gravity can be unless "natural gravity" or “artificial” gravity. It is a common characteristic of all higher and many lower plants as well as other bions. Therefore, this is an incorrect option.

Option D: For fertilization, pollen grains develop a chemotropic mechanism where the maturity of the pollen tube is towards the ovules. During propagation, ovaries deliver chemicals that trigger the chemotropic reaction from growing pollen tubes. Therefore, this is the correct option.

Thus, option D is the correct answer.

Note: Chemotropism is described as the growth of bions driven by chemical provocations from outside of the bion. It has been seen in plants, bacteria and moulds. A chemical pitch can impact the growth of the bion in a positive or negative way.