Question

Growth of pollen tube towards ovule is known as
A. Phototropism
B. Geotropism
C. Hydrotropism
D. Chemotropism

Answer 1

Hint: The pollen tube is a tubular structure created by the male gametophyte of a seed plant during germination. Elongation of the pollen tube is an important part of the plant's life cycle. The pollen tube acts as a conduit for transporting male gamete cells from the pollen grains to the pistil (in the case of flowering plants) to the egg at the base of the ovary.

Complete answer:
Phototropism-This type of movement is triggered by light. Not all plants and not all parts respond equally to these stimuli. Typically the stem grows and rotates towards the light source while the roots move away from the light source. Leaves also respond positively to light sources. However, the blade is in a position where the large surface of the blade is perpendicular to the beam. Therefore, the stem must be photo-positive, phototropic with a negative root, and a phototropic leaf or transverse degeneration of the foot. Phototropism is also known as heliotropism.
Geotropism- All responses to the stimulus of gravity are called geotropic. The effect of gravity on plants is long-term and permanent, so it cannot be compared with light and temperature. The main roots and some other parts of the root system tend to grow directly towards the center of gravity, which is why they are positively called geotropic.
Hydrotropism- Paratonic growth curves associated with water stimulation, such as the movement of the Drosera tentacles, the closure of the Nepenthes cover by the supply of nitrogen, and the invasion of parasites into the body of the Haustoria host, are called hydrotropic movements. The tropical response to water stimuli is called water release. The roots show a positive hydrotropic response. They leaned towards the water. Hydrotropism is fundamentally stronger than geotropism.
Chemotropism- Certain chemicals are responsible for the bending of plant organs. Chemicals in the environment have a direct effect on the growth of certain plant structures. A classic example is the growth of pollen tubes through stigma and germ cell strength. The chemicals present in carpels are believed to be the main force behind the growth of the pollen tube. Calcium and boron are the main chemicals responsible for this movement.
So, the correct answer is “Option D”.

Note:
When pollen grains germinate from the food jelly using stamped pieces, the pollen production tubes grow in the air and travel to the stamp pieces. The pollen tube shows negative tropism from the air and positive chemotropism. The first arrangement of the pollen tubes emerging from the stigma is hydrodynamic (hydrotropism) followed by mechanical conduction along the mucous pathways. In the second half of the forceful movement of the pollen tube, there is no doubt that the direction of the chemotropic orientation is the cause (Schneider, 1956).