Question

What happens in the following cases and give reasons:

A- growth of seedling in horizontal position

B- cut the cleoptile of a plant

Answer 1

What happens in the following cases and give reasons:

A- Growth of seedling in horizontal position

Germination takes place in a manner where the roots grow downwards and the shoot upwards, when this germinating seeds are turned horizontal then too the shoot will grow upwards and the root will turn and grow downwards this is called tropism and this is due to the stimulus.

Roots are positively geotropism and shoots are negatively geotropism, geotropism is the plants response to the gravity. This mechanism is same as the phototropism. Due to gravity the auxin of the plants migrates in the stems to the lower side and thus the hormones stimulates the growth of the stem upwards.

B- Cut the cleoptile of a plant

The pointed protective sheath that covers the emerging shoot is the coleoptiles in the plant. In phototropism experiment it is proved that plants grown towards the light, this response were due to the chemical that comes from the coleoptiles tip in the plant. If the coleoptiles of the plant were cut down then the plant will stop growing.