Question

Why do the stems and roots of a plant show unilateral growth towards the fight and gravity of the earth respectively?

Answer 1

Plant movement

1. These are the changes in the plant position or movement in their parts due to some external stimulus.
2. The external stimulus can be any changes in the surrounding environment.
3. When the movement has a certain direction, either towards or opposite to the direction of the stimulus, then it is called a tropic movement.

Phototropic and geotropic movement:

1. The movement of the plant part in response to light and gravity is called phototropic movement and geotropic movement.
2. If the plant receives sunlight in one direction only, then it will bend in the same direction of the light as it is getting an equal amount of light from all the directions uniformly on its body.
3. Also, since gravity attracts the root from all directions uniformly then, it grows straight and deep into the soil.