How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?
The movement of leaves of the sensitive plant differs from the movement of a shoot towards light in the following ways:
First, the movement of sensitive plant leaves is independent of growth, whereas the movement of a shoot towards light is caused by growth. If the shoot is prevented from growing, it will not show any movement.
Second, the sensitive plant movement is an immediate response to touch and is very quick. On the other hand, the movement of a shoot towards light is a tropic movement that is much slower as it involves growth.
Third, in the sensitive plant, cells change shape by changing the amount of water in them, resulting in swelling or shrinking. In contrast, the shoot movement is a directional growth movement in response to the environmental trigger of light.
Explanation
The textbook clearly distinguishes between two types of plant movements: one dependent on growth (like shoots bending towards light - phototropism) and one independent of growth (like the sensitive plant's response to touch). The sensitive plant shows quick, immediate movement through cell shape changes via water movement, while tropic movements like phototropism are slower growth-related responses.