NEET BIOLOGY

Detailed explanation-1: -The non-directional movement of a plant part, usually the petals of flowers, in response to light is called photonastic movement. For example, leaves of Oxalis triangularis open in bright light and droop in dim light. Thermonastic movements in plants occur due to the change in temperature.

Detailed explanation-2: -Photonasty Movement: The non-directional movement of a plant part usually in the petals of flowers in response to light is photonasty movement. The stimulus in Photonasty is light. Many petals of flowers open in the daylight and closed in the evening in response to the intensity of light.

Detailed explanation-3: -Phototropism is the movement of plants towards or away from light. If the plant part moves towards the light it is called as positive phototropism. If the plant part moves away from the light it is called as negative phototropism.

Detailed explanation-4: -The non-directional movement of petals of flowers in response to light is called photonasty. For example, a dandelion flower opens in the morning due to bright light and closes in the evening when the light fades.

Detailed explanation-5: -They open or unfold with sunrise (photonasty) and close or fold with sunset (nyctinasty). These diurnal movements are common in compound leaves of members of Fabaceae and Oxalidaceae. Flowers of tulip (Tulipa spp.) close their petals at night and open them in the morning.