The non-directional movement of a plant part (usually petals of flowers) in response to light is called photonasty. In other words, photonasty is the nastic movement of a plant part )like petals of flowers. in response to light. Thus, the stimulus in photonasty is light. A dandelion flower opens up in the morning in bright light but closes in the evening when the light fades and it gets dark. The opening and closing of petals of dandelion flowers in response to the intensity of light is an example of nastic movement in which the stimulus is light. In other words, it is an example of photonasty. The moonflower behaves exactly opposite to that of dandelion flowers in respect of response to light. The petals of moonflower close during the day when there is bright light but open up at night when it is dark and there is no light I This is also an example of photonasty.
1. The non-directional movement of a plant part )usually petals of flowers. in response to light is called ________.
(i) Thigmonasty
(ii) Photonasty
2. State true or false. Opening and closing of flowers in response to light (or photonasty) are growth movements.
(i) TRUE
(ii) FALSE
3. Moonflower ______ the petals during the daytime when there is bright light
(i) Closes
(ii) Opens
4. Moonflower _______ the petals at dusk (or night) when it gets dark and there is no light.
(i) Closes
(ii) Opens
5. Dandelion flower ________ the petals at dusk )or night. when it gets dark.
(i) Closes
(ii) Opens
