Q1 of 86 Page 153

There are 3 plants A, B and C. The flowers of A open their petals in bright light during the day but close them when it gets dark at night. On the other hand, the flowers of plant B open their petals at night but close them during the day when there is bright light. The leaves of plant C fold up and droop when touched when fingers or any other solid object.

a) Name the phenomenon shown by the flowers of plant A and B.


b) Name one flower each which behaves like the flowers of plant A and B.


c) Name the phenomenon exhibited by the leaves of plant C.


d) Name a plant whose leaves behave like those of plant C.’

a. The flowers show nastic movements i.e. photonasty. These are non-directional movement caused by stimulus light.


b. Dandelion flower [ Taraxacum officinale ] opens up in the morning in bright light while closes its petal in dark or night time. Moon flower [ Ipomoea alba ] opens its petals at night and closes during day time.


c. The leaves of plant C exhibit seismonasty or thigmonasty. These are non-directional movements which occur in response to touch and these are very quick.


d. Mimosa pudica [touch-me-not] plant, leaves droop down immediately when slightly touched due to change in turgor pressure.


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