Q1 of 86 Page 153

Assertion (A): If the plant part moves in the direction of gravity, it is called positive geotropism.

Reason (R) : Stem shows positive geotropism

Assertion is correct. When the plant part moves in the direction of gravity i.e. root it is called positive geotropism. When the plant part shows its movement towards the stimulus it is called positive tropism.


But reason is incorrect because stem moves away from the earth’s gravity so it is called negative geotropism.

More from this chapter

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15

To which directional stimuli do (a) roots respond (b) shoots respond?

 16

Name the cell that surrounds the stoma.

 2

Assertion (A): The loss of excess water from the aerial parts of the plant in the form of water vapour is known as transpiration.

Reason (R) : Stomata of the leaf perform transpiration.

 1

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.’