While conducting experiments to study the effect of various stimuli on the plants, it was observed that the roots of a plant X grow and bend towards two stimuli A and B but bend away from a third stimulus C. The stem of the plant X, however, bends away from stimuli A and B but bends towards the stimulus C. The stimulus B is known to act on the roots due to too much weight of the earth. Keeping these points in mind, answer the following question :

(b) Name the stimulus B.

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Solution

The stimulus B is gravity.

The movement of a plant part in response to gravity is called geotropism.

Roots show positive geotropism (grows towards force of gravity) whereas, stems show negative geotropism (grows against force of gravity).

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While conducting experiments to study the effect of various stimuli on the plants, it was observed that the roots of a plant X grow and bend towards two stimuli A and B but bend away from a third stimulus C. The stem of the plant X, however, bends away from stimuli A and B but bends towards the stimulus C. The stimulus B is known to act on the roots due to too much weight of the earth. Keeping these points in mind, answer the following questions :

(a) What could stimulus A be?

(b) Name the stimulus B.

(d) The branches of a fallen tree in a forest grow straight up in response to two stimuli. What could be these two stimuli out of A, B and C? Also, name these two stimuli.

Q. A student takes a potted plant growing in a transparent glass jar. This potted plant having straight stem and straight root is kept near the window in a dark room so that sunlight falls on it from the right side (through the window). After some days, it is found that the stem of plant bends towards the right side (from where the light is coming) but the root bends to the left side, away from the light.
(a) What term is used to indicate:
(i) response of plant to sunlight?
(ii) bending of stem of plant towards sunlight?
(iii) bending of root of plant away from sunlight?
(b) Name the plant hormone which makes the plant respond to sunlight.

In tropic movements, plant parts move

(a) away from the stimulus

(b) towards the stimulus

(d) only towards water

Q. A potted plant having straight parts A and B was placed horizontally on its side as shown in figure (i). After a few days it was observed that the parts A and B of the plant acquire new positions as shown in Figure (ii).
(a) Name the phenomenon exhibited by the position of plant parts A and B in Figure (ii)
(b) Name the stimulus (other than sunlight) which causes plant part A to grow and bend upwards, and plant part B to bend downwards.

Q. Sunlight is the stimulus and the bending of the plant towards it is the ______

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The stimulus B is gravity. The movement of a plant part in response to gravity is called geotropism. Roots show positive geotropism (grows towards force of gravity) whereas, stems show negative geotropism (grows against force of gravity).

The stimulus B is gravity.

The movement of a plant part in response to gravity is called geotropism.

Roots show positive geotropism (grows towards force of gravity) whereas, stems show negative geotropism (grows against force of gravity).