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Question : 9
Total: 12
(a) Some plants like pea plants have tendrils which help them to climb up other plants. Explain how is it done. Name the plant hormone responsible for this movement.
OR
(b) Name the phenomenon occurring in plants which are under the control of gravity, water and chemicals with one example each that shows the movement involved.
OR
(b) Name the phenomenon occurring in plants which are under the control of gravity, water and chemicals with one example each that shows the movement involved.
Solution:
(a) A tendril is a slender stem- or petiolelike structure that is used by vines and climbing plants to wrap around or to hook a support. Auxin is a growth hormone which is generally synthesised at the shoot tip. It enhances the growth of cells so that plants can increase their length. As soon as the tendril comes in contact with any support system, auxin stimulates the cell to grow faster on the opposite side, as a result the tendril forms a coil around the support.
OR
(b) In response to gravity the roots of a plant always grow downwards. This phenomenon is known as geotropism. In response to water, a plant root always moves toward it. This phenomenon is known as positive hydrotropism. The growth of pollen tube towards the ovule is caused in response to a chemical stimulus i.e., the chemicals released by the ovule during the time of fertilization, shows chemotropism.
OR
(b) In response to gravity the roots of a plant always grow downwards. This phenomenon is known as geotropism. In response to water, a plant root always moves toward it. This phenomenon is known as positive hydrotropism. The growth of pollen tube towards the ovule is caused in response to a chemical stimulus i.e., the chemicals released by the ovule during the time of fertilization, shows chemotropism.
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