Plant Hormones and Reflex Actions: Questions and Answers

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1. What are plant hormones?


Plant hormones are fluids secreted within the plant, also known as phytohormones. They regulate the growth and development of the plant. Examples of plant hormones are auxin and gibberellins.

2. How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?


The movements of the leaves of the sensitive plant are touch-sensitive and independent of growth, while the movement of the shoot towards light is growth-related and known as phototropism.

3. Give an example of a plant hormone that promotes growth.

► Auxin

4. How do auxins promote the growth of a tendril around a support?


When tendrils come in contact with any support, the part of the tendril in contact with the object does not grow as rapidly as the part of the tendril away from the object. This is caused by the action of auxin hormone. Less auxin occurs on the side of contact as compared to the free side. As a result, auxin promotes growth on the free side and the tendrils coil around the support.

5. What is the role of the brain in reflex action?


The brain has no direct involvement in reflex actions. They are mainly controlled by the spinal cord as these actions do not require thinking and are very quick.

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