NCERT Class X Science Solutions: Chapter 7 – Control and Coordination Part 2

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Question 6:

How does phototropism occur in plants?


The movement of plant in response to light is called phototropism. Stem shows positive phototropism as follows: When growing plants detect light, a hormone called auxin, synthesized at the shoot tip, helps the cells to grow longer. When light is coming from one side of the plant, auxin diffuses towards the shady side of the shoot. This concentration of auxin stimulates the cells to grow longer on the side of the shoot which is away from light. Thus, the plant appears to bend towards light.

This diagram shows phtotropism occur in plants

Phototropism Occur in Plants

Question 7:

Which signals will get disrupted in case of a spinal cord injury?


The reflex arc connections between the input and output nerves meet in a bundle in the spinal cord. In fact, nerves from all over the body meet in a bundle in the spinal cord on their way to the brain. In case of any injury to the spinal cord, the signals coming from the nerves as well as the signals coming to the receptors will be disrupted.

Result for spinal cord injury.

Spinal Cord Injury

Question 8:

How does chemical coordination occur in plants?


Animals have a nervous system for controlling and coordinating the activities of the body. But plants have neither a nervous system nor muscles. Plants respond to stimuli by showing movements. The growth, development, and responses to the environment in plants is controlled and coordinated by a special class of chemical substances known as hormones. These hormones are produced in one part of the plant body and are translocate to other needy parts. For example, a hormone produced in roots is translocate to other parts when required. The five major types of phytohormone are auxins, gibberellins, cytokinins, abscisic acid, and ethylene. These phytohormones are either growth promoters (such as auxins, gibberellins, cytokinins, and ethylene) or growth inhibitors such as abscisic acid.

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