Question

(A) How is the movement of leaves of a sensitive plant different from the downward movement of the roots ?
OR
(B) There is a hormone which regulates carbohydrate, protein and fat metabolism in our body. Name the hormone and the gland which secretes it. Why is it important for us to have iodised salt in our diet?

Answer 1

Part (A):
The movement of leaves of a sensitive plant (like Mimosa pudica) is different from the downward movement of the roots in the following ways:

Movement of Leaves in Sensitive Plant:
- The movement of leaves in sensitive plants is known as seismonastic movement, which is a type of rapid response to physical stimuli such as touch or shaking.
- This movement is due to a change in turgor pressure in the cells of the leaflets, causing them to fold or droop when disturbed. The response is rapid and reversible, occurring within a few seconds.
- The movement of leaves is a protective mechanism to deter herbivores or prevent damage from excessive wind or other environmental factors.

Movement of Roots:
- The downward movement of roots is a form of positive geotropism, where the roots grow in the direction of gravity.
- This movement is slow and is regulated by the plant hormone auxin, which promotes the growth of cells on the lower side of the root, causing the root to bend and grow downward.
- Roots move downward to anchor the plant and search for water and nutrients in the soil.

In summary, the leaf movement in sensitive plants is rapid and a response to physical stimuli, while root movement is slow, occurring in response to gravity to support the plant's growth and nutrient absorption.

Part (B):
The hormone that regulates carbohydrate, protein, and fat metabolism in our body is insulin. This hormone is secreted by the pancreas, specifically by the beta cells of the islets of Langerhans.

Importance of Iodised Salt in Our Diet:
Iodised salt is important in our diet because iodine is an essential trace element required for the production of thyroid hormones, thyroxine (T4) and triiodothyronine (T3). These hormones are essential for regulating metabolism, growth, and development in the body.
- Iodine deficiency can lead to thyroid-related problems, such as goitre and hypothyroidism, which can affect physical and mental development, particularly in children.
- Iodised salt helps prevent these conditions and ensures proper thyroid function.