Question

Explain the role of auxins in the following:

1- phototropism for both root and stem

2- hydrotropism for root

Answer 1

1) Auxins are one of the plant hormone. They are mostly made in the tips of stem and roots. Auxins promotes cell elongation,inhibits the growth of lateral buds. Auxins control the plant growth by promoting cell division and causing elongation in plant cells.

Phototropism is a response to the stimulus of light. In stem, the shaded side contains more Auxins and grows longer. As a result the stem grows towards the light. It grows, because the Auxins causes the cells to elongated on the shaded side. So that side grows more. This unequal growth of two sides causes the growth of the stem towards the light.

Auxins plays opposite effect in roots. In roots the shaded side contains more Auxins and that grows less. That is why root is to bend away from light.

2)Auxins plays key role in bending the plants root towards the water. Because auxin cause the one side growth of root to grow faster than the other and thus the bending of the root. This process is called hydrotropism in plants. The role of Auxins in hydrotropism is vary depending on the plant species.