Question

(a) Define phototropism. Give one example of phototropism.
(b) How does phototropism occur in a plant stem (or shoot)? Explain with the help of labelled diagrams.
(c) What is meant by positive phototropism and negative phototropism? Give one example of each type.

Answer 1

(a) The growth of plant parts in response to light is known as phototropism. An example of phototropism is the growth of plant stem in the upward direction in response to sunlight.

(b) The stems of plants grow towards sunlight showing positive phototropism.



(c) The movement of plant parts towards the light source is known as positive phototropism, whereas the movement of plant parts away from light is known as negative phototropism.
The stems of plants show positive phototropism as they grow upwards. The roots of plants show negative phototropism as they grow downwards into the soil.