(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.
(a) Phototropism is the growth of plant parts in response to a light stimulus. During phototropism, the cells on the plant that are farthest from the light contain a chemical called auxin reacts, which causes the plant to have elongated cells on the furthest side from the light. Hence, shows the growth and movement toward light.
An example of phototropism is the growth of plant stem in the direction of sunlight (upward).
(b) In a plant, stem (or shoot) shows positive phototropism, as it grows towards the sunlight.
(c) The movement or growth of plant parts towards the light source is known as positive phototropism, whereas the movement or growth of plant parts away from light is known as negative phototropism.
Example- Positive Phototropism - Stems (grow upwards), Negative Phototropism - Roots (grow downwards).
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