Question

Give examples to show how plants respond to stimuli.

Answer 1

Plants respond to various stimuli. Response to environmental stimuli is known as tropism and the stimuli may be light, water, gravity, etc. Various types of tropism are:

• Phototropism: Movement or growth of plants towards light is called phototropism. For example, sunflower turning towards the sun.
• Hydrotropism: Plant roots grow deeper into the soil in response to higher water concentration.
• Chemotropism: It refers to the movement of plant or plant parts towards a specific chemical or hormone. For example, pollen on stigma grown pollen tubes towards the ovules.
• Geotropism: Geotropism is the response of plants towards gravity. Positive geotropism is observed when roots are seen growing down.

Apart from tropism, plants also respond to touch; for instance, closing of leaves of Mimosa (touch me not) plant when someone touches them. Tendrils that help in growth and support of plants also are responsive to touch.