How does plant respond to sunlight ?

Explanation

1) Auxins are phytohormones which are responsible for bending of plants in response to light. This is called phototropism.
2) Charles Darwin and his son Francis Darwin performed some experiments on phototropism and stated that when seedlings are freely exposed to lateral light some 'influence' is transmitted from upper to the lower part causing the plant to bend.
3) This is the chemical stimulus known as auxin, which helps the plant growing towards light.
4) The phototropism occurs in plants by the plant hormone auxin acts on bending of stem to show response to the stimulus (sunlight).