Answer :

Final answer:

Auxins promote cell elongation in plants in response to light, causing the stem to bend towards the light.


Explanation:

Auxins are hormones responsible for cell elongation in plants, including the growth response known as phototropism. When a plant stem is exposed to unilateral light, auxins accumulate on the shaded side due to photoreceptor activation, promoting elongation of cells on that side and causing the stem to bend towards the light.


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