Phototropism is the growth response of a plant to light. Shoots are usually positively phototropic, meaning they grow towards the light to maximise the amount of light they receive for photosynthesis. The tip of the shoot detects the direction of the light and produces a plant hormone called auxin. Auxin moves to the shaded side of the shoot, causing those cells to elongate more, which makes the shoot bend towards the light. Roots are usually negatively phototropic, meaning they grow away from light. Phototropism is an important example of how plants respond to environmental stimuli and is a key topic in GCSE Biology.
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