system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When plants face the sun, how do they know where the sun is, and how are they able to orient themselves?
gpt
There are cells in the stem of the plant that grow at different rates depending on if they are lit by the sun or not. The ones that are not in sunlight grow more than the ones that are, causing the stem of the plant to twist towards the sun. When you watch a time lapse of a plant growing it can really look like the plant “knows” where the sun is, and is actively moving towards it, but in reality the directional growth is just caused by chemical reactions, and is completely automatic.