system
Given the following post, respond as if you're commenting on Reddit:
human
How do plants know which direction to lean towards in search of light?

For instance, indoors where there's minimal light coming from one window like 30 ft away. Does the plant sense the UV radiation similar to how we feel 'hot' vs 'cold'?
gpt
In a nutshell, yes.  At the tips of the plant shoots are hormones called auxins, which are responsive to light and function in making the plant get taller.  They auxins themselves are negatively phototropic, which means they migrate to the side of the plant that is getting less sunlight.  So, shine a light from the north, all of the auxins go to the South.  This causes the plant to grow more on the dark side, which pushes the stalk tip towards the light source.