Here's how it works:

* Auxin: Plants produce a hormone called auxin. Auxin accumulates on the shaded side of a plant stem.

* Cell Growth: Auxin stimulates cell elongation on the shaded side. This causes the stem to bend towards the light source, as the cells on the shaded side grow faster than those on the sunny side.

* Light Detection: Plants have special light-sensitive receptors called phototropins that detect blue light, which is most effective for triggering phototropism.

This bending towards the sun is crucial for plant survival because:

* Maximizes Photosynthesis: By positioning their leaves towards the sun, plants maximize their ability to absorb sunlight for photosynthesis, the process that converts light energy into food.

* Access to Nutrients: Sunlight can also affect the distribution of nutrients within a plant, and bending towards the sun helps plants access these nutrients more effectively.

So, next time you see a plant leaning towards the sun, you'll know it's simply doing what it needs to do to thrive!