Phototropism

plants · light · growth · biology

Plants chase light. When a plant senses light, it grows toward it in a movement called positive phototropism. This helps the plant capture more sunlight for energy and growth.

Auxin makes it happen. A plant hormone called auxin gathers on the shaded side of a stem, making those cells grow longer. This causes the whole plant to bend and lean toward the light source.

Some grow away. Certain vines actually grow away from light or toward darkness, called negative phototropism. This helps them find dark spaces and climb up trees and walls.

Leaves rearrange too. Plants don't just bend, they also shuffle their chloroplasts (the parts that catch light) around inside their leaves to grab the maximum sunlight possible.

Works with gravity. Phototropism teams up with gravitropism (how plants respond to gravity) so plants grow the right way: stems up toward light and roots down into soil.