phototropism

/ foʊˈtɑtrəˌpɪzəm/

In biology, phototropism is the tendency of plants to move in response to a source of light. If you've ever planted a sunflower and watched it gradually turn to face the sun, you've seen phototropism in action!

Phototropism describes any type of motion that organisms make in response to light, whether they seem to stretch and reach toward it, like sunflowers and other plants, or curl back away from it, like some vines tend to do. Phototropism combines the Greek photo, or "light," and tropism, "tendency of an animal or plant to move in response to a stimulus," from the Greek tropos, "a turning."

Definitions of phototropism

1. noun

   an orienting response to light
   type of:

   tropism

   an involuntary orienting response; positive or negative reaction to a stimulus source