PHOTOTROPISM

A plant's movement, or growth, towards or away from something is called a tropism. Growing towards something is positive tropism, while growing away from something is called negative tropism. Plants grow toward light. This is called positive phototropism.

The African Violet pictured to the left grew in low light, so the petioles (leaf stems) lengthened to move the leaves toward the light. Then it was moved into a window. The plant grew towards the window, which is to the right in this photo. It displayed positive phototropism.

When we grow plants for show, we want our plants to grow as evenly as possible, so we try to control phototropism. If we use artificial lights, we try to put them directly over our show plants. If we can't do this, we rotate our plants so they grow evenly on all sides.