Here is information about tropism and phototropism from our Children’s Education Department:

Maybe you have heard that plants can respond to light, touch or gravity. These responses by plants are called “tropisms” and they are a plant’s directed growth to something in the environment. There are several types, but the most common one that people know is phototropism, or a response to grow toward light.

Phototropism--growing or bending in response to light--may be observed in stems that bend toward the light, leaves that orient their flat surfaces towards the light, or even flower heads that face the sun all day. The plant uses this tropism to increase the amount of photosynthesis or to grow toward an area that has more light. A few plants, such as some desert plants with leaves, are negatively phototropic, which means they grow to avoid bright light.

What would happen if you grew a hanging plant in a closet with a bright light underneath?

More about tropism:

Gravitropism: growing or bending in response to gravity
Gravity: force drawing objects to the center of Earth.
Hydrotropism: growing or bending in response to water (Although theoretically possible, there is little evidence that plants exhibit hydrotropism.)
Thigmotropism: growing or bending in response to touch
Tropism: a unique characteristic of plants that enable them to adapt to different features of their environment—gravity, light, water, and touch—so that they can flourish
Photoperiodism: the response of an organism to naturally occurring changes in light during a 24-hour period

For tips on a variety of gardening topics, see our Plant Information Guides.
- Courtesy of NYBG Plant Information Service