Definition - What does Phototropism mean?

Phototropism refers to the movement of a plant toward a light source. In nature, plants change orientation to face the sun. In an indoor gardening scenario, plants grow toward the light source provided by the gardener.

Essentially, phototropism is a chemical signal; when certain hormones are released in the plant’s system, it responds by growing cells faster on the side facing the light. If you have ever witnessed a plant grown in a pot indoors start to turn toward a nearby window with lots of natural sunlight, you’ve seen phototropism in action.

MaximumYield explains Phototropism

Plants require light in order to manufacture carbohydrates to support growth and life. In the natural world, the light source (the sun) moves across the sky, which changes how light reaches plants. In order to ensure better light absorption, plants have developed a means to change their orientation in relation to a light source. This is called phototropism.

The opposite of phototropism is negative phototropism. Not all parts of a plant need light – the roots actually grow away from light sources. Some plants also grow away from light sources. These are usually those that thrive in shady areas or low light situations.

Other light-related plant movements include photonasty. This process is controlled by the plant, in response to light or its absence. An excellent example of this is a plant opening and closing leaves or flowers at dusk, when light levels drop, or in the morning, when light levels outdoors increase.

In an indoor gardening situation where the light source does not change directions, plants will grow straight up. This may require modification to ensure that the maximum number of plants can be grown within a given area. For example, horizontal gardening requires the training of a plant to grow laterally through a lattice or by being tied down at various points (see Screen of Green Method, or SCROG).

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