Shade avoidance

From Wikipedia, the free encyclopedia

Shade avoidance is a set of responses that plants display when they are subjected to the shade of another plant. It often includes elongation, altered flowering time, increased apical dominance and altered partitioning of resources. This set of responses is collectively called the shade-avoidance syndrome.

Plants can tell the difference between the shade of an inanimate object (eg a rock) and the shade of another plant. In the shade of a plant, far red light is present in a higher irradiance than red light, as a result of the absorption of the red light by the pigments involved in photosynthesis. Phytochrome can be used to measure the ratio of far-red to red light, and thus to detect whether the plant is in the shade of another plant, so it can alter its growth strategy accordingly (photomorphogenesis). The shade avoidance response is also used by some seeds to detect if there is a break in the canopy, in order to germinate at the most advantageous time for successful growth.