Shade avoidance

From Freepedia

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, because of the altered balance between red and far-red light in the shade of a plant. This balance between red and far-red light is perceived by phytochrome.