Shade Avoidance Responses. Driving Auxin along Lateral Routes

Abstract

To grow and develop optimally, all organisms need to perceive and process information from their environment. As sessile organisms, plants need to sense and respond to external stimuli more than most organisms. Therefore, plants have to adapt their developmental pattern to the environmental changes to ensure survival and reproduction. As a consequence, numerous environmental factors, including temperature, touch, water, gravity, and light, can exert a profound influence on the form assumed by individual plants, affecting overall plant size and the number and size of individual organs. Cues from the light environment are involved in the regulation of seed germination, the establishment of seedlings, the determination of growth habit, and the transition to flowering. To perceive information about their light environment, plants have evolved at least three families of photoreceptors that specifically recognize different wavelengths of light: the red (R)/far-red (FR)-sensing phytochrome family, the blue/UV-A photoreceptors called cryptochromes, and the UV-B photoreceptors (Kendrick and Kronenberg, 1994).