Shade Avoidance Syndrome: A Colour Ratio Regulated Growth

Abstract

When plants are exposed to the shade of another plant, they exhibit a set of responses called shade avoidance syndrome (SAS). The most remarkable trait observed in plants subjected to low R:FR are an upward reorientation of leaves (leaf hyponasty) and a rapid elongation of leaves and stems. PIF (Phytochrome Interacting Factor) and DELLA gene families interact with endogenous and external signals, which are mediated by several photoreceptors including phytochrome, cryptochrome, and UVR8, and are the main regulators of molecular responses for shade signalling. Plants combine information about R: FR with a variety of signalling routes, which involve environmental elements and plant hormones such as auxin, gibberellin, ethylene, and brassinosteroid. In order to balance resource allocation between development and defence, shade also represses defence responses caused by salicylic acid and jasmonate. These molecular discoveries aidto understand the mechanisms of plant strategies such as dampening of shade-avoidance traits and optimizing growth under low light conditions to foster crop improvement and also to develop shade tolerant varieties for different agricultural ecosystems.