Phytochrome-mediated shade-avoidance responses and its impact on growth and physiology in crops-A review

Shade stress is a critical environmental constraint that significantly affects plant growth, development, and productivity. Phytochromes, as red and far-red light photoreceptors, play a central role in perceiving shading signals and orchestrating complex physiological and molecular responses in crops. This review provides an analysis of phytochrome-mediated shade stress, highlighting its impacts on key plant processes such as photosynthesis, hormonal regulation, gene expression, and biomass accumulation. We discuss the roles of red and far-red light in modulating phytochrome activity and downstream signaling pathways, emphasizing how these photoreceptors interact with hormonal networks to influence plant morphology, flowering, and stress adaptation. The phytochrome signaling cascade involves intricate light perception and gene regulatory mechanisms that enable plants to adjust their growth under low-light conditions. Differential responses of C₃ and C₄ plants to shade stress are also examined, revealing species-specific strategies for coping with reduced light intensity. Moreover, the review outlines current approaches for managing shading stress, including agronomic practices, genetic interventions, and molecular breeding strategies aimed at enhancing light-use efficiency. By synthesizing recent findings, this article provides insights into the functional roles of phytochromes in mediating shade avoidance and tolerance, offering a framework for future research on crop adaptation to heterogeneous light environments. Understanding phytochrome-mediated mechanisms is crucial for developing resilient cropping systems that maintain productivity under suboptimal light conditions.