Chapter 24: Abiotic Stress in Plants

Rather than representing simple deterioration, senescence functions as a highly regulated developmental program controlled by complex molecular mechanisms and hormonal networks. The chapter explores how key plant hormones including ethylene, abscisic acid, jasmonic acid, and salicylic acid coordinate senescence initiation and progression, while cytokinins act as natural senescence inhibitors that prolong tissue viability. Environmental factors such as drought stress, nutrient depletion, pathogen attack, and light availability serve as critical triggers that modulate senescence timing through intricate signaling pathways. The molecular basis of senescence involves senescence-associated genes, specialized transcription factors, reactive oxygen species signaling cascades, and autophagy mechanisms that systematically dismantle cellular components for nutrient recycling. Specific examples of programmed cell death include tracheary element differentiation during xylem formation and aerenchyma development in response to hypoxic conditions, illustrating how controlled cell death supports plant survival strategies. The chapter demonstrates how nutrient remobilization during senescence allows plants to salvage valuable resources from aging tissues and redistribute them to developing organs or storage sites. Hormonal crosstalk mechanisms coordinate these processes, ensuring that senescence occurs at optimal times for plant fitness. The discussion extends to practical agricultural applications, exploring genetic and hormonal approaches to manipulate senescence timing for improved crop yield and postharvest preservation, highlighting the economic importance of understanding these fundamental biological processes.