Abscisic acid and salicylic acid mediated defense: A biochemical review in agroecosystems

Abstract

Plants in agroecosystems are continually exposed to a multitude of abiotic and biotic stresses that threaten their growth, productivity, and survival. To counter these challenges, plants have evolved intricate hormonal signaling networks, with Abscisic Acid (ABA) and Salicylic Acid (SA) emerging as central regulators of stress responses. ABA predominantly governs abiotic stress responses such as drought, salinity, and cold by modulating stomatal behavior, antioxidant defenses, and osmoprotectant accumulation. In contrast, SA orchestrates biotic stress resistance through the activation of systemic acquired resistance (SAR), hypersensitive response (HR), and expression of pathogenesis-related (PR) proteins. However, the relationship between ABA and SA is often antagonistic, particularly under simultaneous stress conditions, where plants must prioritize one signaling pathway over the other. This review comprehensively examines the biosynthesis, signaling pathways, enzymatic responses, and cross-regulatory mechanisms of ABA and SA. It further explores their molecular crosstalk, omics-based insights, field-level applications, crop-specific responses, and biochemical preparation protocols. Emphasis is placed on recent advances in gene expression analysis, enzyme assays, hormone quantification, and integrated stress management strategies. Through crop-wise case studies and practical insights, the paper highlights how a balanced understanding of ABA-SA interactions can inform breeding, biostimulant development, and precision agriculture. Ultimately, this review provides a holistic biochemical framework for leveraging phytohormonal defense to enhance crop resilience and sustainability in a changing climate.