Somatic drought stress memory affects leaf morpho-physiological traits of plants via epigenetic mechanisms and phytohormonal signalling

Drought stress memory in plants is an adaptive mechanism that enhances resilience to future water stress through physiological and molecular modifications triggered by previous drought events. This review explores somatic drought stress memory within a plant's lifespan, with a specific focus on leaf and stomatal morphology, minimum leaf conductance, photosynthetic efficiency, water-use efficiency, antioxidant capacity, and leaf senescence. We examine how epigenetic mechanisms—such as DNA methylation, histone modifications, and non-coding RNAs—regulate gene expression in coordination with hormonal signalling pathways. Phytohormones, including abscisic acid, jasmonic acid, ethylene, salicylic acid, auxins and cytokinins, are central to these processes, influencing key morphological and physiological adaptations, such as stomatal regulation, cuticle thickness, water retention, and improved water-use efficiency. The review synthesizes current knowledge on the molecular and hormonal networks underlying these adaptations and their impact on leaf architecture and metabolism. Despite advancements, critical gaps remain in identifying the specific genes and pathways involved, understanding the longevity of epigenetic marks, and elucidating the intricate cross-talk between phytohormones during drought stress memory. This review emphasizes the need for integrated -omics approaches to map epigenetic modifications and uncover their roles in developing drought-resistant plants through targeted stress priming strategies.