Plant defence priming and memory mechanisms under climate change.

Climate change exposes plants to increasingly variable and overlapping abiotic and biotic stresses, challenging ecosystem stability as well as the survival and productivity of crops beyond the limits of classical defence strategies. Defence priming, defined as the capacity of plants to respond faster, stronger, or more effectively following prior exposure, has emerged as a key adaptive mechanism and a promising strategy to enhance plant protection and ecosystem resilience under recurrent or combined stress conditions. Here, current understanding of priming and defence memory in the context of climate change is synthesised, focusing on four interrelated dimensions: (1) the signalling networks that encode and transmit priming, (2) epigenetic and transcriptional mechanisms underpinning somatic and transgenerational memory, (3) physiological and fitness trade-offs associated with primed states under altered temperature, drought, and elevated CO2, and (4) experimental evidence demonstrating how climate-related abiotic factors modulate priming outcomes and plant-pathogen interactions across spatial and temporal scales. Recent studies reveal that climate drivers can both enhance and constrain priming, depending on stress combinations, timing, and intensity. Understanding the mechanisms that determine these context-dependent outcomes will be critical for predicting when priming can be effectively deployed to enhance crop resilience, sustain productivity, and reduce reliance on conventional pesticides under ongoing climate change.