Plant Stress Memory and Priming: Mechanisms of Acquired Resilience

Plants can retain the physiological and molecular effects of prior stress exposure, thereby modulating their responses to subsequent environmental challenges. Stress priming can lead to a state of modified responsiveness, whereas stress memory refers to the persistence of stress-associated effects that influence subsequent responses. These phenomena have a molecular basis involving interconnected processes at the levels of transcription, epigenetic modifications, hormones, ribonucleic acid (RNA) and metabolism. This study reviews the contributions of transcription factors, chromatin modifications, DNA methylation, small RNAs, phytohormone signalling, reactive oxygen species and metabolic modifications to the formation and expression of plant stress memory. Particular attention is paid to the persistence of stress-related changes, the distinction between molecular correlations and causal mechanisms, and the evidence required to distinguish between intragenerational memory, intergenerational effects and transgenerational inheritance. The review also considers the agricultural importance of seed priming, clonal methods for crop improvement.