Plant Adaptation in a Changing Climate: From Molecular Mechanisms to Ecosystem Resilience

Plants increasingly experience recurrent heat, drought, cold anomalies and compound stresses whose timing and intensity differ from the historical environments in which many crops and wild populations evolved. Stress memory describes persistent molecular or physiological states produced by an initial exposure that modify later responses, but the term is often used too broadly and can obscure major differences between transient acclimation, mitotically maintained transcriptional memory, parental effects and true transgenerational inheritance. This critical narrative review evaluates evidence for epigenetic, chromatin and cross-generational mechanisms of plant stress memory, with emphasis on their causal support and relevance to climate adaptation. Literature published from 1 January 2000 to 15 July 2026 was examined, alongside conceptually essential foundational studies, using multidisciplinary scholarly sources and citation tracing. The strongest mechanistic evidence concerns somatic heat memory in Arabidopsis thaliana, where heat-shock transcription factors, sustained H3K4 methylation, chromatin remodelling, transcriptional machinery, small RNAs and protein turnover form interacting memory modules. Recurrent dehydration also produces reproducible transcriptional memory, yet genome-wide studies show that DNA methylation inheritance is neither universal nor necessary for all drought-memory phenotypes. Cross-generational evidence is more heterogeneous because reproductive reprogramming, maternal provisioning, genotype, selection and experimental design can mimic epigenetic inheritance. Particularly informative recent work in rice demonstrates a causally validated, stably inherited DNA-methylation state at ACT1 that contributes to acquired cold tolerance, whereas studies in clonal strawberry and duckweed indicate that asexual propagation can permit broader persistence of environmentally induced methylation states. The field therefore supports a hierarchy of evidence rather than a single model of memory. Future progress depends on locus-specific causal perturbation, stress-free intervening generations, reciprocal reproductive designs, climate-realistic compound exposures and multi-site fitness or yield validation. Stress memory is best viewed as a conditional component of plant adaptive plasticity whose value depends on persistence, reversibility and environmental predictability.