Eustress and hormesis improve quality resilience and resource efficiency in horticultural crops through controlled preharvest stress management

Horticultural production has traditionally prioritised yield, often at the expense of nutritional quality and health-promoting phytochemicals. This review synthesises the conceptual basis and preharvest operationalisation of eustress and hormesis in horticultural crops, distinguishing eustress as a deliberately managed, mild, non-injurious stress input from hormesis as the underlying biphasic dose–response principle, and positioning priming as a time-dependent stress-memory phenomenon where relevant. Mechanistically, mild abiotic stimuli can maintain reactive oxygen species (ROS) within signalling-competent ranges, engage antioxidant networks, and modulate flux through phenylpropanoid and carotenoid pathways. Across crops, such interventions can enhance selected bioactive compounds in edible tissues (e.g., phenolics/anthocyanins and carotenoids), but outcomes depend on dose, exposure duration, phenological stage, genotype, and environment, with narrow margins before distress and growth/yield trade-offs occur. Representative cases include regulated deficit irrigation in grapevine and moderate salinity management in tomato, where phenylpropanoid- and carotenoid-linked quality traits have been reported to shift within cultivar- and stage-specific hormetic windows. Crop-based evidence is synthesised for preharvest strategies including regulated deficit irrigation, controlled salinity, thermal priming, and exogenous elicitor applications, with emphasis on dose–time–phenology alignment and monitoring. Distinct from prior general treatments, this review focuses specifically on horticulture-oriented, preharvest eustress protocols and provides a decision-relevant framing to translate hormetic windows into operational practice within precision management and sustainability constraints.