Nitric Oxide-Based Signaling During Abiotic Stress Responses in Plants: Mechanisms of Tolerance and Applicability in Sustainable Horticultural Crop Management.

Abiotic stresses severely constrain the growth, yield, and quality of horticultural plants, collectively posing major challenges to sustainable production under changing climatic conditions. Nitric oxide (NO) is a key signaling molecule that modulates plant responses to abiotic stress by integrating with redox regulation systems, hormonal crosstalk pathways, ion homeostasis mechanisms, and transcriptional control networks. Rather than functioning as an isolated regulator, NO participates in dynamic signaling frameworks whose outcomes depend on concentration, timing, cellular redox status, and interaction with other signaling molecules. This review synthesizes current knowledge on NO-mediated mechanisms contributing to abiotic stress tolerance and examines their relevance to sustainable horticultural crop management. After outlining the historical recognition of NO as a plant signaling molecule, we discuss stress-responsive NO-dependent processes, including S-nitrosylation-based post-translational modification, NO-reactive oxygen species (ROS) interactions, and the modulation of stress-responsive transcriptional programs. The roles of NO in tolerance to drought, salinity, extreme temperature, and heavy metal stress are analyzed with emphasis on experimentally supported physiological and molecular responses. We further evaluate evidence from fruit, vegetable, ornamental, and medicinal crops, highlighting how NO-associated signaling correlates with yield stability, quality-related traits, and post-harvest performance under stress conditions. Finally, NO-based strategies such as priming, donor application, and integration with biostimulants are critically assessed in the context of climate-resilient and sustainable horticulture, with attention to translational constraints and field-level feasibility. By connecting mechanistic insights with applied considerations, this review provides a structured framework for evaluating the potential and limitations of NO-based approaches in abiotic stress management of horticultural crops.