Introduction
Climate change is accelerating the occurrence and intensity of abiotic stresses, including heat, drought, salinity, cold events, and extreme light exposure, creating increasingly unstable growing conditions for horticultural systems worldwide (Shah et al. 2024). While such stresses have been widely investigated in staple food crops, ornamental plants have received comparatively limited scientific attention despite their high economic value, ecological relevance, and cultural contribution to urban greening, aesthetics, and psychological well-being (Karagüzel 2025;Mircea et al., 2024). Unlike yield-focused crops, ornamental species are evaluated based on aesthetic and postharvest attributes—including floral longevity, pigmentation stability, fragrance, morphology, and leaf quality—which are highly sensitive to abiotic damage (Liu 2025;Partap et al. 2023). Even mild environmental fluctuations can reduce commercial value, underscoring the need for innovative, stress-resilient cultivation strategies amid climate uncertainty.
Nitric oxide (NO), a highly conserved gaseous signaling molecule, has emerged as a key regulator of plant responses to adverse environments. Studies in A. thaliana and rice have elucidated major components of NO biosynthesis and signaling, particularly its role in integrating redox homeostasis, hormone crosstalk, and stress-responsive gene expression via mechanisms such as S-nitrosylation and controlled interaction with reactive oxygen species (ROS) (Hussain et al. 2016;Khan, Al Azzawi et al., 2023;Khan et al. 2023;Khan et al. 2023;Niyoifasha et al. 2023;Rahim et al. 2022). These mechanistic foundations offer a valuable framework for interpreting NO responses in species where molecular annotations are limited—such as ornamentals, many of which lack complete genomic or transcriptomic resources.
Translational evidence from diverse ornamental species—including Rosa, Chrysanthemum, Gazania, Lilium, Gerbera, Petunia, Tagetes, Hibiscus, and Zinnia—demonstrates that endogenous and exogenously applied NO improves tolerance to salinity, drought, heat, and oxidative stress while enhancing flowering, delaying senescence, and improving vase life (Abbasi et al. 2020;Aftab et al. 2024;Ahsan et al. 2025;Arun et al. 2016;Gabaldón et al. 2005;Jafari and Daneshvar 2020;Naing et al. 2017;Park et al. 2023;Seyf et al. 2012). These benefits are largely linked to enhanced antioxidant activity, maintenance of cellular osmotic balance, optimized stomatal behavior, and protection of photosynthetic machinery (Al Azzawi et al. 2023;Corpas et al. 2021;Hajihashemi and Jahantigh 2023;Khan et al. 2019).
Despite these advances, several gaps limit the widespread integration of NO-based approaches in ornamental horticulture. Challenges include inconsistent experimental reporting of donor type, concentration, and timing (Arasimowicz‐Jelonek et al. 2011), limited mechanistic work beyond Arabidopsis and a few model ornamentals (Khan et al. 2023;Wills et al. 2015), and the scarcity of long-term or climate-simulated studies that reflect real-world stress combinations typical of future environmental conditions (Mittler et al. 2022;Muhammad et al. 2025). Furthermore, unique ornamentalspecific traits—such as rapid postharvest decline, pigment instability, and high sensitivity to handling— suggest that NO roles may differ from traditional crop-focused stress paradigms.
Given these considerations, this review aims to synthesize mechanistic insights from NO research in Arabidopsis and relate them to emerging findings in ornamental species under climate change–related abiotic stress conditions. By comparing model-based understanding with translational applications in floriculture, we highlight research priorities, practical considerations, and opportunities for integrating NO-based strategies to enhance resilience and maintain ornamental quality under future environmental scenarios.
Climate Change–Related Abiotic Stress Challenges in Ornamental Plants
Climate change is reshaping environmental conditions, exposing ornamental plants to increasingly variable and unpredictable abiotic stress regimes. Unlike staple crops, where yield remains the primary benchmark, ornamentals are highly sensitive to qualitative damage such as leaf scorching, flower deformation, pigment fading, or premature senescence—traits that directly affect aesthetic and market value. Abiotic stress factors often occur in combination rather than isolation, amplifying physiological strain and accelerating postharvest decline. As a result, floricultural production systems, nurseries, and landscape environments require physiological resilience beyond what many cultivated ornamentals currently possess.
Drought, waterlogging, and heat stress are among the most prevalent consequences of climate warming, driven by extended heat waves and reduced rainfall frequency. These conditions disrupt cellular osmotic balance, impair photosynthesis, and accelerate oxidative stress, resulting in delayed or aborted flowering in species such as G. rigens, Phragmites communis, C. morifolium, and Cucumis sativus (Ahsan et al. 2025;Fan et al. 2014;Song et al. 2006;Yang et al. 2011).
Similarly, salinity stress has become increasingly common due to rising sea levels, soil degradation, and reliance on low-quality irrigation water, reducing biomass, chlorophyll stability, and flower size in species such as petunia and carnation (Abbasi et al. 2020;Arun et al. 2016).
Extreme climate-driven stresses—including cold, ozone, and ultraviolet (UV) exposure—pose increasing challenges to ornamental horticulture, particularly for species with low natural tolerance. Cold stress has been shown to severely impair physiological stability in sensitive ornamental species such as Anthurium andraeanum and Cynodon dactylon (Fan et al. 2015;Sun et al. 2023). In parallel, elevated UV-B radiation—now recognized as a growing environmental pressure linked to atmospheric changes—interacts with heat, drought, and salinity to disrupt pigment regulation, leaf anatomy, and oxidative balance across multiple ornamental taxa (Bornman et al. 2019). Atmospheric ozone pollution represents another emerging threat, reducing photosynthesis and accelerating visible leaf injury in ornamentals including Cotinus coggygria, T. erecta, and R. chinensis, with specieslevel variation in physiological tolerance (Liang et al. 2018). Across these diverse stress contexts, NO appears to function as a key regulatory signal mediating antioxidant activity, stress gene regulation, and redox homeostasis in ornamental species undergoing environmental stress (Simontacchi et al. 2015).
To contextualize these climate-linked challenges, Table 1 summarizes key stress types, their environmental drivers, and representative impacts on ornamental species.
NO as a Stress Regulator: Key Mechanisms (Evidence from Model Plants)
NO is a small, highly diffusible gaseous molecule that functions as a central signaling hub in plant stress responses. In model plants, especially A. thaliana, extensive research has elucidated its biosynthesis, interactions with hormonal and redox networks, and downstream regulation of stress-responsive genes, providing a foundational framework for translational research in ornamentals.
NO biosynthesis pathways
NO production in plants occurs through multiple enzymatic and non-enzymatic routes. The nitrate reductase (NR)-dependent pathway reduces nitrate (NO₃⁻) to nitrite (NO₂⁻), which can then be converted to NO under specific cellular conditions, particularly during abiotic stress (Khan et al. 2023). In addition to NR activity, plants exhibit nitric oxide synthase (NOS)-like activities capable of catalyzing NO formation from L-arginine. However, despite functional evidence of such activities, a canonical animal-type NOS gene has not yet been conclusively identified in higher plants, and its molecular identity remains a subject of ongoing debate and investigation within the research community. Non-enzymatic routes also contribute substantially to NO pools, especially under acidic conditions or in the presence of reducing agents, facilitating rapid NO accumulation during oxidative or environmental stress (Khan et al. 2023). Together, these complementary pathways enable plants to fine-tune NO homeostasis and ensure precise spatiotemporal signaling in response to developmental cues and stress stimuli.
Crosstalk with Hormonal Signaling
NO interacts extensively with phytohormones, integrating stress perception with growth and developmental modulation. Abscisic acid (ABA) and NO act synergistically to regulate stomatal closure under drought and heat stress, optimizing water-use efficiency (Lombardo and Lamattina 2018). NO also modulates ethylene biosynthesis and signaling, influencing senescence and programmed cell death, while interacting with jasmonic acid and salicylic acid pathways to orchestrate defense responses (Khan et al. 2021;Khan et al. 2023). This hormonal crosstalk ensures that NO-mediated signaling is dynamically adjusted according to stress intensity, developmental stage, and tissue type.
Regulation of ROS–NO Balance
Abiotic stresses often lead to excessive accumulation of ROS, which can cause oxidative damage. NO contributes to maintaining redox homeostasis through direct scavenging of ROS and by modulating the activity of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX). This fine-tuned balance between ROS and NO not only mitigates cellular damage but also functions as a signaling mechanism, where transient ROS bursts act in concert with NO to activate adaptive responses (Khan et al. 2023;Rahim et al. 2022;Rolly et al. 2020).
Post-Translational Modifications
A key mechanism by which NO exerts its regulatory effects is through post-translational modifications, particularly S-nitrosylation—the reversible addition of a NO group to cysteine thiols on target proteins. S-nitrosylation can alter protein activity, localization, stability, or interactions, enabling rapid modulation of signaling networks in response to environmental cues. In Arabidopsis, proteins involved in photosynthesis, antioxidant defense, hormone signaling, and transcriptional regulation have been identified as NO targets, highlighting the breadth of NO-mediated modulation (Pande et al. 2022).
Regulation of Stress-Responsive Genes and Transcription Factors (TFs)
NO also regulates gene expression by influencing TFs and stress-responsive genes. Key TF families, including WRKY, NAC, and bZIP, are modulated by NO under various abiotic stresses (Aslam et al. 2019;Falak et al. 2021;Nabi et al. 2021). WRKY TFs are often involved in ROS detoxification and defense signaling, NAC TFs coordinate osmotic and heat stress responses, and bZIP TFs regulate ABA-dependent stress pathways (Aslam et al. 2019). Through these targets, NO can orchestrate a broad transcriptional reprogramming, integrating environmental signals with growth and defense priorities.
Translational Relevance for Ornamentals
Collectively, these mechanistic insights from model plants serve as a “toolbox” for ornamental research. By understanding NO biosynthesis, hormone interactions, ROS regulation, post-translational modifications, and gene regulatory networks, researchers can identify candidate pathways and molecular targets to enhance stress tolerance in ornamental species. This framework is particularly valuable for species with limited genomic resources, allowing hypothesis-driven experimentation using exogenous NO donors, priming strategies, or molecular breeding approaches to improve resilience under climate change-related stresses.
Evidence of NO-Mediated Stress Tolerance in Ornamental Plants
Accumulating evidence demonstrates that NO acts as a multifunctional regulator of stress tolerance in ornamental species, functioning through mechanisms that parallel—but are not always identical to—those characterized in model plants. Ornamentals exhibit high sensitivity to environmental fluctuations and rapid postharvest decline, making NO particularly relevant in improving both stress resilience and market value.
NO enhances stress tolerance and physiological performance by regulating antioxidant defense systems, maintaining osmotic and ionic balance, modulating cellular redox signaling, stabilizing proteins via S-nitrosylation, and interacting with hormonal pathways including ABA, ethylene, and jasmonates. Exogenous application of NO donors, such as SNP or S-nitrosoglutathione (GSNO), has been shown to alleviate abiotic stress and delay senescence in multiple ornamental genera, including Rosa, Tagetes, Gazania, Gerbera, Lilium, Chrysanthemum, Petunia, Zinnia. Additionally, NO treatments frequently extend vase life, preserve pigment stability, and maintain overall postharvest quality (Abbasi et al. 2020;Aftab et al. 2024;Ahsan et al. 2025;Arun et al. 2016;Gabaldón et al. 2005;Jafari and Daneshvar 2020;Naing et al. 2017;Park et al. 2023;Seyf et al. 2012).
Drought Stress
Drought remains one of the most limiting factors in ornamental horticulture, affecting both vegetative growth and flowering quality, similar to its impact observed in rice (Al Azzawi et al. 2020). NO enhances drought tolerance by regulating stomatal closure, maintaining water-use efficiency, and activating antioxidant systems to mitigate oxidative stress (Khan et al. 2019). Studies in G. rigens, T. erecta, L. esculentum, Festuca arundinacea, F. glaucescens, and Lagenaria siceraria have shown that exogenous application of NO donors such as sodium nitroprusside (SNP) increases SOD and CAT activities, reduces lipid peroxidation, and stabilizes photosynthetic performance under water-deficit conditions (Kaya et al. 2024;Liao et al. 2012;Perlikowski et al. 2022;Zhang et al. 2024).
Salinity Stress
Soil salinity impairs ornamental growth by disrupting ion balance and increasing oxidative stress. NO mitigates these effects by improving Na⁺/K⁺ homeostasis, strengthening antioxidant defenses, and stabilizing cellular membranes. For example, SNP treatment in G. jamesonii and Hylotelephium erythrostictum increased chlorophyll levels, enhanced antioxidant enzyme activity, and reduced lipid peroxidation (Abbasi et al. 2020;Chen et al. 2019;Wang et al. 2024). Similar physiological improvements observed in Petunia hybrida and other plant systems support a conserved NO-mediated salt tolerance mechanism involving ion regulation, redox control, and gene expression adjustment (Alnusairi et al. 2021;Arun et al. 2016;Wei et al. 2022).
Heat Stress
Heat stress causes protein denaturation, membrane damage, and photosynthetic impairment. NO enhances thermotolerance through antioxidant activation and modulation of heat-responsive transcriptional pathways. In C. morifolium, SNP treatment maintained chlorophyll content, reduced oxidative injury, and elevated SOD, CAT, POD, and APX activities (Yang et al. 2011). Transcriptomic evidence in L. longiflorum further demonstrates NO-mediated induction of HSPs via heat shock transcription factors (HSFs), contributing to cellular protection under elevated temperatures (Zhou et al. 2022). Similar benefits are reported in Arabidopsis, T. aestivum, and S. lycopersicum, where NO enhances PSII efficiency, improves ROS homeostasis, and strengthens heat-responsive gene expression (Hasanuzzaman et al. 2012;Parankusam et al. 2017;Wu et al. 2012;Zhao et al. 2010). Collectively, these findings demonstrate that NO protects photosynthetic machinery, enhances antioxidant defenses, stabilizes membranes, and activates HSF–HSP pathways, positioning it as a promising biostimulant for improving heat tolerance in ornamental and crop species.
Cold Stress
Low temperatures impair membrane function, metabolism, and reproductive development. NO contributes to cold tolerance by reducing oxidative stress, increasing osmolyte accumulation, and activating cold-responsive signaling cascades. Pretreatment with SNP in Anthurium andraeanum reduced electrolyte leakage and enhanced antioxidant responses (Liang et al. 2018). In Ziziphus jujube, NO-mediated S-nitrosylation stabilized antioxidant enzymes during chilling (Zhang et al. 2023).
Mechanistic insights from model plants confirm NO involvement in CBF-dependent cold response pathways (Zhao et al. 2009). reinforcing its role in low-temperature adaptation of ornamentals.
Postharvest Senescence
Postharvest decline is a major bottleneck in the ornamental industry. NO delays floral senescence by suppressing ethylene synthesis, reducing ROS accumulation, and maintaining pigment and membrane integrity. SNP applications have extended vase life and improved postharvest attributes in R. hybrida, Dianthus caryophyllus, Gladiolus, and Consolida ajacis (Liao et al. 2013;Naing et al. 2017;Seyf et al. 2012;Ul Haq et al. 2021;Zulfiqar et al. 2024). Further, NO enhanced pigment retention in Narcissus tazetta and improved solution uptake and oxidative balance in Antirrhinum majus (Farooq et al. 2024;Hajihashemi and Jahantigh, 2023). These outcomes emphasize the potential of NO as a postharvest biostimulant.
Table 2 summarizes representative studies demonstrating the role of exogenous NO in enhancing stress tolerance, improving developmental traits, and extending postharvest longevity in ornamental plants. The table consolidates species, stress categories, NO source and concentrations, major physiological responses, and functional outcomes. By organizing evidence across systems, Table 2 highlights the consistency of NO-mediated regulatory effects and identifies concentration ranges frequently reported as effective across species.
Fig. 1 illustrates the integrative role of NO as a master regulator of plant responses to abiotic stress. NO is generated through multiple interconnected routes, including nitrate reductase (NR)-dependent and NOS-like enzymatic pathways, as well as non-enzymatic, ROS-mediated, and antioxidant-associated processes, reflecting the tight coupling between redox metabolism and NO signaling. Once formed, NO exerts its regulatory function primarily through post-translational modifications, particularly S-nitrosylation, which alters the activity of key regulatory proteins such as TFs and stress-responsive enzymes. Through these molecular modifications, NO fine-tunes stress signaling either by directly targeting cellular components or by acting synergistically with other signaling messengers.
At the physiological level, NO-mediated regulation translates into distinct stress-adaptive functions: under drought conditions, NO promotes stomatal closure and osmotic adjustment; during salinity stress, it contributes to Na⁺/K⁺ homeostasis; under heat stress, it enhances thermotolerance through heat shock protein induction and ROS detoxification; during cold stress, it supports membrane stabilization and antifreeze protein regulation; and in postharvest contexts, NO delays senescence by suppressing ethylene signaling. Collectively, these coordinated molecular and physiological actions underscore NO as a versatile and integrative regulator of plant stress resilience.
Translational Lessons from Model Plants to Ornamentals
Mechanistic insights derived from A. thaliana and other model plants provide a powerful foundation for translating NO-mediated stress tolerance into ornamental plant systems. Core discoveries related to enzymatic and non-enzymatic NO biosynthesis, S-nitrosylation-based protein regulation, ROS–NO signaling integration, and TF–mediated control of stress-responsive genes define a transferable regulatory framework that is highly relevant to ornamentals facing increasing environmental instability. Unlike food crops, ornamental plants must maintain not only survival and productivity but also strict aesthetic standards, including flower size, color, form, and postharvest longevity. Thus, the translation of NO biology into this sector requires precision strategies that enhance stress resilience without compromising visual and commercial quality. As illustrated in Fig. 2, four complementary translational routes emerge that bridge molecular mechanisms with applied ornamental horticulture.
Fig. 2A highlights genome editing as a precise strategy for manipulating NO biosynthesis and signaling pathways in ornamentals. Targeted modification of genes encoding nitrate reductase, NOS-like enzymes, NO-responsive TFs, and redox regulators using CRISPR/Cas technologies enables fine control of endogenous NO production and downstream stress signaling. Such precision editing allows enhancement of drought, salinity, heat, and cold tolerance while preserving floral morphology, pigmentation, and fragrance—traits that are often negatively affected by conventional stress-tolerance breeding. Importantly, this approach also enables the uncoupling of stress resistance from growth penalties, offering a major advantage for high-value ornamental species where both stress performance and aesthetic quality must be optimized simultaneously. In parallel, Fig. 2B emphasizes the exploitation of natural variation through systematic screening of ornamental germplasm for NO responsiveness. By evaluating cultivars, breeding lines, and wild relatives for endogenous NO levels, NO-induced antioxidant capacity, ion homeostasis, and membrane stability, superior NO-responsive genotypes can be identified and directly integrated into breeding or vegetative propagation programs. This strategy is particularly powerful for clonally propagated ornamentals, where elite stress-resilient phenotypes can be rapidly fixed and deployed without lengthy breeding cycles.
Beyond genetic approaches, Fig. 2C illustrates the direct integration of NO into propagation and crop-management practices through the application of exogenous NO donors and NO-priming treatments. Compounds such as SNP and GSNO can be applied during seed germination, seedling establishment, irrigation, and postharvest handling to enhance antioxidant enzyme activity, stabilize cellular membranes, regulate ion balance, and suppress stress-induced senescence. In ornamental production systems, these physiological benefits translate into improved establishment under stress, delayed leaf yellowing, maintenance of pigment intensity, and prolonged vase life of cut flowers. This management-based strategy is especially attractive because it is rapid, cost-effective, and readily scalable for commercial nursery and greenhouse operations without requiring genetic modification.
Finally, Fig. 2D underscores the importance of bridging mechanistic NO research with applied validation under realistic climate stress scenarios. Integrating molecular and physiological NO responses with ornamental-specific performance traits under cyclic drought, heat waves, salinity intrusion, and enhanced UV exposure ensures that laboratory-derived benefits remain stable in real-world production systems. Such integrative testing also allows the identification of potential trade-offs between stress protection and decorative quality, a critical limitation that currently restricts the deployment of stress physiology innovations in ornamental horticulture.
Together, the four translational strategies summarized in Fig. 2 establish a coherent pipeline that moves from NO-regulated genes and signaling networks to elite cultivar development and climate-resilient crop management systems. By aligning molecular precision tools, physiological screening, and industry-ready management practices, NO-centered approaches provide a powerful framework for transforming ornamental stress management from empirical intervention to mechanism-guided innovation. In the context of intensifying climate variability, such integration is essential for safeguarding both the sustainability and the high commercial value of ornamental plant production.
Practical Applications and Future Potential
NO offers multiple practical opportunities to enhance ornamental plant resilience and quality across production phases. Exogenous NO donors such as SNP and GSNO can be applied foliarly or via substrate to improve drought, salinity, heat, and oxidative stress tolerance while maintaining key aesthetic traits such as color uniformity, petal integrity, and vegetative form. Seed priming and nursery-stage NO treatments further enhance germination, early vigor, and stress preparedness, offering particular value for high-cost or stress-sensitive floriculture crops.
In the postharvest phase, NO application delays senescence, inhibits ethylene action, stabilizes pigmentation, and extends vase life in cut flowers including rose and carnation, contributing to reduced waste and improved marketable shelf life. These effects translate into potential economic benefits through decreased postharvest losses and longer retail display periods.
Emerging strategies, including nanotechnology-based NO delivery systems and controlled-release formulations, have shown promise for improving delivery precision, stability, and treatment efficiency. However, adoption of such advanced technologies may be constrained by production costs, regulatory requirements, and scalability challenges. While early studies indicate that long-term returns may offset investment—particularly through reduced chemical inputs and improved postharvest longevity—comprehensive cost–benefit assessments and field-scale evaluations remain needed before widespread commercial deployment.
Future integration with automated irrigation, hydroponics, and smart greenhouse systems could enable real-time, demand-driven NO application, supporting precision horticulture tailored to climate-adaptive production. Collectively, these applications position NO as a versatile tool capable of bridging mechanistic understanding with scalable, economically informed solutions for ornamental horticulture.
Conclusion
NO represents a central regulator of plant stress tolerance with considerable potential for ornamental horticulture under climate change. Insights from model plants such as A. thaliana have revealed key biosynthesis pathways, hormonal interactions, redox regulation, and transcriptional networks that can be directly translated to ornamentals. Evidence from numerous plants demonstrates that NO enhances drought, salinity, heat, cold, and postharvest stress tolerance, largely through antioxidant activation, osmotic regulation, and hormonal modulation.
Practical applications—ranging from exogenous NO donors, seed priming, and postharvest treatments to advanced nanotechnology-based delivery and integration with smart greenhouse systems—highlight NO’s potential as a climate-resilience tool for floriculture. Future research should focus on translating mechanistic insights from model species, optimizing application protocols, and screening ornamental germplasm for NO responsiveness. By bridging fundamental biology with applied horticulture, NO-based strategies can enhance ornamental plant quality, longevity, and sustainability in an era of increasingly variable and extreme environmental conditions.
