Tolerance and Response of Ornamental Plants to Abiotic Stress

1. Introduction

Ornamental plants play a pivotal role in environmental decoration, ecological balance, and air purification. However, they are facing escalating challenges from abiotic stresses, including heavy metal pollution, extreme temperatures, drought, salinity, and ozone exposure [1]. These stresses disrupt plant growth, metabolism, and survival, necessitating urgent research to unravel the tolerance mechanisms of plants and develop stress mitigation strategies. This Special Issue, “Tolerance and Response of Ornamental Plants to Abiotic Stress,” compiles cutting-edge studies exploring how ornamental species adapt to diverse abiotic pressures, offering insights into their physiological, biochemical, and molecular responses. Through a rigorous peer review process, 10 research articles were selected, spanning topics ranging from stress physiology to innovative mitigation techniques, which collectively advance our understanding of ornamental plant resilience.

2. Overview of Published Articles

The articles in this Issue address various abiotic stressors and tolerance mechanisms associated with multiple ornamental species. They are categorized into four thematic areas:

2.1. Physiological and Biochemical Adaptations to Stress

The studies in this category focus on how plants modulate physiological processes in order to cope with stress. For example, Kryuchkova et al. (2025) investigated winter hardiness in Lavandula angustifolia hybrids, identifying critical climatic factors (e.g., temperature fluctuations and snow cover) influencing their survival. The study revealed that hybrids with stable antioxidant enzyme activity exhibited superior cold tolerance, providing a foundation for breeding cold-resistant cultivars [2]. Wang et al. (2023) evaluated pH stress tolerance in Rhododendron genotypes through a 140-day greenhouse experiment, demonstrating that a neutral pH (6.3) significantly inhibited root development, plant height, and biomass accumulation, while causing chlorosis and reducing chlorophyll fluorescence (Fv/Fm). Notably, the genotype PB-T3-4 showed superior tolerance, maintaining root growth and photosynthetic efficiency under a neutral pH, highlighting how genetic variation can influence stress adaptation [3]. Shala et al. (2024) explored the role of gamma-aminobutyric acid (GABA) in alleviating the effects of salinity stress in Lavandula dentata. Foliar application of 40 mM GABA mitigated chlorophyll degradation, enhanced the accumulation of osmolytes (e.g., proline), and improved antioxidant enzyme activity, demonstrating its potential as a cost-effective stress mitigator [4].

2.2. Chemical and Molecular Interventions

Several studies highlight the efficacy of chemical compounds and gene regulation in enhancing stress tolerance. Liu et al. (2025) demonstrated that hydrogen sulfide (H₂S) alleviates manganese toxicity in Malus hupehensis by regulating the ascorbate–glutathione cycle and mineral homeostasis. H₂S treatment reduced Mn accumulation in the roots and upregulated the activity of metal transporters (MTPs), emphasizing its dual role in detoxification and nutrient balance [5]. Elmongy and Abd El-Baset (2024) investigated melatonin’s effects on heat-stressed carnations (Dianthus caryophyllus). Melatonin at a concentration of 5–10 mM enhanced the carnations’ chlorophyll content, reduced the abundance of reactive oxygen species (ROS), and upregulated heat shock proteins (HSP70, HSP101), showcasing its potential to improve thermal resilience in ornamental crops [6].

2.3. Molecular and Genetic Mechanisms

Genomic and transcriptomic analyses dominate this theme. Yu et al. (2024) characterized the Isopentenyl Diphosphate Isomerase (IPI) gene in Fritillaria unibracteata, revealing its role in β-carotene synthesis and drought/salt tolerance. Transgenic Arabidopsis plants that overexpressed FuIPI exhibited higher abscisic acid levels and stress resistance, highlighting the utility of this gene for the genetic improvement of liliaceous plants [7]. Li et al. (contribution 5) used transcriptomics to dissect the effects of light and temperature on Hydrangea macrophylla. Key genes involved in photosynthesis (e.g., PHYB, PSBR) and hormone signaling (e.g., PIN3, EIN3) were identified, providing molecular markers for breeding shade-tolerant hydrangea cultivars [8].

2.4. Non-Destructive Monitoring and Stress Assessment

Innovative technologies for stress detection are showcased in two studies. Dmitriev et al. (2024) developed a hyperspectral imaging model to distinguish “Vegetation” and “Dormancy” states in conifers (Platycladus orientalis, Thuja occidentalis). Using linear discriminant analysis (LDA) and random forest algorithms, the model achieved >92% accuracy in the diagnosis of conifers’ phenological states, enabling timely management of conifer plantations under climate change [9]. Qu et al. (contribution 4) proposed a comprehensive method to evaluate cold tolerance in Stenotaphrum accessions by integrating fall dormancy and spring green-up phenotypes. This approach outperformed traditional laboratory assays (e.g., LT50), identifying superior cold-tolerant genotypes (e.g., ST003, S13) for temperate regions [10].

3. Conclusions

The studies presented in this Special Issue collectively advance our understanding of ornamental plants’ responses to abiotic stress, from physiological adaptations to molecular mechanisms. They highlight the potential of chemical priming (e.g., H₂S, GABA), genetic engineering, and non-destructive monitoring techniques to enhance stress resilience. These findings not only provide theoretical insights, but also offer practical tools that can be used by breeders and horticulturists to develop climate-smart ornamental varieties.

We extend our gratitude to all of the authors who made valuable contributions and to the reviewers who conducted rigorous evaluations. We hope that this issue will foster cross-disciplinary collaboration and inspire further research aiming to safeguard ornamental plant sustainability in an increasingly stressful environment.