Mitigation of salinity stress in carnation plants through zinc oxide nanoparticles: growth, physiological, and biochemical responses

Carnation (Dianthus caryophyllus L.) growth and floral yield are severely reduced when grown in soils with excessive salinity. Mitigation of adverse effects from salinity-induced stress is necessary for sustainable carnation cultivation. Although various approaches have been developed, the use of zinc oxide nanoparticles (ZnO-NPs) to ameliorate these effects remains scarcely explored. The current study explored the potential of ZnO-NPs to alleviate salinity-induced stress by examining their effects on morphophysiological and biochemical traits. A controlled pot experiment was conducted using a factorial design with three concentrations of sodium chloride (0, 50, and 100 mM) and three of ZnO-NPs (0, 50, and 100 mg L^–1). Elevated salinity significantly impaired plant height, root development, leaf production, chlorophyll content, relative water content, and photosynthetic efficiency, while markedly elevating malondialdehyde (MDA) content, electrolyte leakage, and antioxidant enzyme activities, including. superoxide dismutase, peroxidase, and catalase. Foliar application of ZnO-NPs (100 mg L⁻¹) effectively mitigated these adverse effects by improving vegetative growth, sustaining water status, and enhancing stomatal function. Significantly, ZnO-NPs decreased oxidative stress, as shown by lower MDA levels, membrane leakage, and concurrently decreased antioxidant enzyme activities under stress, indicating a low level of reactive oxygen species accumulation. Moreover, treatment with ZnO-NPs resulted in a significant decrease in total phenolic accumulation across the NaCl treatments with decreased activation of secondary antioxidant pathways. This trend shows that ZnO-NPs may effectively decrease cellular oxidative stress, thus limiting phenolic biosynthesis. ZnO-NPs confer enhanced salinity resilience in carnation plants by preserving physiological integrity, improving water status, photosynthetic activity, and minimizing oxidative damage. These findings highlight the potential of NP-based foliar applications as ecologically viable approaches for improving the stress resilience of ornamental species cultivated under saline stress. The current study provides a scientific basis for integrating ZnO-NPs into sustainable floriculture practices under saline stress.