University of Birjand-Research Group of Drought and Climate Change Journal of Drought and Climate change Research 3092-6076 4 1 2026 05 22 Effects of Foliar Application of Zinc Oxide Nanoparticles on Morphophysiological and Bochemical Responses of Catharanthus Roseus (L.) G. Don under Water Deficit Stress Effects of Foliar Application of Zinc Oxide Nanoparticles on Morphophysiological and Bochemical Responses of Catharanthus Roseus (L.) G. Don under Water Deficit Stress 203 226 3817 10.22077/jdcr.2025.10186.1176 FA Haniyeh Haq Nari Ms.C. Graduate in Ornamental Plants, Department of Horticultural Sciences, Faculty of Agriculture, Lorestan University, Lorestan, Iran 0009-0006-2797-5846 Abdolhossein Rezaei Nejad Professor of Ornamental Plant Physiology, Department of Horticultural Sciences, Faculty of Agriculture, Lorestan University, Lorestan, Iran 0000-0002-5428-3697 Farhad Beiranvand Ph.D. in Horticultural Sciences – Physiology of Ornamental Plants. Department of Horticultural Sciences, Faculty of Agriculture, Lorestan University, Lorestan, Iran Nahid Zomorrodi Ph.D. in Horticultural Sciences – Physiology of Ornamental Plants. Department of Horticultural Sciences, Faculty of Agriculture, Lorestan University, Lorestan, Iran Journal Article 2025 10 02 The present study aimed to investigate the effects of foliar application of zinc oxide nanoparticles (ZnO-NPs) on the morphological and physio-biochemical traits of the ornamental–medicinal plant periwinkle [Catharanthus roseus (L.)] under water deficit stress. The experiment was conducted as a factorial arrangement based on a completely randomized design) with four replications. The first factor was water deficit at three levels (80%, 50%, and 20% of available water content), while the second factor consisted of foliar application of ZnO-NPs at four concentrations (0, 50, 100, and 200 µM), applied as a pre-treatment at the four-leaf stage. The experiment continued until full flowering (two months), after which morpho-physiological parameters (plant height, stem length and diameter, leaf number, root volume and length, fresh and dry weights of stems, leaves, and roots, gas exchange parameters, relative water content (RWC), and electrolyte leakage (EL)) as well as biochemical traits (malondialdehyde (MDA) content, proline content, photosynthetic pigments concentration, and the activities of catalase, peroxidase, and ascorbate peroxidase) were measured. The results demonstrated that water deficit stress significantly reduced plant height, leaf area, RWC, photosynthetic pigments concentration, fresh and dry biomass, and gas exchange, while increasing EL, MDA content, proline accumulation, and antioxidant enzyme activities. In contrast, foliar application of ZnO-NPs enhanced antioxidant enzyme activity, RWC, photosynthetic pigments, and gas exchange, thereby improving plant tolerance to drought stress. Among the tested concentrations, 50 and 100 µM ZnO-NPs were the most effective in alleviating the adverse effects of water deficit and promoting plant growth under stress conditions. The present study aimed to investigate the effects of foliar application of zinc oxide nanoparticles (ZnO-NPs) on the morphological and physio-biochemical traits of the ornamental–medicinal plant periwinkle [Catharanthus roseus (L.)] under water deficit stress. The experiment was conducted as a factorial arrangement based on a completely randomized design) with four replications. The first factor was water deficit at three levels (80%, 50%, and 20% of available water content), while the second factor consisted of foliar application of ZnO-NPs at four concentrations (0, 50, 100, and 200 µM), applied as a pre-treatment at the four-leaf stage. The experiment continued until full flowering (two months), after which morpho-physiological parameters (plant height, stem length and diameter, leaf number, root volume and length, fresh and dry weights of stems, leaves, and roots, gas exchange parameters, relative water content (RWC), and electrolyte leakage (EL)) as well as biochemical traits (malondialdehyde (MDA) content, proline content, photosynthetic pigments concentration, and the activities of catalase, peroxidase, and ascorbate peroxidase) were measured. The results demonstrated that water deficit stress significantly reduced plant height, leaf area, RWC, photosynthetic pigments concentration, fresh and dry biomass, and gas exchange, while increasing EL, MDA content, proline accumulation, and antioxidant enzyme activities. In contrast, foliar application of ZnO-NPs enhanced antioxidant enzyme activity, RWC, photosynthetic pigments, and gas exchange, thereby improving plant tolerance to drought stress. Among the tested concentrations, 50 and 100 µM ZnO-NPs were the most effective in alleviating the adverse effects of water deficit and promoting plant growth under stress conditions. https://jdcr.birjand.ac.ir/article_3817_fa6c94460e902005a0b660266190c8ba.pdf