University of Tabriz Journal of Plant Physiology and Breeding 2008-5168 16 2 2026 05 30 Improvement of biochemical, photosynthetic, and morphological traits of snapdragon (Antirrhinum majus) using chitosan-coated iron oxide and silver nanoparticles 53 68 21346 10.22034/jppb.2026.71310.1405 EN Younes Pourbeyrami Hir Horticultural Sciences and Landscape Engineering Department, Faculty of Agriculture, University of Mohaghegh Ardabili, Ardabil, Iran. Sahar Sardari Horticultural Sciences and Landscape Engineering Department, Faculty of Agriculture, University of Mohaghegh Ardabili, Ardabil, Iran. Journal Article 2026 01 28 <strong>Objective: </strong>Snapdragon (<em>Antirrhinum majus</em>), a perennial species in the Scrophulariaceae family, is valued for its colorful flowers and ornamental appeal. This study aimed to evaluate the effects of chitosan‑coated iron oxide nanoparticles (chitosan‑coated IONPs) and silver nanoparticles (AgNPs) on key morphological and biochemical characteristics of this species.<br /><strong>Methods:</strong> The experiment was conducted under greenhouse conditions as a factorial arrangement in a completely randomized design with four replications. Factors included four concentrations of chitosan‑coated IONPs (0, 50, 100, and 150 µM) and four concentrations of AgNPs (0, 50, 100, and 150 mg·L⁻¹). Measured traits encompassed stem diameter, fresh weight of aerial parts, number of lateral branches, plant height, flower number and diameter, total sugars, total flavonoids, total phenolic content, antioxidant capacity [1,1‑diphenyl‑2‑picrylhydrazyl (DPPH)], stomatal conductance, and chlorophyll fluorescence indices (F₀, F_m, F_v, F_v/F₀, and F_v/F_m).<br /><strong>Results:</strong> The combined application of chitosan‑coated IONPs and AgNPs significantly enhanced vegetative growth, floral attributes, and most physiological indicators. The greatest improvements in fresh weight, plant height, and number of lateral branches were achieved with 100 µM chitosan‑coated IONPs + 50 mg/L AgNPs. The F_v/F₀ and F_v/F_m ratios were enhanced by the combination of 150 µM chitosan-coated IONPs + 150 mg/L AgNPs. Significant interaction effects were observed for total sugars, total flavonoids, and DPPH activity, with the 100 µM chitosan‑coated IONPs + 100 mg/L AgNPs treatment showing the most pronounced improvements. Total phenolic content also increased under combined nanoparticle treatments, indicating activation of the antioxidant defense system.<br /><strong>Conclusion:</strong> Overall, single or combined applications of chitosan‑coated IONPs and AgNPs improved growth performance, flowering, and antioxidant responses in snapdragon. These findings highlight the potential of nanoparticle‑based strategies for sustainable, high‑quality ornamental plant production. Future research should focus on refining optimal nanoparticle concentrations and assessing their long‑term impacts. https://breeding.tabrizu.ac.ir/article_21346_9839c9dc203a5a2ec39ffaaf4ea74aeb.pdf