Environmentally Friendly Synthesis of Silver Nanoparticles (AgNPs) Using Mentha arvensis Plants Modulates Physiological and Biochemical Attributes and Yield of Sunflower (Helianthus annuus L.)

Green nanotechnology has emerged as a viable option for the production of nanoparticles. The present study aims to synthesize silver nanoparticles using Mentha arvensis leaves and evaluate the effects of varying concentrations of AgNPs (0, 5, 15, and 25 mg L-1) used as seed treatment, foliar spray, and seed + foliar spray to improve sunflower growth, yield attributes, physiological, metabolic, and biochemical aspects. The AgNPs, characterized by well-defined peaks signaling cubic symmetry, were biologically synthesized using M. arvensis, as validated through X-ray diffraction analysis. The results showed that 25 mg L-1 foliar application of AgNPs significantly enhanced shoot length (35.2%), leaf number (70.4%), root length (45.9%), shoot fresh weight (57.3%), shoot dry weight (62.08%), root fresh weight (30.3%), root dry weight (22.8%), chlorophyll a (196.1%), chlorophyll b (182.3%), carotenoid (271.8%), total soluble protein (26.8%), soluble sugar (42.3%), proline (76.1%), phenol (71.5%) contents, antioxidant enzyme activities and head diameter (62.73%), head weight/plant (39.5%), seed yield/ plant (58.2%), and the weight of 100 seeds (78.02%). Furthermore, this treatment positively influenced seed quality parameters such oil content, crude protein content, and a substantial reduction in seed moisture content. Fatty acid composition analysis revealed significant changes, with remarkable increases in linoleic acid (52.04%), oleic acid (26.8%), and a substantial decrease in palmitic acid (42.4%) in response to foliar spray with 25 mg L-1 AgNPs. Foliar spray with 25 mg L-1 AgNPs proved to be the most efficient methods and can be a sustainable fertilizer and impact the yield and quality of the seeds.