Mitigation of salinity stress in sunflower plants (Helianthus annuus L.) through topical application of salicylic acid and silver nanoparticles

Salinity stress poses a significant threat to sunflower (Helianthus annuus L.) by impairing water and nutrient uptake, disrupting cellular functions, and increasing oxidative damage. This study investigates the impact of Salicylic acid (SA) and silver nanoparticles (AgNPs) on growth, biochemical parameters, and oxidative stress markers in salt-stressed sunflower plants. Experiments were conducted in a controlled greenhouse environment at the Islamia University of Bahawalpur, Pakistan, using sunflower seeds (Orisun 701). AgNPs were synthesized using neem leaf extract and characterized through SEM, FTIR, zeta potential analysis, and XRD. Treatments included foliar application of SA (10 mM) and AgNPs (40 ppm) under 100 mM sodium chloride-induced salt stress. Growth metrics, antioxidant enzyme activities, chlorophyll content, and oxidative stress markers (H₂O₂ and MDA levels) were measured to evaluate treatment effects. The SA and AgNP treatments improved sunflower growth under salt stress, with AgNPs showing a greater impact. SA increased shoot fresh weight by 16.4%, root fresh weight by 6.9%, and chlorophyll content by 12.7%, while AgNPs enhanced shoot fresh weight by 30.5%, root fresh weight by 11.6%, and total chlorophyll by 80%. AgNPs also significantly reduced H₂O₂ by 42.7% and MDA by 34.6%, indicating reduced oxidative damage. Cluster analysis further demonstrated the distinct physiological responses elicited by AgNPs compared to SA. SA and AgNPs enhance sunflower resilience to salinity, with AgNPs showing a particularly strong effect on chlorophyll content and oxidative stress markers. These findings highlight the potential of SA and AgNPs as effective treatments for salt stress, suggesting further research across different crops and environments.