ABSTRACT
Soil salinity is a worldwide challenge, especially detrimental to cowpea growth in Nigeria, with origins in factors like excessive irrigation, soil degradation, and climate change, resulting in heightened soil sodium chloride (NaCl) levels. This disrupts plant physiology, leading to stunted growth, decreased yields, and compromised nutrition. To address this, biosynthesized copper nanoparticles (Cu NPs) via nanotechnology were investigated as a potential remedy. Cowpea seeds were planted in soils exposed to 0, 625, 1250, and 2500ppm NaCl concentrations. Subsequently, cowpea seedlings received foliar sprays of biosynthesized Cu NPs, prepared using leaf extracts from Hibiscus sabdariffa, Carica papaya, and Azadiractha indica at varying concentrations (5, 25, and 50 %). Results revealed the adverse impact of NaCl on cowpea growth but highlighted the substantial improvements achieved through biosynthesized nanoparticles. Particularly under low salinity conditions (625ppm), cowpea vine length responded positively to treatments. Vines treated with Hibiscus sabdariffa, Carica papaya, and Azadiractha indica at a 50% concentration showed significant increases in vine length. Other growth parameters such as leaf area, leaf count, and internode length also exhibited significant differences compared to control groups (p<0.05). Enzymatic activity results (CAT and POD) highlighted intricate interactions between copper nanoparticles from various plant extracts and the enzymatic antioxidant systems in cowpea plants. The highest total carotenoid content (56 mg/g) was observed in the nanoparticle treatment (C.P. 25%), with the highest lycopene levels (43.68 mg/g) found in treatments involving H.S 25%, H.S 50%, C.P 5%, and C.P 25%. These findings emphasize the significance of biosynthesized nanoparticles in promoting cowpea growth and productivity, particularly in salinity-stressed conditions, the potential of nanotechnology to bolster resilient, high-yield crop development, thereby addressing global food xv security amidst evolving environmental challenges. Further research is recommended to study mechanisms of these interactions at molecular level and optimize nanoparticle applications for enhancing phytonutrient production in crops.
