Effect of the foliar application of biogenic-ZnO nanoparticles on physio-chemical analysis of chilli (Capsicum annum L.) in a salt stress environment

Chilli (Capsicum annuum L.) plants are cultivated globally and are valued for their culinary use. One of the major challenges in agriculture is soil salinity, which drastically cuts down crop productivity. However, no information has been reported concerning the effects of biogenic zinc oxide nanoparticles (ZnO NPs), applied as a foliar spray, on the physio-chemical properties of chilli plants under salt stress conditions. The nanoparticles were synthesized using an extract from Acacia nilotica leaves, which acted as a stabilizing and reducing agent. The characteristics of the synthesized nanoparticles were analyzed using various techniques including UV-visible spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The pot experiment utilized a salinity level of 50 mM NaCl and tested five concentrations of ZnO NPs (0, 25, 50, 75 and 100 ppm). The results demonstrated that the highest concentration (100 ppm) significantly enhanced growth parameters, including the shoot length (38.6%) and root length (25.5%) compared to the control. Additionally, biochemical parameters such as chlorophyll content (23.3%) and phenolic content (12.5%) enhanced zinc accumulation by 38.7% and decreased oxidative stress malondialdehyde (MDA) by 54.4% and hydrogen peroxide (H₂O₂) by 33.1% as compared to the control. We can conclude that foliar application of 100 ppm of the synthesized biogenic-ZnO NPs may increase chilli growth in a salt-stress environment.