Synthesis and optimization of nanoparticles from Phragmites karka improves tomato growth and salinity resilience

Halophytes contain many secondary metabolites that can facilitate the capping and stabilizing of nanoparticles. Synthesis and optimization of zinc oxide nanoparticles from Phragmites karka were performed for the first time in this study to assess the salinity resilience of tomato seedlings in 100 mM NaCl using biotechnological applications and growth analysis. Response surface methodology and central composite design data revealed that ZnO NPs were stable at a 2:1 ratio of plant and salt concentration (pH of 6.5 at 37.5 degrees C). The peak obtained at 331 nm from UV-Vis spectroscopy confirmed the synthesis of ZnO NPs and these NPs have multiple functional groups. The chemical bond formation of the prepared ZnO NPs (assessed using FTIR and XRD) confirmed the crystalline structure of ZnO NPs that were derived from halophyte P. karka. The SEM images revealed that ZnO NPs have a particle size of 23.5 nm and are spherical, while DLS revealed the size (32.6 nm) and zeta-potential (-6.43 mV) of nanoparticles. Plants treated with ZnO NPs increase the overall tomato growth parameters under salt stress, including shoot length (3-fold), especially at T20 (50 mgL-1 ZnO NPs + 100 mM NaCl) treatment among all growth weeks. The number of leaves increased at T16 (20 mgL-1 ZnO NPs + 100 mM NaCl). The numbers of nodes and internodes were increased at T20 (50 mgL-1 ZnO NPs + 100 mM NaCl) in both parameters. Halophytic nanoparticles could be beneficial sources of biostimulants to improve salt resilience of tomato plants undergoing salt stress.