Comparative investigation on chemical and green synthesized titanium dioxide nanoparticles against chromium (VI) stress eliciting differential physiological, biochemical, and cellular attributes in Helianthus annuus L

Abstract

Nanotechnology is a new scientific area that promotes unique concepts to comprehend the optimal mechanics of nanoparticles (NPs) in plants under heavy metal stress. The present investigation focuses on effects of synthetic and green synthesized titanium dioxide nanoparticles (TiO₂ NPs and gTiO₂ NPs) against Cr(VI). Green TiO₂ NPs have been produced from plant leaf extract (Ricinus communis L.). Synthesis was confirmed employing an array of optical spectroscopic and electron microscopic techniques. Chromium strongly accelerated H₂O₂ and MDA productions by 227 % and 266 % at highest chromium concentration (60 mg/kg of soil), respectively, and also caused DNA damage, and decline in photosynthesis. Additionally, anomalies were observed in stomatal cells with gradual increment in chromium concentrations. Conversely, foliar applications of TiO₂ NPs and gTiO₂ NPs considerably mitigated chromium stress. Sunflower plants treated with modest amounts of green TiO₂ NPs had significantly better growth index compared to chemically synthesized ones. Principal component analysis highlighted the variations among photosynthetic attributes, oxidative stress markers, and antioxidant defense systems. Notably, gTiO₂ supplementation to the Cr(VI) strained plants minimized PC₃ production which is a rare report so far. Conclusively, gTiO₂ NPs have been identified to be promising nano-based nutrition resource for farming applications.

Keywords: Ascorbate-glutathione; Gene expression; Photosystem II; Phytochelatins; Phytoremediation; Reactive oxygen species; Seed germination; Transpiration.