**4. Nanoparticles and other environmental stresses**

Titanium oxide nanoparticles play a substantial role in the mitigation of light stress in crops as they catalyze the oxidation-reduction reaction, which then forms superoxide anion radicals and hydroxides. Oxidative stress is induced by ultraviolet (UV) light and has a negative impression on the growth of the plant. UV-B produces H2O2 and superoxide radicals and enhanced the leakage of electrolytes and lipid peroxidation, which leads to reduce the photosynthesis rate and normal leaf structure is also deteriorated [81]. In wheat plants, Silicon NPs increase antioxidant activities for the regulation of oxidative stress after UV-B exposure [82]. Herbicides are used to control weeds in agroecosystems. A methyl viologen herbicide, Paraquat is used extensively to control weeds in rice. Multiwall carbon nanotubes can modulate the toxicity of Paraquat [50], which promotes lateral root growth and photosynthesis in *Arabidopsis* and protect against the toxicity of Paraquat by lowering its bioavailability and promoting the oxidative-stress-related protein expression and photosynthesis. Therefore, the NPs can modulate abiotic stress-induced responses in plant growth at different levels. However, their physiochemical, electrical, optical, and biological properties are crucial [83]. Plants' tolerance to low temperature in green beans is increased by the exogenous application of Ag NPs [84] as they are used to reduce the oxidative stress in wheat.
