Effects of zinc oxide nanoparticle application methods on growth, photosynthesis, zinc, and cadmium accumulation in <i>Triticum aestivum</i> (L.)

The application of zinc oxide nanoparticles (ZnONPs) often affects the cadmium (Cd) uptake by plants; however, the relative efficiencies of different ZnONP application methods on Cd and zinc (Zn) uptake by plants need to be studied. The current study compared the efficiency of three ZnONP application methods [soil, foliar, and soil + foliar (S + F)] in terms of wheat plant growth and Cd/Zn uptake. The methods of ZnONP application caused significant variations in plant growth, photosynthetic pigments, oxidative stress, Zn and Cd uptake. The combined S + F method of ZnONP application was more effective in enhancing growth, Zn concentration and reducing Cd content in grains as compared to other methods. The S + F method increased the grain yield by 148.9% and Zn contents in grains by 72.8% compared to the control. Combined S + F application method reduced Cd concentrations in shoots, roots and grains by 12.7%, 20%, and 37.7%, respectively, compared to soil application method. Furthermore, compared to foliar application method, this decrease was 15.3%, 16.6%, and 31% for shoots, roots, and grains, respectively. Our results demonstrate that the S + F application of ZnONPs is more effective at reducing grain Cd contents in wheat, enhancing Zn biofortification for the nano-enabled production of safer food crops.