Nano-silicon mediated alleviation of Cd toxicity by cell wall adsorption and antioxidant defense system in rice seedlings

Purpose Heavy metal, particularly cadmium (Cd) is toxic to rice growth. Studies showed that nano-silicon particles (SiNPs) can alleviate Cd toxicity. However, underlying mechanisms especially cell wall adsorption and different forms of pectin are rarely investigated. Methods In this experiment, the impacts of foliar application of SiNPs (2.5 mM) were investigated to alleviate Cd stress (50 mu M) in rice and to study the role of SiNPs in reducing Cd-induced inhibition of plant growth, antioxidant defense systems, Cd translocation, and cell wall adsorption. Results The results exhibited that Cd toxicity inhibited rice growth and biomass accumulation, meanwhile leaves had high concentrations of Cd. However, foliar application of SiNPs improved root and shoot growth. Moreover, Cd concentration was reduced in the leaves of rice seedlings. The results of Fourier Infrared Spectroscopy (FTIR) showed that SiNPs enhanced peak values of polysaccharides. In addition, X-ray photoelectron spectroscopy (XPS) showed high Cd contents in the roots of rice seedlings. Cell wall showed high concentrations of Cd, moreover, enhancement of antioxidant defense mechanism and the alleviation of oxidative stress symptoms in leaves by SiNPs may be directly related to the decrease of Cd concentration in leaves. Conclusion Altogether, our study results show that SiNPs can alleviate Cd toxicity in rice seedlings by reducing Cd uptake and enhancing cell wall Cd adsorption and antioxidant defense system.