Biofortification of bok choy with selenium nanoparticles and its inhibitory effects on cadmium accumulation

Background and aimsCadmium (Cd) contamination poses a potential threat to plant growth and human health. In this study, we aimed to determine the effect of selenium nanoparticles (SeNPs) on Cd and selenium (Se) uptake and accumulation in bok choy, and investigate the detoxification mechanism of SeNPs on bok choy under Cd stress.MethodsA pot culture was performed in Cd-contaminated soil with soil applied and foliar-sprayed SeNPs, including SLow, SHigh, FLow, FHigh, and corresponding control treatment. The soil available Cd content, Cd and Se fractions in soil, elements accumulation, subcellular Cd/Se distribution, MDA content, SOD activity, and Fourier transformed infrared spectroscopy (FTIR) were evaluated.ResultsSoil applied SeNPs significantly reduced Cd concentration by 25.9-42.4%, and Cd uptake rate by 33.4-37.8%. Further, soil applied SeNPs had no significant effect on available Cd but did affect Se fractions in soil. Additionally, soil applied SeNPs increased Se concentration by 3.1 - 6.3 times in bok choy and caused a higher Se concentration in root than in shoot, with the residual and organic matter-bound Se mainly affecting Se accumulation in shoot. However, foliar-sprayed SeNPs had no significant effect on Cd uptake but increased Se accumulation by 2.4 - 33.0 times in bok choy. Soil applied and foliar-sprayed SeNPs prompted the distribution of Cd in cell wall and in soluble component in shoot, respectively, which reduced the damage of Cd on organelle.ConclusionSoil applied SeNPs was an effective method for reducing Cd accumulation and improving Se biofortification and mineral elements accumulation in bok choy.