Alleviation of arsenic stress in pakchoi by foliar spraying of engineered nanomaterials.

Addressing heavy metal contamination in leafy vegetables is critically important due to its adverse effects on human health. In this study, we investigated the inhibitory effects of foliar spraying with four nanoparticles (CeO, ZnO, SiO, and S NPs) on arsenic (As) stress in pakchoi (Brassica rapa var. Chinensis). The findings reveal that foliar application of ZnO NPs at 1 ~ 2.5 mg plant and CeO NPs at 5 mg plant significantly reduces As in shoots by 40.9 ~ 47.3% and 39.4%, respectively. Moreover, 5 mg plant CeO NPs increased plant height by 6.06% and chlorophyll a (Chla) content by 30.2% under As stress. Foliar spraying of CeO NPs at 0.2-5 mg plant also significantly enhanced superoxide dismutase (SOD) activity in shoots by 9.4 ~ 13.9%, lowered HO content by 42.4 ~ 53.25%, and increased root protein contents by 79 ~ 109.2%. CeO NPs regulate the As(III)/As(V) ratio, aiding in As efflux from roots and thereby reducing As toxicity to plants. In vitro digestion experiments reveal that the consumption of CeO NPs carries the lowest health risk of As. In addition, foliar spraying of ZnO NPs at 1 ~ 2.5 mg plant can suppress plant As uptake by modulating enzyme activity, reducing leaf damage, and enhancing chlorophyll content. The study demonstrates that high CeO NP concentrations and suitable ZnO NP concentrations can alleviate As toxicity in pakchoi, consequently reducing human health risks.