文摘
Nanoparticles (NPs) have been reported to cause physiological effects on plant cells and tissue. This study traced the uptake and distribution of magnetic iron oxide nanoparticles (γ-Fe2O3 NPs) in citrus (Citrus reticulata) plants under hydroponic condition by fluorescent dye labeled γ-Fe2O3 NPs, and described a detailed evidence of physiological effects of 0–100 mg/L γ-Fe2O3 NPs on citrus plants by measuring the physiological parameters such as content of chlorophyll, malondialdehyde (MDA), soluble sugar, soluble protein, activity of antioxidant enzyme, and ferric reductase after 21 days exposure. Fluorescence images of citrus stem and root showed that citrus roots could absorb γ-Fe2O3 NPs but no translocation from roots to shoots was observed, since NPs aggregated or even clogged the vascular system. Physiological results showed that 20 mg/L γ-Fe2O3 NPs could significantly enhance chlorophyll content by 126.4%, while 50 and 100 mg/L of γ-Fe2O3 NPs decreased chlorophyll content by 27.8 and 35.4%, respectively. MDA contents in citrus leaves under 20–100 mg/L γ-Fe2O3 NPs exposure were increased by 37.8, 107.2, and 61.5%, respectively, while that in roots were decreased by 27.0,11.9, and 7.4%, respectively, with elevated SOD and CAT activity, suggesting that oxidative stress occurred in citrus leaves, but oxidative stress in roots was eliminated by antioxidant defense. It is noteworthy that although Fe(II)-EDTA treatment had a high level of chlorophyll content, it induced strong oxidative stress in citrus plants as well. Collectively, the various physiological responses of citrus plants to γ-Fe2O3 NPs exposure were closely correlated with the concentrations of NPs. γ-Fe2O3 NPs at proper concentrations, such as 20 mg/L, have the potential to ameliorate chlorosis of plants and be effective nanofertilizers for increasing agronomic productivity.