Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
School of Geography, Earth and Environmental Science, University of Birmingham, Edgbaston, B15 2TT Birmingham, U.K.
Environ Sci Technol. 2020 Mar 17;54(6):3181-3190. doi: 10.1021/acs.est.9b05794. Epub 2020 Mar 4.
The mechanism of graphene-based nanomaterial (GBM)-induced phytotoxicity and its association with the GBM physicochemical properties are not yet fully understood. The present study compared the effects of graphene oxide (GO) and reduced GO (rGO) on rice seedling growth under hydroponic conditions for 3 weeks. GO at 100 and 250 mg/L reduced shoot biomass (by 25 and 34%, respectively) and shoot elongation (by 17 and 43%, respectively) and caused oxidative damage, while rGO exhibited no overt effect except for the enhancement of the antioxidant enzyme activities, suggesting that the surface oxygen content is a critical factor affecting the biological impacts of GBMs. GO treatments (100 and 250 mg/L) enhanced the iron (Fe) translocation and caused excessive Fe accumulation in shoots (2.2 and 3.6 times higher than control), which was found to be the main reason for the oxidative damage in shoots. GO-induced acidification of the nutrient solution was the main driver for the Fe overload in plants. In addition to the antioxidant regulators, the plants triggered other pathways to defend against the Fe toxicity via downregulation of the Fe transport associated metabolites (mainly coumarins and flavonoids). Plant root exudates facilitated the reduction of toxic GO to nontoxic rGO, acting as another route for plant adaption to GO-induced phytotoxicity. This study provides new insights into the mechanism of the phytotoxicity of GBMs. It also provides implications for the agricultural application of GBM that the impacts of GBMs on the uptake of multiple nutrients in plants should be assessed simultaneously and reduced forms of GBMs are preferential to avoid toxicity.
基于石墨烯的纳米材料（GBM）诱导植物毒性的机制及其与 GBM 物理化学性质的关系尚不完全清楚。本研究比较了水培条件下 3 周内氧化石墨烯（GO）和还原氧化石墨烯（rGO）对水稻幼苗生长的影响。100 和 250 mg/L 的 GO 分别降低了 shoot 生物量（分别降低了 25%和 34%）和 shoot 伸长（分别降低了 17%和 43%），并导致氧化损伤，而 rGO 除了增强抗氧化酶活性外，没有明显的作用，表明表面氧含量是影响 GBM 生物影响的关键因素。GO 处理（100 和 250 mg/L）增强了铁（Fe）的转运，并导致 shoot 中 Fe 过度积累（比对照高 2.2 和 3.6 倍），这被发现是 shoot 中氧化损伤的主要原因。GO 诱导的营养液酸化是植物 Fe 过载的主要驱动因素。除了抗氧化调节剂外，植物还通过下调与 Fe 转运相关的代谢物（主要是香豆素和类黄酮）来触发其他途径来抵御 Fe 毒性。植物根分泌物促进了有毒 GO 向无毒 rGO 的还原，作为植物适应 GO 诱导的植物毒性的另一种途径。本研究为 GBM 植物毒性的机制提供了新的见解。它还为 GBM 在农业中的应用提供了启示，即应同时评估 GBM 对植物多种养分吸收的影响，并且应优先使用还原形式的 GBM 以避免毒性。
