Effect of graphene oxide on copper stress in Lemna minor L.: evaluating growth, biochemical responses, and nutrient uptake

•Low concentration (5-20 μM) of Cu enhanced the accumulation of Cu, B, Mn, Fe, Co, and Zn, but decreased P uptake.•GO neutralized the effects of Cu on nutrient accumulation in Lemna minor.•GO at a concentration of 5 mg/L decreased the damages caused by stress of Cu.

The wide application and unique properties of graphene oxide (GO) make it to interact with other pollutants and subsequently alter their behavior and toxicity. We evaluated the influences of GO at different concentrations (1 and 5 mg/L) on copper (Cu) stress in duckweed (Lemna minor L.) GO below a concentration of 5 mg/L showed no adverse effects on L. minor. The addition of Cu above 10 μM represented a stress condition, which was evidenced by various parameters such as frond number, percent inhibition of growth rate (Ir), total chlorophyll content, dry weight, superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD). When L. minor was simultaneously exposed to GO and Cu, especially at a GO concentration of 5 mg/L and a Cu level above 10 μM, the increase of Ir and decrease of chlorophyll content were inhibited, suggesting that the Cu stress was diminished in the presence of GO. The addition of Cu alone, ranging between 5 and 20 μM, increased Cu, B, Mn, Fe, Co, and Zn uptake, but decreased P uptake. Our results suggest that GO can lessen Cu stress in L. minor via Cu adsorption, thereby protecting the plants from the damaging effects of high Cu concentrations.

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