Graphene effects on Populus nigra: assessment of sex-specific adaptive responses by in vitro culture

The application of graphene-related materials (GRMs) has increased considerably in various fields, posing a potential environmental risk. However, little is known about sex-related responses to GRMs in dioecious woody plants and in that regard, callus culture represents a reliable tool for toxicity and tolerance studies. In this work, the effects of different concentrations of graphene oxide (GO) and graphene nanoplatelets (GNP) on physiological traits of male and female clones of Populus nigra were investigated. After a 3-week treatment, at high concentrations, GO promoted in female calli, an increase in fresh weight and a reduction in protein content, accompanied by a remarkable enhancement of APX and CAT activity while no toxic effect was observed under GNP treatment. Instead, male cells displayed a greater sensitivity at lower GO concentration (25 mg/L), exhibiting a notable reduction in biomass, nutrient uptake and protein content, associated to an increase in APX and CAT activity. Similarly, at 25 mg/L, GNP caused a slight enhancement in lipid peroxidation (MDA) level and a significant decrease in protein content, accompanied by an increase in the production of flavonoids. These findings revealed sexually different responses to GO and GNP, with female clone exhibiting more tolerance compared to male one.