Enhanced bioaccumulation efficiency and tolerance for Cd (Ⅱ) in Arabidopsis thaliana by amphoteric nitrogen-doped...

Amphoteric nitrogen-doped carbon dots (N-CDs) that prepared environmentally friendly have rich functional groups, such as carboxyl, amino, hydroxyl, carbonyl, etc. Through electrostatic attraction and complexation between the chemical groups and metal ions, N-CDs present excellent adsorption capacity for Cd²⁺ in heavy polluted water with the saturated adsorption weight of 559  mg g^-1. The investigation of interaction between N-CDs, Cd²⁺ and Arabidopsis thaliana reveals that N-CDs (from 4  mg kg^-1 to 8  mg kg^-1) can dramatically enhance Cd bioaccumulation of plants by 58.3% of unit biomass and 260% of individual seedling when the plants were cultivated for 10 days under Cd stress (from 10 mg kg^-1 to 50 mg kg^-1). Simultaneously, N-CDs significantly alleviate the toxicity caused by high Cd stress on Arabidopsis thaliana seedlings growth. N-CDs induce higher germination rate (maximum: 2.5-fold), higher biomass (maximum: 3.7-fold), better root development (maximum: 1.4-fold), higher photosynthetic efficiency and higher antioxidant capacity in plants under Cd stress. When the Cd and N-CDs concentration are respective 20 mg kg-1 and 4 mg kg-1, the enzyme activities of the catalase and peroxidase increased to 2.73-fold and 1.45-fold, respectively. This research prove the potential application of amphoteric N-CDs in phytoremediation because N-CDs greatly mitigate the growth retardation of plant caused by Cd²⁺ even with the extremely increased Cd²⁺ concentration in vivo.