Growth and physiological response of Cinnamomum camphora (L.) Presl to copper stress and analysis of copper enrichment and transport characteristics

This study investigated copper-resistant Cinnamomum camphora (L.) Presl in the restoration of a copper-polluted mining area through pot simulation experiments. Six treatment concentrations were established (50, 150, 300, 600, 900, and 1 200 mg/kg), with no copper addition used as the control (CK). After 60 d of treatment, biomass accumulation, chlorophyll content, physiological and biochemical indexes of C. camphora, and copper ion accumulation and transfer were measured. The impact of different copper concentrations on growth, physiological, and biochemical responses in C. camphora, as well as the patterns of copper accumulation and distribution in various tissues, were explored to evaluate copper tolerance in this species. Results showed that C. camphora growth under copper stress was enhanced at low copper concentrations (150 mg/kg) and inhibited at high copper concentrations. Physiological indicators, including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), hydrogen peroxide (H₂O₂), free proline, and soluble sugar, did not significantly increase under 900 mg/kg copper treatment. glutathione reductase (GR) decreased gradually with the increase of copper concentration, while malondialdehyde (MDA) and glutathione (GSH) contents increased gradually with the increase of copper concentration. Copper was predominantly accumulated in the roots, minimizing toxicity to above-ground tissues, with organ copper content in the order root > leaf > stem. The copper transfer rate (IF) from root to leaf (leaf/root) decreased from 0.078 in the control to 0.007 in the 1 200 mg/kg copper treatment group, while the copper transfer rate (IF) from root to stem (Stem/Root) decreased from 0.06 in the control to 0.005 in the 1 200 mg/kg copper treatment group. Based on growth performance, physiological responses, and copper ion accumulation and transfer, C. camphora exhibited good copper tolerance, withstanding up to 900 mg/kg, highlighting its potential for planting in copper-contaminated soils.