Physiological and Biochemical Characteristics of Cinnamomum camphora in Response to Cu- and Cd-Contaminated Soil

Copper (Cu) and cadmium (Cd) are ordinary heavy metals. Unreasonable development and utilization of these heavy metals will cause severe pollution to the soils and consequently bring damage to human health. Therefore, recovering soils polluted by heavy metals is crucial. An indoor pot experiment was carried out involving seven treatments, namely, low-concentration Cu stress (Cu1), high-concentration Cu stress (Cu2), low-concentration Cd stress (Cd1), high-concentration Cd stress (Cd2), low-concentration Cu-Cd combined stress (Cu1Cd1), and high-concentration Cu-Cd combined stress (Cu2Cd2), and an uncontaminated soil as a control. Results demonstrated that the net photosynthetic rate and chlorophyll content are approximately 8.36-72.51% and 7.22-36.50%, respectively, lower under the Cu, Cd, and Cu-Cd combined stresses than under the control. The net photosynthetic rates are higher under Cu2 and Cd2 than under Cu1 and Cd1; by contrast, the net photosynthetic rate of leaves is lower under Cu2Cd2 than under Cu1Cd1. The net photosynthesis rate of Cinnamomum camphora is significantly positively correlated with superoxide dismutase activity but is significantly negatively correlated with the total chlorophyll, malondialdehyde, soluble sugar, and proline contents. Young Cinnamomum camphora grows well under Cu, Cd, and Cu-Cd combined stresses and is applicable in ecologically restoring heavy metal-contaminated soils.