Copper Uptake and Tolerance by Splendens Elsholtzia and Argyi Elsholtzia.

The application of copper (Cu)-based fungicides has led to buildup of Cu in agricultural soils. In some soils under citrus production in Florida/USA, the concentrations of Cu about 10-20 times greater than background value soils were measured due to continuous use of Cu-based fungicides. Two native plant species of China Splendens elsholtzia and Argyi elsholtzia were tested for its phytoextraction of Cu from an Alfisol spiked with seven rates of Cu (0, 50, 100, 200, 300, 400 e 500 mg kg^-1) in the form of Cu(NO₃). The objective of this study was to evaluate the potential of the hyperaccumulators for remediation of Cu contaminated soils. The dry weights of leaves, stems and roots of E. Splendens were higher than those of E. Argyi. E. Splendens concentrated higher Cu in tissues, and greater accumulation of Cu in the roots, as compared to E. Argyi.  The mean concentrations of Cu in the leaves were 66.2 and 9.9 mg kg^-1, respectively for E. Splendens and E. Argyi. The corresponding values were 124.6 and 8.6 mg kg^-1 in the stems and 1014 and 176.2 mg kg^-1 in the roots. These results indicate that E. Splendens is more tolerant to high Cu stress and more efficient in Cu uptake and concentration, thus, having greater potential of application in the phytoextraction of Cu from contaminated soils. However, both species were not efficient in Cu translocation from root to the shoot. At the high levels of Cu in the soil (> 400 mg kg^-1), both species showed some symptoms of toxicity, but more severe in E. Argyi than E. Splendens plants. These results indicate that the E. Splendens is a Cu-tolerant, and its tolerance to high Cu levels was mainly related to its capability to restrict Cu uptake and accumulation in the roots.

Keywords: Phytoremediation; Copper; Soil pollution; Splendens Elsholtzia; Argyi Elsholtzia