| Popis: |
Cultivation experiments, including short-term copper uptake kinetics, uptake kinetics of Cu by different subcellular fractions and efflux of Cu, were carried out to investigate mechanisms of copper uptake by two species of submerged macrophyte, Hydrilla verticillata (L. f. ) Royle and Myriophyllum spicatum L. The results showed that: (1) Both H. verticillata and M. spicatum showed high influx rates for copper ions with no statistically significant differences [ Vmax (DW) is 2 micromol. (g min) - 1] ; (2) Both leaf and stem Cu concentrations of two strains of plants showed sharp increase with the external medium, and the equilibrium was reached for about 12 h after being exposed to solution with 2 micromol L-1 Cu. Leaves of these two plants accumulated much higher concentrations of Cu than stems. Furthermore, Cu in leaves concentrated predominantly in cell walls (60% ) , followed by soluble and organell fractions; (3) Copper accumulated in cell wall of H. verticillata leaf was considerably higher than that of M. spicatum, and Cu concentrated in intracellular fractions of leaves showed no statistically significant difference between these two plants. Moreover, ability of Cu accumulation and efflux by H. verticillata was higher than that by M. spicatum. |
