Cadmium accumulation and its effects on physiological characteristics of Arundo donax L. in a simulated wetland

A simulated wetland experiment was used to investigate the effect of cadmium (Cd) on the growth of Arundo donax, as well as its photosynthetic characteristics and antioxidant enzyme activities. Cd accumulation in the order of stem < roots < leaves increased gradually with increasing Cd concentrations. Due to the higher transport of Cd, its accumulation in the aboveground parts of A. donax was nearly 2 times that in belowground parts. There were no differences in physiological parameters, such as the relative chlorophyll content (SPAD), the potential (Fv/Fm) or effective (Y) photochemical efficiency of PSII, and photosynthetic rate (Pn). There were slight changes in transpiration rate (Tr), intercellular CO2 concentration (Ci) and stomatal conductivity (Gs). The activity of superoxide dismutase (SOD) was stimulated by Cd treatments, and the decrease in catalase (CAT) was compensated by the induction of peroxidase (POD) suggesting these two enzymes function concurrently to remove H2O2. These results indicate that despite the oxidative stress involved in the mechanism of Cd toxicity associated with the high transport of Cd in A. donax, its photosynthetic system was not harmed. This suggests a strong tolerance of this species to increased Cd pollution and its potential use for phytoremediation purposes in wetland environment.