Abstract:

Effects of cadmium stress on absorption and distribution of mineral nutrients in poplar plants were studied using three poplar clones that were cultivated in Hoagland nutrient solution supplemented with Cd²⁺ (0, 25, 50, 100 μmol·L^-1). After 5 months of treatment, plants were harvested and cadmium (Cd), potassium (K), calcium (Ca), sodium (Na), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), molybdenum (Mo), phosphorus (P) and boron (B) in various tissues including mature leaf, ageing leaf, stem xylem and root were detected. The results showed that normal harmony among mineral elements was broken by cadmium stress, which might be one of the major reasons for cadmium potentially toxic to the plants. Under the stress of cadmium with the same concentration, the content of cadmium in tissues showed significant difference among the different poplar clones, therefore it was practicable to select the poplar clones with high capability of cadmium accumulation. The retention of cadmium in ageing leaves and roots played an important role in detoxifying cadmium. Low concentration of Cd such as 25 and 50 μmol·L^-1 promoted the absorption of mineral elements, while high concentration such as 100 μmol·L^-1 reduced the absorption of mineral elements. For a given element, its content showed the significant difference among the different poplar clones. Cadmium stress remarkably inhibited the absorption of the root to Mn, decreased the up-transfer of Zn and increased the distribution of P and Na in aboveground parts of plants. Chlorosis of the poplar plants induced by cadmium was not caused by Mg, Fe, Cu, Ca and K deficit.

Key words: cadmium stress, poplar, mineral nutrition