Physiological effects of high copper concentration on poplar plants

摘要

The effect of high levels of copper was studied on poplar plants (P. x euramericana) Adda clone grown in the presence of 0.4 (control), 20, 100, 500 e 1000 μM Cu~(2+). The effect of copper on plant growth was evaluated by determining the dry mass of leaves, stalks, stem, roots and by measuring stem length and stem diameter after 15 or 34 days from the beginning of the experiment. The response of photosynthetic apparatus was determined through gas exchange and chlorophyll fluorescence measurements. Increasing levels of copper resulted in a general reduction in plant growth. The dry mass and the stem length showed a drastic reduction at copper concentration of 100 μM, while that of roots displayed a more gradual decrease. At concentrations of 500 and 1000 μM, toxicity symptoms were observed as necrosis and shedding of leaves, and a strong reduction in plant growth. At these latter Cu~(2+) concentrations, main parameters derived from A/C_i curves were also markedly inhibited. Poplar plants tolerated 20 μM Cu~(2+), indicating a range for tolerance between 20 and 100 μM, and marked symptoms of damages to the photosynthetic apparatus at 1000 μM.