TOXICITY OF COPPER AND ZINC IN SEEDLINGS OF MUNG BEAN AND INDUCING ACCUMULATION OF POLYAMINE

A solution culture was conducted to investigate the effects of copper (Cu) and zinc (Zn) toxicity on growth of mung bean (Phaseolus aures Ro xb. cv VC-3762) and accumulation of polyamine. Eight-day-old seedlings were grown in diluted nutrient solution with different concentrations of Cu and Zn for 6 days. Results showed that elongation of epicotyl a nd fresh weight of plants were decreased by 10 mu M Cu and 100 mu M Zn significantly compared to control (0.03 mu M Cu and 0.1 mu M Zn). Acc umulation of polyamine, especially putrescine (Put) was found in the e picotyl of mung bean seedlings. Addition of 5 mM calcium (Ca) into nut rient solution improved the growth of 10 mu M Cu-treated seedling, and decreased the concentration of Put and increased concentrations of sp ermine and spermidine in epicotyl of plants. Moreover, supplying Put d id not increase tolerance of plant to Cu or Zn. It was suggested that Put accumulation resulting from toxicity of Cu and Zn might merely be a symptom of stress injury.