Single and combined toxicity of chromium and copper to seed germination and root elongation of Pakchoi (Brasica chinensis) in soils.

[Objective] The elements Cu and Cr are two important heavy metal pollutants.In this study the single and combined effects of Cu and Cr(Ⅵ) on the seed germination and the root elongation of Pakchoi(Brassica chinensis) were investigated in order to provide scientific basis for the predication,evaluation and repair of copper and chromium combined pollution.[Method] With the seeds of pakchoil Qinbai 2 as material,the soil culture experiments were conducted to study the effects of single and combined pollution of copper and chromium on seeds germination energy,germination rate and root inhibition ratio.[Result] The results showed that seed germination indexes were not significantly affected in low concentrations of Cu and Cr treatments,whereas the root enlogation inhibition rate was remarkable in high concentrations of Cu(≥800 mg/kg) and Cr(≥60 mg/kg) treatments(P0.05).It was found that there were significant liner relationships between concentration of Cr(Ⅵ) and root elongation(P0.01) and low concentration of Cu(≤200 mg/kg) could accelerate the root elongation while high concentration of Cu could inhibit it significantly.Cu and Cr had antagonistic effects on seeds germination and root elongation of Pakchoi Meanwhile,the antagonism of Cu against Cr was in response to the concentration of Cu.[Conclusion] In conclusion,the toxicity of the pollutants to seed germination is lower than to root elongation.It's suggested that the seed root length inhibition rate be taken as indicator to determine heavy metal biological toxicity