[Effects of stress duration and non-toxic ions on heavy metals toxicity to Arabidopsis seed germination and seedling growth].

The study on the toxicity of heavy metals Hg2+, Cd+, Cu2+ and Pb2+ to Arabidopsis se d germination and seedling growth showed that the test heavy metals had a stronger toxicity on seedling growth than on seed germination. The toxicity on seedlings was in order of Cu2+ > Hg2+ > Cd2+ /Pb2+, while on seeds was Hg2+ > Cd2+ > Pb2+/Cu2+. Seed germination rate was decreased with increasing stress duration, and different heavy metals showed different toxicity at different stress duration. For example, Hg2+ displayed a stronger toxicity at 12 - 24 h stress, while Cd2+ was at 0 - 12 h stress. It seemed that seed coat played an important role in seed tolerance to heavy metals. The interaction between non-toxic ions and heavy metal ions on seed germination showed that Ca2+, Mg2+, K+ and Na+ at 5 mmol x L(-1) could enhance the toxicity of Hg2+, but did not affect Cd2+ toxicity. For seedling growth, Ca2+, Mg2+, K+ and Na+ might enhance the toxicity of Hg2+, Ca2+ might alleviate the toxicity of Cd2+ but enhance the toxicity of Cu2+ , and K+ might alleviate Pb2+ toxicity. The mechanism of heavy metals injury was discussed in the paper.