胁迫时间与非毒性离子对重金属抑制拟南芥种子发芽及幼苗生长的影响

测定了Hg²⁺ 、Cd²⁺ 、Cu²⁺ 、Pb²⁺单一重金属胁迫对拟南芥种子发芽和幼苗生长的影响.结果表明，重金属对幼苗生长的毒性大于对种子发芽的毒性，以抑制种子发芽的IC50为指标，4种重金属的毒性顺序为Hg²⁺>Cd²⁺>Pb²⁺/Cu²⁺，以幼苗生长为指标，则毒性顺序为：Cu²⁺>Hg²⁺>Cd²⁺/Pb²⁺，并随着胁迫时间延长，种子萌发率下降.此外，不同重金属在不同发芽时段对种子的毒性也不尽相同，Cd²⁺的毒性在种子吸水后的0～12 h 大于12～24 h, 而Hg²⁺毒性在12～24 h大于0～12 h，其中，种皮对减轻重金属毒性起着十分重要的作用.通过非毒性离子(Ca ²⁺ 、Mg ²⁺ 、K ⁺ 、Na ⁺ )与重金属离子(Hg²⁺、Cd²⁺ Cu²⁺、Pb²⁺)交互作用对拟南芥种子发芽及幼苗生长效应的研究发现，5 mmol·L^-1的Ca ²⁺ 、Mg ²⁺ 、K ⁺ 、Na ⁺可以增强Hg²⁺对种子发芽的毒性，但对Cd ²⁺的毒性却没有影响.对于幼苗来说，Ca ²⁺ 、Mg ²⁺ 、K ⁺ 、Na ⁺可以显著增强Hg²⁺的毒性，Ca ²⁺可以缓解Cd²⁺的毒性，但却增加Cu ²⁺的毒性，K⁺可以缓解Pb ²⁺对幼苗的毒害作用.最后，本文对重金属的毒害机理进行了探讨.

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.