Effect of Cr~(6+) Stress on Seedling Root Growth and Cell Division of Vicia faba

In order to elucidate the genetic toxicity of chromium(Cr6+) stress for root tip cells of V.faba,the experiment was conducted to investigate the effects of Cr6+ on seed germination,seedling root growth,root tip cell division and chromosomal aberration.The results indicated that the seed germination rate of V.faba was increased under lower Cr6+ mass concentrations.However,the seed germination were restrained at higher Cr6+concentration,and the feasible Cr6+ mass concentrations was decreased with the treatment duration prolonged.The root growth was obviously inhibited when the Cr6+ mass concentration was above 10 mg/L,and the connection between time and effect could be observed.The obvious morphological changes were found under higher Cr6+ mass concentrations: the twisted roots,brown,black brown,even black spots in root tips and partially hardened roots.With the Cr6+ mass concentration(≥5 mg/L) increased and the treatment duration prolonged,the mitotic index of root tip cell was decreased,and there was obviously time-effect connection between doses and effect.The proportion of mitotic metaphase cells was relatively increased,while decreasing those of prophase,anaphase and telaphase cells in root tips of V.faba.Cr6+ stress could induce the occurrence of structural chromosomal aberrations,including chromosomal breakage,chromosomal bridge,laggard chromosome,chromosomal stickiness and multipolar division,but the highest number of chromosomal breakage was observed,the second micronucleus.Micronucleus frequency increased with the increase of Cr6+ concentration and the prolong of treatment duration when the Cr6+ mass concentration≤100 mg/L,however,micronucleus frequency decreased at 200 mg/L Cr6+for 48 h.