Effects of Zn2+ on root growth,cell division, and nucleoli of Allium cepa L.

The effects of different concentrations of Zn²⁺ion on root growth,cell division,and nucleoli of Allium cepa were studied. The test Zn²⁺ ion concentration was made up from zinc sulphate (ZnSO₄. 7H₂O) ranging from 10^-7 to 10^-2 mol/L. The solutions were prepared in tap water (pH =6. 5).The results indicated that Zn²⁺ could obviously inhibit root growth at concentrations from 10^-4)to 10^-2 mol/L.Roots treated with zinc sulphate showed the presence of c-mitosis, anaphase bridges,including sticky and fluidized bridges (at 10^-3 to 10^-2 mol/L) , chromosome stickiness, irregularly shaped nuclei, broken nuclei and micronuclei. A toxicity effect was also observed on the nucleoli using silver staining technique after 48h of treatment with 10^-4to 10^-2 mol/L Zn²⁺, e. g,the nucleolar particulate material scattered around the nucleoli in the nucleus of root tip cells.