Copper-induced alterations in structure and proliferation of maize root meristem cells

Maize plants (Zea mays L., cv. Kneja 21, 611) were treated with various copper concentrations to investigate the effect of high copper concentrations on root growth, cell proliferation and morphology of meristem root cells. Electron microscopy and light microscopic autoradiography were used to study the influence of the copper excess on these parameters. The higher concentrations of copper inhibited root growth, shortening root length and decreasing fresh and dry root weight. Treatments with the copper excess led to a decrease in the number of labelled meristem cells after H-3-thymidine administration. The strongest inhibition was achieved by 78 mu mol/L copper when only 6 % of the nuclei were in the S-phase of the cell cycle compared with 47 % in. the control cells. These data show that copper interrupts the progression of nuclei at the crucial G(1)/S transition point of the cell cycle, when it prevents their entry into mitosis. The decreased root growth could be due to the effect of copper on root meristem cell proliferation. Ultrastructural investigation of root meristem cells in the case of copper excess (31-78 mu mol/L) showed disturbance of plasmalemma, endoplasmic reticulum and mitochondrial membranes.