Obtaining Large Numbers of Metaphases in Barley Root Tips

This technic was developed primarily to facilitate the scoring of radiation-induced chromosome aberrations in the first mitotic root-tip division of Hordeum vulgare (barley). The two main features of the technic are (1) the germination of the barley seeds in 0.2% colchicine, which destroys the spindle and thus causes the accumulation of large numbers of cells in metaphase, and (2) the digestion of the middle lamella by treatment with 4-5% pectinase, which allows the cells to be separated from one another and to be flattened. It was found also that the use of hot (60°C) Carnoy's fixative both shortened the time necessary for good fixation and removed any droplets of lipid in the cells that might otherwise obscure the chromosomes.