Abstract: The effects of cadmium chloride solution of different concentrations (10-7~10-2 mol/L) on root growth ultrastructural alterations in root tip cells of garlic (Allium sativum L.) were studied. The results showed that with the increase of Cd²⁺ concentration or treatment time, the rate of root growth decreased successively or stopped. The major change was that the higher concentration of cadmium (10-3mol/L) exhibits unusual deposition of electron dense globules in the root cells. These globules whose electron density was greater outside than inside were big or small, and were distributed nearby vacuoles in the cytoplasm. The nucleoplasm in most of nuclei was highly condensed. The other toxic effects that were observed in treated cells included formation of plasmolysis, disintegration of cell organelles and increase in vacuolation. The results from X-ray microanalysis showed that there were no cadmium ions in these globules. The results from scanning electron microscope indicated that the epidermal cells of the root tips treated with higher concentration of Cd²⁺(10-2 mol/L) appeared more hardened; the cell walls obviously increased in thickness and many mucilage exudates were deposited in the cell walls.

Key words: Allium sativum L., Cadmium chloride, Root tip cells, Ultrastructure, X-microanalysis