Effect of Heavy-Metal Toxicity on the Cation-Exchange Capacity of Plant Roots

The cation-exchange capacity of the roots of 5 plant species suffering from heavy metal toxicity has been measured. For the crops studied, excess Ni, Co, and Zn produce an increase, and Mn a reduction in the cation exchange capacity. Excess Cu produced an increase in root exchange in the case of oats and sunflower, and a reduction in the case of tomato, pea, and bean. The heavy metals produced an increase in Ca absorption in oat and tomato, and reduced Ca absorption in peas. The visual symptoms of chlorosis and necrosis seen in plants suffering from heavy-metal toxicity are a reflection of their disturbed metabolism. 20 references, 1 figure, 6 tables.