Effects of cadmium and lead on radish plants with particular reference to movement of metals through soil profile and plant

Summary

Studies were made of the effects of insoluble and soluble compounds of Cd and Pb on the growth of radish plants. The effect of Cd toxicity was progressive chlorosis, particularly of the young leaves, followed by necrosis. The effect of Pb toxicity was stunted growth. Root growth was more inhibited than shoot growth in metal-contaminated soils. On a molarity basis Cd was twenty times more toxic than Pb.

A microcosm study involving soil columns showed that Cd and Pb are largely retained within the surface soil. There was very little movement of these metals, particularly of Pb, through the sub-soil horizon. The addition of Cd or Pb to the soils in columns raised the levels of these metals in the plant tissue to phytotoxic concentrations and reduced the growth considerably. Such phytotoxicity seemed to be associated with some reduction of Zn in the plant tissue to near the lower critical level of deficiency threshold value. Of the two metals studied Cd was more concentrated in the plant shoot and Pb in the plant root. Considering this and also the chemical forms of the metals in the soil profile, the mobility of Cd was found to be higher than Pb within the soil-plant system studied.