Effect of Increasing Concentrations of Lead and Cadmium on Cucumber Seedlings

The effect of lead and cadmium on biomass accumulation of cucumber seedlings (Cucumis sativus L.) as well as the contents of abscisic acid (ABA), free proline and soluble proteins in leaves were studied. Seedlings were subjected to lead nitrate or cadmium bromide in low concentrations (1 - 5 µM) for 1, 4 or 7 d, and then to the action of the same substances in high concentrations (500 - 1000 µM). The pretreatments of the seedlings with heavy metals in low concentrations enabled them to tolerate the subsequent high concentrations of cadmium and lead without injury. The plant responses to heavy metal treatment were accompanied by the accumulation of ABA, free proline and soluble proteins in leaf tissues.