Lead phytotoxicity induced damages in growth and metabolism of cabbage

Cabbage (Brassica oleracea cv. capitata) var. Pride of India plants were grown in refined sand till maturity at excess levels of lead viz., nil (Control), 0.1, 0.2, 0.4, 0.5 and 1.0 mM applied as lead nitrate. Excess Pb (>0.1 mM Pb) depressed the growth, young leaves developed interveinal chlorosis along the margins, gradually chlorosis intensified and leaves became thick and size of the head reduced markedly. The symptoms were marked in plants grown at 1.0 mM Pb. The symptoms of excess Pb were discernible late in other treatments from 0.1 to 0.5 mM Pb and the intensity was low. In cabbage, excess Pb significantly reduced the biomass, concentration of iron in different parts, chlorophylls, Hill reaction activity and increased the lead concentration and specific activity of catalase, peroxidase, acid phosphatase and ribonuclease in leaves. The values of threshold of toxicity and toxicity of Pb were 119 and 138 μg g⁻¹ dry matter respectively in young leaves of cabbage.