Yield and metal composition of brinjal (Solanum melongena) and pigweed (Amaranthus tricolor) as influenced by lead contaminated soils

Abstract

Leafy vegetables are known to accumulate large amounts of heavy metals in their shoots and roots because of their high biomass and root proliferation. In a pot culture experiment, a sandy loam soil was polluted with lead (Pb) at 0, 5, 10, 20, 40, 60, 80, 120, 160, 320 and 640 mg kg-1 soil to asses the accumulation pattern and its effect on dry matter yield and mineral composition in brinjal and pig-weed. There was a decrease in dry matter yield due to phytotoxic effect of Pb as a result of its application. The rate of Pb application, at which significant decline in dry matter yield of root and shoot occurred, varied depending on the vegetable. It was 120 and 80 mg Pb kg ' soil in both roots and shoots for pig-weed and brinjal respectively. Both pig-weed and brinjal exhibited toxicity symptoms of Pb in the form of interveinal chlorosis with necrosis and scorching at the margin of the leaves in treatments receiving 160 mg Pb kg-1 and above. The reduction in root and shoot growth was in agreement with the amounts of extractable Pb in the soils. The total content of Pb in crops increased gradually with graded rates of applied Pb and roots accumulated much higher amount than shoot. The relationship of Pb with Zn and Mn was antagonistic in both roots and shoots while in case of Fe, it was synergistic in roots and antagonistic in shoots for both crops. The relationship of Cu with Pb was very weak