The effect of Pb and Ni on chlorophyll a, b, carotenoids and proline content of Black gram (Vigna mungo L.) seedlings were evaluated under 10, 50 and 100 µM concentration. These concentrations significantly affected chlorophyll, carotenoid and proline content of Black gram as compared to control. Pb and Ni at 10 µM concentration resulted in less significant effect on chlorophyll, a, b and carotenoids. Carotenoids were less affected compared to Chl a and b, while higher concentrations (50 and 100 µM) significantly reduced chlorophyll and carotenoid contents of the seedlings. However, the addition of nitrogen (5 mM) somehow minimized the effect of these heavy metals. Nitrogen increased the chlorophyll content of metal treated plants. The proline content of plants was increased under Pb and Ni treatments (10, 50 and 100 µM). In this case, the additional supply of nitrogen in the form of ammonium nitrate decreased proline content of plants treated with Pb and Ni.
Key words: Carotenoid, chlorophyll, lead, nickel, proline, Vigna mungo.
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