Abstract
To examine the effect of kinetin (Kin) in alleviating the toxic effects of lead (Pb) and chromium (Cr) on four black
gram cultivars this study was conducted in earthen pots lined with polyethylene bags and filled in with sterilized
sand, at the University of Agriculture, Faisalabad, Pakistan during the spring season 2004. Thirty days after
germination we imposed six treatments viz. control (T0), Pb @ 20 mg kg-1 (T1), Cr @ 30 mg kg-1 (T2), Kin @ 100
µg/g (T3), Pb @ 20 mg kg-1 & Kin &100 µg/g (T4), Cr @ 30 mg kg-1 & Kin @100 µg/g (T5). We observed significant
reduction in the stomatal conductance, assimilation rate, transpiration rate, leaf area, and harvest index of black
gram plants treated with Pb and Cr singly. The joint application of Kin and heavy metals (Pb and Cr) showed
significant improvement in all the parameters under investigation but it could not fully ameliorate the toxic effects
of heavy metals. As regards the heavy metal ion uptake by different plant organs, plants treated with Pb and Cr
alone showed higher sequestering of both metals in their roots. However, plants receiving joint application of Kin
and heavy metals (Pb and Cr) showed higher translocation of both heavy metals towards their shoot. Cr
particularly showed more translocation towards roots than Pb. Despite both heavy metals significantly reduced all
the parameters, Pb application either alone or in combination with Kin proved more toxic. All the parameters
showed highly significant negative correlation with Pb content in both roots and shoot. The Cr content in the roots
of black gram plants also showed strong negative correlation with all these parameters. Among the black gram
cultivars Mash ES1 (V4) proved comparatively more sensitive, Mash 80 (V1) showed more resistance, while Mash
88 (V2) and Mash 97 (V3) exhibited optimum sensitivity to heavy metal treatments. This study has great
implication for the selection of black gram cultivars suitable for cultivation in the riverine areas of Pakistan and
resembling agro-ecosystems in the world threatened with the drainage of untreated industrial effluents.
