Studies on phyto-genotoxic assessment of tannery effluent and chromium on Allium cepa

Tannery effluent contributes significantly to pollution of the environment. In this study, phytotoxic and genotoxic effects of tannery effluent and chromium (Cr) were investigated in Allium cepa. Forthis purpose, tannery effluent was collected from "Up flow Anaerobic Sludge Blanket" (U.A.S.B) Jajmau, Kanpur. A. cepa were exposed to various concentrations of tannery effluent (0.0, 3.125, 6.25, 12.50, 25.0%) and Cr (0.0, 1.0, 2.0, 4.0, 8.0 mgl(-1)) for 48 and 168 hr. The perusal of data revealed that the physico-chemical characteristics of tannery effluent viz. pH (8.5), EC (11.94 dSm(-1)), BOD (499 mgl(-1)), COD (1382 mgl(-1)) and Cr content (2.32 mgI(-1)) were much higher than the prescribed permissible limit for industrial effluent discharged into inland waters. These substances provoked phytotoxic and genotoxic effects in A. cepa. Total chlorophyll and protein content in leaves of tannery effluent and Cr treated plants decreased significantly in dose-duration dependent manner. A maximum decrease of 86.29 and 84.26% in total chlorophyll and 81.27 and 76.16% in protein content was observed after 168 hr of exposure while carotenoid content increased up to 6.25% effluent and 2.0 mgl(-1) Cr treatment and decreased further. In all treated plants, a significant (p > or = 0.05) reduction in root length, mitotic index (MI) and induction in chromosomal (CA)/mitotic (MA) aberration and micronuclei (MNC) were observed as compared to unstressed plants. A maximum reduction of 81.15 and 79.71% in MI, and induction of 6.8 and 4.8% in CA, 29.24 and 26.66% in MA and 0.52 and 0.43% in MNC were found at 12.50% effluent and 4 mgl(-1) Cr treated plants as compared to unstressed plants, however at highest effluent and Cr concentration both the plants showed pyknosis condition after 168 hr.