Increasing nuclear ploidy enhances the capability of antioxidant defense and reduces chromotoxicity in Lathyrus sativus roots under cadmium stress

Abstract

The modulation of antioxidant defense and cytogenetic parameters was studied in Lathyrus sativus L. roots at 3 different ploidies under a control treatment (0 µM) and 5, 10, 25, and 50 µM of CdCl2 in nutrient media. Root growth was inhibited in diploids from 10 µM and in triploid from 25 µM. Growth was normal in tetraploid roots. Although Cd accumulated in ascending order of ploidy, perturbation of antioxidant defense was the severest in diploid, moderate in triploids, and not observed in tetraploid roots even at 50 µM. Low antioxidant enzyme activities led to overaccumulation of H2O2, consequently resulting in oxidative damage through membrane lipid peroxidation in treated diploid roots. Cd-induced chromotoxicity was exhibited by low mitotic fidelity in diploid chromosomes and to some extent in triploids. DNA base-specific fluorescent chromosome banding revealed GC to AT transition and even perturbation of the GC-rich region in the nucleolar organizing chromosome in diploid, presumably facilitating chromosome breakage at a lower ploidy level due to Cd treatment. By contrast, the normal to enhanced GC region was associated with a low percentage of chromosome breakage and other anomalies at higher ploidies exposed to Cd. Results suggest better tolerance of grass pea genotypes to Cd at elevated ploidy levels.