Alleviation of cadmium-induced genotoxicity and cytotoxicity by calcium chloride in faba bean (Vicia faba L. var. minor) roots

Abstract

Alleviation of cadmium-induced root genotoxicity and cytotoxicity by calcium chloride (CaCl₂) in faba bean (Vicia faba L. var. minor) seedlings were studied. Faba bean seeds were treated with H₂O or 2% CaCl₂ for 6 h before germination. Seeds were then exposed to 0 and 50 µM CdCl₂ concentrations for 7 days. Genotoxic damaging effects of Cd was examined through the determination of the mitotic index (MI), chromosomal aberrations (CA) and micronucleus (MN) in the meristem cells of faba bean roots. Similarly, effects of Cd stress on metal accumulation, total membrane lipid contents, total fatty acid composition (TFA), lipid peroxidation as indicated by malondialdehyde production, soluble protein and non-protein thiols (NP-SH) contents, hydrogen peroxide production and the activities of superoxide dismutase (SOD), catalase (CAT) and guaiacol peroxidase (GPX) were evaluated after 7 days of Cd stress in the seedling roots. Cd stress resulted in the reduction of MI, in addition to MN formation and CA induction in the roots of non-primed seeds (treated with H₂O). Moreover, Cd induced lipid peroxidation, H₂O₂ overproduction and loss of membrane lipid amount and soluble protein content, and changes in the TFA composition in roots of faba bean seedlings. SOD activity declined, but CAT and GPX activities increased. However, seed pre-treatment with CaCl₂ attenuated the genotoxic and cytotoxic effects of Cd on Vicia faba roots. The results showed that CaCl₂ induced reduction of Cd accumulation, improved cell membrane stability and increased the antioxidant defence systems, thus reducing and alleviating Cd genotoxicity and oxidative damage.

Keywords: Cadmium; Genotoxicity; Membrane lipid; Oxidative stress; Roots; Seed priming.

Fig. 1

Cadmium effect on germination rate (a), root length (b), root fresh weight (c) and soluble protein content (d) in roots of faba bean seedlings, pretreated with 2% CaCl₂ (P) or H₂O (NP) for 6 h, and germinated for 7 days under 0 or 50 µM Cd. Values are the means of at least 12 replications ± SE. The data followed by different letters are significantly different at P ≤ 0.05

Fig. 2

Representative mitotic abnormalities in apical meristem cells of faba bean Cd-treated roots. a micronuclei in interphase; b sticky telophase; c, d chromosome bridges in anaphase; e disoriented chromosomes at metaphase; f fragmented chromosomes at anaphase; g binucleate cell; h multipolar anaphase; i metaphase with chromosome fragments. Bar = 50 µm

Fig. 3

Histochemical detection (a) and accumulation of H₂O₂ (b) and MDA content (c) in roots of faba bean seedlings, pretreated with 2% CaCl₂ (P) or with H₂O (NP) for 6 h, and germinated for 7 days under 0 or 50 µM Cd. Values are the means of at least 10 replications ± SE. The data followed by different letters are significantly different at P ≤ 0.05

Fig. 4

Total membrane lipid (TL) content in roots of faba bean seedlings, pretreated with 2% CaCl₂ (P) or with H₂O (NP) for 6 h, and germinated for 7 days under 0 or 50 µM Cd. Values are the means of six replications ± SE. The data followed by different letters are significantly different at P ≤ 0.05

Fig. 5

Cadmium effects on SOD (a), CAT (b), GPX (c) activities and non-protein thiols (NP-SH) content (d) in roots of faba bean seedlings, pre-treated with 2% CaCl₂ (P) or with H₂O (NP) for 6 h, and germinated for 7 days under 0 or 50 µM Cd. Values are the means of at least six replications ± SE. The data followed by different letters are significantly different at P ≤ 0.05