Sensitivity of Allium cepa and Vicia faba towards cadmium toxicity

Sensitivity of common onion (Allium cepa L.) and faba bean (Vicia faba L.) to cadmium (Cd) stress was investigated using genotoxicity endpoints. Simultaneously, the antioxidative stress enzymes (guaiacol peroxidise and catalase) and lipid peroxidation [malonaldehyde (MDA) content] were investigated in the plants exposed to Cd in solution. The endpoints screened for genotoxicity included chromosomal aberrations, micronuclei frequency and mitotic frequency. Additionally comet assay was performed for DNA fragmentation. Evan’s blue uptake by the root meristems as a cell death parameter served as indicator of cytotoxicity. The results indicated that exposure to Cd induced dose-dependent increase in chromosomal aberrations, DNA fragmentation and micronucleus frequency in both A.cepa and V. faba. The enzymes guaiacol peroxidase (GPX) and catalase (CAT) activities increased in both the plants and were higher in V. faba. A positive correlation between the activity of GPX and CAT and MDA content was recorded at all concentrations of Cd. Regarding sensitivity, our results showed that V. faba is more sensitive plant than A. cepa towards Cd –induced toxicity. Higher genotoxicity level correlated to the increased level of oxidative stress in root tissues. This was likely to be an important cause of Vicia plant to be less tolerant than Allium.