Oxidative stress and antioxidant defense mechanism in mung bean seedlings after lead and cadmium treatments

This research was an attempt to study the effect of heavy metals lead and cadmium (0.05 mM and 0.3 mM) on growth and antioxidant enzymes of seedlings of 2 mung bean genotypes (NM 19-19 and Azri mung-2006). Results revealed that germination percentage and seedling length decreased when compared with the control for both genotypes. However, seedling length and germination percentage was better in NM 19-19 as compared to Azri mung-2006. Elevated levels of protein were observed under metal stress in both genotypes. Heavy metals induced oxidative stress in plants, causing membrane injury as observed by enhanced level of malondialdehyde (MDA) contents. Increase in antioxidant enzymes activity was detected for guaiacol peroxidase (GPX) and catalase (CAT). However, ascorbate (APX) activity decreased under stress for both genotypes. We observed more MDA content and GPX and APX activity in Azri mung-2006 as compared to NM 19-19 when high concentrations of Pb and Cd were added. This revealed that NM 19-19 was tolerant whereas Azri mung-2006 was sensitive to Pb and Cd. It was further noticed that Cd imposed a more deleterious effect than Pb on both genotypes.