Oxidative stress biomarkers and metabolic changes associated with cadmium stress in hyacinth bean (Lablab Purpureus)

Cadmium (Cd)-induced stress in hyacinth bean (Lablab purpureus) was investigated by growing seedlings in a nutrient solution containing increasing cadmium concentrations (0 to 50 μM), under strictly controlled growth conditions. Changes consequent to Cd uptake in growth parameters, enzyme activities and other stress response factors directly or indirectly are related to the cellular free radical scavenging systems. Antioxidants and other stress response components were studied in roots and leaves of 10-day old seedlings over 72 h of exposure. A significant decrease in length, relative water content (RWC), weight of shoot and root, and chlorophyll content was observed in seedlings growing on >10 μM CdCl2. Oxidative stress markers, H2O2, malondialdehyde, proline and total soluble sugars were elevated in both leaves and roots. Ascorbate and phenol contents increased in leaves, but, decreased in roots. Reduced glutathione levels declined in both tissues. Cd stress enhanced antioxidant enzymes, guaiacol peroxidase, glutathione reductase, ascorbate peroxidase and polyphenol oxidase in concentration and time dependent manner in leaves. Antioxidant enzymes in roots showed inverse relationship with concentration and time of exposure. Catalase activity was found to decrease in both leaves and roots. Metabolic enzymes β-amylase and acid phosphatase activity increased in both leaves and roots. The results suggest that primary antioxidative response originates from leaves of Hyacinth bean even though roots are involved in direct uptake of heavy metals. The root tends to accumulate Cd and thus excludes its uptake by leaves.Keywords: Antioxidants, antioxidant enzymes, cadmium, Hyacinth bean.African Journal of Biotechnology Vol. 12(29), pp. 4670-468