Physiological, biochemical and molecular responses of common bean (Phaseolus vulgaris L.) plants to heavy metals stress

Abstract

Heavy metals are essential and important for plants growth, and play as key components of many vital compounds. However, when they increase in concentration, heavy metals show symptoms such as growth delay and inhibition of biochemical reactions. The current study focused on the impact of five heavy metals (lead, chromium, nickel, cadmium, zinc) on growth and performance of common bean (Phaseolus vulgaris L. cv. Nebraska) plants before and after liming (CaCO₃ + MgCO₃) as soil correction treatment for the sake of remediation for heavy metal pollution in soil. Chemical analysis of carbohydrates showed significant increases in the contents of reducing sugars in response to lead, cadmium and nickel stress, which were decreased by liming treatments. The contents of total soluble sugars also increased in all heavy metal-treated plants but zinc. All heavy metals significantly lowered the leaf contents of the photosynthetic pigments (chlorophyll a, chlorophyll b and carotenoids). The sodium dodecyl sulphate polyacrylamide gel electrophoreseis (SDS-PAGE) of proteins indicated variations in the profile of electrophoretic protein bands in heavy metal-stressed common bean plants before and after liming. The results indicate that the investigated heavy metals were absorbed from the soil solution and then accumulated in the tissues of common bean plants in variable concentrations. The highest accumulation were lead (Pb) and chromium (Cr) then cadmium (Cd), zinc (Zn) and nickel (Ni) while the magnitude of limiting the retarding rate of absorption and accumulation was: Pb > Ni > Cr > Zn > Cd, respectively.

Keywords: Heavy metals, common bean, liming, chlorophyll.

African Journal of Biotechnology Vol. 12(29), pp. 4614-4622