Assessment of Hexavalent Chromium Accumulation of Beta Vulgaris L. Var. Cicla and the Change of Its Antibacterial Activity

Abstract

ABSTRACT Hexavalent chromium (Cr(VI)) is a frequently encountered heavy metal contaminant in agricultural soil and water sources resulting from industrial and agricultural applications, traffic, and urbanization. It is the most toxic form of chromium (Cr), which causes severe health problems. The accumulation capacity of Swiss chard (Beta vulgaris L. var. cicla) for hexavalent chromium and the effect of heavy metal accumulation on the antibacterial activity of plant extracts were evaluated in a pot experiment. The soil was treated with 10 mg kg−1 hexavalent chromium, 30 days prior to planting Swiss chard seedlings. After the harvest, macro- and micronutrient elements and Cr were measured using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-OES). Moreover, plant extracts were obtained by maceration in methanol and the extracts were tested against Gram-positive and Gram-negative bacteria. Cr was found to be uptaken and accumulated with a high concentration (54.7 ± 0.23 mg kg−1) in the aerial parts (transfer factor = 74.95). Cr toxicity reduced plant development and the macronutrient elements phosphorus and potassium in Swiss chard. The micronutrient elements iron and boron were found to be significantly increased in plant upon chromium in a synergistic manner with Cr. Additionally, the antibacterial activity of the extract of Swiss chard decreased against Staphylococcus aureus and Enterococcus faecalis around 50%. Moreover, the number of culturable bacteria decreased about 40% in soil after chromium treatment. The results suggested that this plant can accumulate a high amount of Cr in its aerial parts, which may decrease the health effects of the extracts.