Antioxidant defense strategies of urban ornamental plants in southern Iran against heavy metals

Abstract

One of the effective approaches to reduce heavy metals (HMs) contamination is phytoremediation. The concentration of 10 HMs was measured in 10 ornamental plants grown in the city of Bushehr, located in southern Iran. The concentration of HMs was determined by ICP-MS. Some physiological parameters and antioxidant enzymes activity were measured. Bougainvillea had greater amount of Zn (61.86 mg/kg D.W.), Cu (45.52 mg/kg D.W.), and Cr (14.71 mg/kg D.W.) than the other HMs. Greatest amount of Co (0.686 mg/kg D.W.), Fe (428.00 mg/kg D.W.), and Ni (6.44 mg/kg D.W.) was obtained in Conocarpus erectus. Also, Clerodendrom inerme had maximum As (0.0087 mg/kg D.W.) and Sn (2.516 mg/kg D.W.). The POD activity (1.462 and 1.214 U/g F.W./min) was highest in leaves of C. inerme and Ficus elastica containing the highest concentrations of As, Sn, and Pb, respectively. The SOD activity was high in these two species. Synthesis of osmolytes increased under Co and Sn stresses. The selected plant species followed a defensive strategy (enzymatic or non-enzymatic) against excess of HMs. Overall, shrubs were much more suitable than trees for absorption and accumulation of HMs, and C. inerme, F. elastica, and Bougainvillea are the best plant species for phytoremediation.