PHYSIOLOGICAL AND BIOCHEMICAL RESPONSES IN MEDITERRANEAN SALTBUSH ( ATRIPLEX HALIMUS L., AMARANTHACEAE JUSS.) TO HEAVY METAL POLLUTION IN ARID ENVIRONMENT

Environmental pollution as induced by mining activities is increasingly become a problem with a great concern in many developing countries around the world. This paper reports the finding of a study undertaken to investigate the physiological and biochemical effects of heavy metals. Futhermore, we evaluate the effects of Zinc (Zn), Lead (Pb), Copper (Cu), Iron (Fe), and Cadmium (Cd), on Mediterranean saltbush (Atriplex halimus L., Amaranthaceae Juss.) grown in Arid zone from Southern Tunisia. The research is conducted at 5 different sites, located at different distant populations from the Tunisian Chemical Complex (TCC) situated in Gabes. Our results showed that leaves of A. halimus were enriched following decreasing order: Cu, Zn, Pb, and Fe compared to root samples. However, and for Cd, an opposite pattern was observed and leaves showed lower mean concentration. The Bioconcentration Factor (BCF) is used to meaure the heavy metal accumulation efficiency in the plant. For Cu, and for the 5 studied sites, BCF values >1 indicate that A. halimus is a potential heavy metal hyperaccumulator species. Regarding physiological status of the plant, heavy metals affected the different parameters of A. halimus including relative water content, chlorophyll level, lipid peroxidation and the production of hydrogen peroxide (H2O2). Oxidative stress as induced by heavy metal initiate several biochemical responses and mechanisms in A. halimus and lead to the accumulation of osmolytes and the activation of both enzymatic and non -enzymatic antioxidant systems. The concentration of heavy metals in plant tissues seem to be proportional with the magnitude of physiological and biochemical processes.