Cadmium Stress in Halophyte Thellungiella halophila: Consequences on Growth, Cadmium Accumulation, Reactive Oxygen Species and Antioxidative Systems

Abstract

Cadmium (Cd) stress on the growth and antioxidant system of the halophyte Thellungiella halophila is studied to explore heavy metal tolerance and the role of antioxidants in Cd tolerance. Biomass production of both leaves and roots of four leaves T. halophila seedlings significantly decreased under 0, 0.3, 0.6, and 0.9 mmol L-1 CdCl2 for 14 days compare to no-Cd control. Meanwhile, the photosynthetic oxygen evolution rate significantly decreased and the chlorophyll content slightly decreased. The MDA and hydrogen peroxide (H2O2) contents of leaves increased as the Cd concentrations increased, and the oxidative damage in Cd-treated seedlings was greater under Cd stress than under the no-Cd controls. Though the translocation factor (TF) was always under 1, T. halophila can tolerate and accumulate more than 100 mg kg-1 Cd in shoot dry biomass. T. halophila mitigated the oxidative damage by increasing enzymatic components, glutathione (GSH), and ascorbic acid (AsA). In Cd-treated seedlings, both the leaf GSH and AsA and the activities of both peroxidase (POD) and catalase (CAT) were significantly greater under Cd stress than under no-Cd control. No significant differences were found in the activity of ascorbate peroxidase (APX), glutathione reductase (GR) and superoxide dismutase (SOD). These results critically summarize the effects of Cd stress in T. halophila and these results above indicate that the antioxidants are responsible for Cd tolerance in T. halophila.