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- Assessing of tolerance to metallic and saline stresses in the halophyte Suaeda fruticosa: The indicator role of antioxidative enzymesPublication . Bankaji, Insaf; Caçador, Isabel; Sleimi, NoomeneMany areas are simultaneously affected by high concentrations of salts and trace metal elements (TME), the latter constituting a serious threat to human health. In the present study, we determined the combined effect of high salinity and toxic levels of trace elements on physiological behavior of the halophytic species Suaeda fruticosa. Plants were cultivated for three months with an irrigation solution supplemented separately with different concentrations of Pb2+ and Zn2+ (0, 200, 400 and 600 microM) with and without 200 mM NaCl. Growth, total chlorophyll, water status and ion nutrition were quantified and antioxidant enzyme activities [ascorbate peroxidase (APX), guaiacol peroxidase (GPX), and catalase (CAT)] were studied. Our results revealed that S. fruticosa has a strong ability to tolerate lead and zinc. This halophyte accumulated higher concentrations of TME in their roots. Growth parameters of S. fruticosa were not significantly affected by TME. An enhancement of Ca2+ concentration accompanied by a decrease of Mg2+ content was observed under Pb2+ or Zn2+ treatments whereas K+ content was not affected by TME. Of the antioxidant enzymes, the activity of CAT and APX was increased by metal stress. However, the activity of GPX was diminished by increasing TME concentrations. It was concluded that NaCl 200 mM had a positive impact on the response of S. fruticosa to Zn2+ toxicity, acting through a decrease in Zn absorption.
- Accumulation potential of Atriplex halimus to zinc and lead combined with NaCl: Effects on physiological parameters and antioxidant enzymes activitiesPublication . Bankaji, I.; Pérez-Clemente, R.M.; Caçador, Isabel; Sleimi, N.An experiment in this study was designed to investigate the effect of different concentrations of Zn2+ or Pb2+ (0, 200, 400 and 600 μM) with NaCl (0, 200 mM), on the morphological and physiological parameters as well as the antioxidative response of the halophytic species Atriplex halimus. Results showed that Pb2+ had no significant impact on biomass production while Zn2+ significantly affected plant development mainly at high concentration, 600 μM. Total chlorophyll content did not change significantly under elevation concentrations of Zn2+ when compared to control. However, there was a modest decrease in total chlorophyll concentration in the leaves of A. halimus grown in a medium supplemented with 600 μMPb2+ and with combined stress Pb2+/NaCl. Zn2+ and Pb2+ contents in tissues were higher in the belowground organs of this halophyte. Overall results pointed out that application of different concentrations of Zn2+ or Pb2+ disturbed status of nutrients in A. halimus. Analysis of antioxidant enzymes [ascorbate peroxidase (APX), guaiacol peroxidase (GPX), and catalase (CAT)] showed that the activity was diminished by increasing Zn2+ concentrations in the medium. Whereas, the addition of Pb2+ in the medium increased CAT activity and decreased APX activity.
- Physiological and biochemical responses of Suaeda fruticosa to cadmium and copper stresses: growth, nutrient uptake, antioxidant enzymes, phytochelatin, and glutathione levelsPublication . Bankaji, I.; Caçador, Isabel; Sleimi, N.Environmental pollution by trace metal elements (TMEs) is a serious problem worldwide, increasing in parallel with the development of human technology. The present research aimed to examine the response of halophytic species Suaeda fruticosa to oxidative stress posed by combined abiotic stresses. Plants have been grown for 1 month with an irrigation solution supplemented with 200 mM NaCl and 400 μM Cd2+ or 400 μM Cu2+. The level of glutathione (GSH), phytochelatins (PCs), and antioxidant enzyme activities [ascorbate peroxidase (APX), guaiacol peroxidase (GPX), and catalase (CAT)] as well as lipid peroxidation was studied to see the stress exerted by the TME and the level of tolerance and detoxification strategy adopted by S. fruticosa. Relative growth rate (RGR) decreased under Cd2+ stress in this species, whereas Cu2+ did not have any impact on S. fruticosa performance. Cd2+ or Cu2+ enhanced malondialdehyde, suggesting reactive oxygen species-induced disruption of membrane integrity and oxidative stress in S. fruticosa. On the other hand, the activities of the antioxidant enzymes CAT, APX, and GPX diminished and mineral nutrition was disturbed by metal stress. S. fruticosa was able to synthesize PCs in response to TME toxicity. However, data indicate that GSH levels underwent a significant decrease in roots and leaves of S. fruticosa stressed by Cd2+ or Cu2+. The GSH depletion accompanied by the increase of phytochelatin concentration suggests the involvement of GSH in the synthesis of phytochelatins.