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Morpho-physiological and biochemical responses of Arabidopsis thaliana (accession N1438) to bicarbonate-induced iron deficiency were investigated. Plants were grown in cabinet under controlled conditions, in a nutrient solution containing 5 lM Fe, added or not with 10 mM NaHCO 3 . After 30 days, bicarbonate-treated plants displayed significantly lower biomass, leaf number and leaf surface area as compared to control plants, and slight yellowing of their younger leaves was observed. Potassium (K ? ) content was not modified by bicarbonate treatment in roots, whereas it was significantly diminished in shoots. Their content in ferrous iron (Fe 2? ) and in leaf total chlorophylls was noticeably lower than in control plants. Root Fe(III)-chelate reductase and phosphoenolpyruvate carboxylase (PEPC) activities were significantly enhanced, but leaf ribulose 1.5-bisphosphate carboxylase (Rubisco) activity was decreased.

This study examined the influence of salt levels on antioxidant activity and content of carotenoids and anthocyanins of the A. hortensis leaves using two varieties: green orach (var. purpurea) and red orach (var. rubra). Seeds of Atriplex were exposed to 0, 90, 180 and 260 mM NaCl for 3 months and seeds were sown in an earthen pot. Overall levels of ascorbate peroxidase (APX) and glutathione reductase (GR) activity were significantly elevated. Salt stress caused a significant decline in tissue concentrations of catalase (CAT) and superoxide dismutase (SOD). However, 90 mM NaCl did not modify these parameters, which remains similar to control values. Activities of APX and CAT were increase whether the shoots of A. hortensis var. purpurea were grown in the presence of 180 mM NaCl. Thus although some indications of oxidative stress accompany exposure of this salt-tolerant Atriplex varieties to salinity, mechanisms appear to exist within its shoot tissue to permit the tolerance of such oxidative stress. High salt concentration in the culture medium provokes oxidative damage in Atriplex leaves and induces a general increase in antioxidant enzyme activity. In particular, NaCl toxicity decreased content of carotenoids. It also decreased the concentration of anthocyanin pigments in leaves of Atriplex. This work therefore provides a starting point towards a better understanding of the role of antioxidant enzyme in the plant response against salt stress.

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