Changes in Activity of Malate Dehydrogenase, Catalase, Peroxidase and Superoxide Dismutase in Leaves of Halimione portulacoides (L.) Aellen Exposed to High Sodium Chloride Concentrations

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Abstract
Plants of H. portulacoides were grown in nutrient solutions containing NaCl at concentrations ranging from 0-2.0 M NaCl. They survived in this environment at least for 20 days. Malate dehydrogenase (MDH), catalase, peroxidase and superoxide dismutase (SOD) were extracted from the leaves of such plants and enzyme activity was assayed in the absence of salt. NaCl at low concentration (0-0.5 M) stimulated the activities of MDH and catalase, but inhibited them at concentrations higher than 0.5 M. Peroxidase and SOD were hardly affected by exposure to salinity in vivo. Salinity in vivo affected the Km and the Vmax of the enzymes. The possibility that the 3 enzymes (catalase, peroxidase and SOD) have a role in protecting the leaf cells against oxygen toxicity caused by free radicals that may be formed in cells when growing under saline and extreme climatic conditions, is discussed.