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Glutathione transferases (GSTs) play a crucial role in detoxification processes due to the fact of their glutathione (GSH) conjugating activity, and through glutathione peroxidase or dehydroascorbate reductase (DHAR) activities, they influence the redox state of GSH and ascorbate (AsA). The plant-specific tau (GSTU) group is the largest class of <i>Arabidopsis</i> GSTs, and their members are involved in responses to different abiotic stresses. We investigated the effect of salt stress on two-week-old <i>Arabidopsis</i> <i>thaliana</i> wild-type (Col-0), <i>Atgstu19</i> and <i>Atgstu24</i> mutant plants after applying 150 mM NaCl for two days. The <i>Atgstu19</i> seedlings had lower GST activity and vitality both under control conditions and after salt stress than the wild-type, but the level of total ROS was similar to the Col-0 plants. The GST activity of the knockout <i>Atgstu24</i> mutant was even higher under control conditions compared to the Col-0 plants, while the ROS level and its vitality did not differ significantly from the wild-type. Analysis of the <i>AtGSTU</i> expression pattern revealed that the mutation in a single <i>AtGSTU</i> gene was accompanied by the up- and downregulation of several other <i>AtGSTUs</i>. Moreover, elevated AsA and GSH levels, an altered GSH redox potential and increased DHAR and glutathione reductase activities could help to compensate for the mutation of <i>AtGSTU</i> genes. The observed changes in the mutants suggest that the investigated isoenzymes influence the redox homeostasis under control conditions and after NaCl treatment in <i>Arabidopsis</i> seedlings. These data indicate for the first time the more general role of a temporary shift of redox status as part of GST mechanisms and regulation.