Effect of high sodium chloride concentrations on the pigment content and free-radical processes in corn seedlings leaves

The effect of sodium chloride on general morphometrical parameters of seedlings, and biochemical parameters in the leaves of corn seedlings was studied. Exposure to 100 and 200 mM NaCl slowed down the growth of stem and roots, whereas 100 and 200 mM NaCl during 24 h enhanced the concentration of chlorophylls, carotenoids, anthocyans, and thiobarbituric acid reactive substances. The decrease in protein carbonyl groups was found at 24-hour exposure to 200 mM salt. The treatment during 24, 48 and 72 h to 200 mM salt increased the level of total and high molecular mass thiols, whereas low molecular mass thiol content was by 20-25% higher at 48 h exposure to all used salt concentrations. The activity of guaiacol peroxidase was higher only at 24 h exposure to 100 and 200 mM salt, and catalase--at 50 mM during 48 h. At 72-hour exposure, catalase activity was by 27 and 41% higher in seedlings, exposed to 50 and 200 mM NaCl, respectively. Therefore, it is concluded the plant exposure to 50-200 mM salt initially developed oxidative stress, inducing adaptive response--an increase in antioxidant potential and efficiency of systems of energy production. That results in plant adaptation to unfavourable conditions.     

Effect of sodium nitroprusside and S-nitrosoglutathione on pigment content and antioxidant system of tocopherol-deficient plants of Arabidopsis thaliana

Sodium nitroprusside (SNP) and S-nitrosoglutathione (GSNO) were used as a source of exogenous nitric oxide (NO) to investigate their effects on biochemical parameters and antioxidant enzyme response in leaves of wild type Columbia and tocopherol-deficient vte4 and vte1 mutant lines of Arabidopsis thaliana plants and possible tocopherol involvement in regulation of antioxidant response under NO-induced stress. SNP enhanced the activity of the enzymes, that scavenge hydrogen peroxide in leaves of all studied lines, and increased glutathione reductase and glutathione-S-transferase activity there. In addition, it decreased the intensity of lipid peroxidation in vte1 mutant line leaves. At the same time, GSNO increased the levels of protein carbonyls and inactivated enzymes ascorbate peroxidase, guaiacol peroxidase and dehydroascorbate reductase in almost all investigated plant lines. In contrast to wild type, GSNO increased superoxide dismutase activity and decreased catalase activity and chlorophyll a/b ratio in the leaves of two mutant lines. It can be assumed that tocopherols in some way are responsible for plant protection against NO-induced stress. However the mechanisms of this protection remain unknown.     

Effect of short-term salt stress on oxidative stress markers and antioxidant enzymes activity in tocopherol-deficient Arabidopsis thaliana plants

Changes of carotenoids and anthocyanins content, lipid peroxidation, and activity of antioxidant enzymes were studied in wild type and tocopherol-deficient lines vte1 and vte4 of Arabidopsis thaliana subjected to 200 mM NaCI during 24 h. The salt stress enhanced the intensity of lipid peroxidation to different extent in all three plant lines. Salt stress resulted in an increase of carotenoid content and activity of catalase, ascorbate peroxidase, guaiacol peroxidase and glutathione reductase in wild type and tocopherol-deficient vte1 mutant. However, the increase in anthocyanins concentration was observed in vte1 mutants only. In vte4 mutant, which contain gamma-tocopherol instead of alpha-tocopherol, the response to salt stress occurred via coordinative action of superoxide dismutase and enzymes of ascorbate-glutathione cycle, in particular, ascorbate peroxidase, glutathione reductase, dehydroascorbate reductase, and glutathione-S-transferase. It can be concluded, that salt stress was accompanied by oxidative stress in three studied lines, however different mechanisms involved in adaptation of wild type and tocopherol-deficient lines to salt stress.     

Effect of sodium chloride and nitroprusside on protein carbonyl groups content and antioxidant enzyme activity in leaves of corn seedlings Zea mays L

The effect of sodium nitroprusside (SNP) and sodium chloride (NaCl) on protein carbonyl group content and activity of antioxidant enzymes was investigated in leaves of maize seedlings. Incubation with NaCl and SNP+NaCl increased the content of carbonyl proteins after 24 h. Treatment with SNP+NaCl during 48 h showed lower and after 72 h higher carbonyl protein content than that in the control. Catalase activity was higher in the leaves of SNP+NaCl-treated than in the leaves of SNP-treated seedlings after 24 h. Ascorbate peroxidase activity increased after incubation with 0.2 mM SNP for 24 h. Significant increment of guaiacol peroxidase activity was obtained in all treated groups in comparison with the control after 72 h. Glutathione-S-transferase activity increased after 48 h seedling treatment with NaCl or SNP and 72 h seedling incubation with NaCl. Under experimental conditions used, glutathione reductase activity was virtually not affected. It is proposed that SNP can be used to prevent salt-induced oxidative stress in maize.