The effects of different concentrations of NaCl on the activities of antioxidative enzymes in the shoots and roots of soybean (Glycine max [L.] Merr cv. Pershing) inoculated or not with an arbuscular mycorrhizal fungus, Glomus etunicatum Becker & Gerdemann, were studied. Furthermore, the effect of salt acclimated mycorrhizal fungi on the antioxidative enzymes in soybean plants grown under salt stress (100 mM NaCl) was investigated. Activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were increased in the shoots of both mycorrhizal (M) and nonmycorrhizal (NM) plants grown under NaCl salinity. Salinity increased SOD activity in the roots of M and NM plants, but had no effect on CAT and polyphenol oxidase activities in the roots. M plants had greater SOD, POD and ascorbate peroxidase activity under salinity. Under salt stress, soybean plants inoculated with salt pre-treated mycorrhizal fungi showed increased SOD and POD activity in shoots, relative to those inoculated with the non pretreated fungi.

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The effects of water‐deficit stress and foliar application of ascorbic acid were studied in leaves of Zea mays L. (single cross 704). The activity of antioxidant enzymes, superoxide dismutase, peroxidase, catalase and polyphenol oxidase was clearly increased by water‐deficit stress. Foliar application of ascorbic acid reduced stress‐induced and antioxidative enzymes activities. Proline and malondialdehyde levels were decreased in water‐deficit stressed plants by ascorbic acid application. It seems that, ascorbic acid application helps the plants for better resistance under the stress by inactivation and scavenging of free radicals. Chlorophyll content was also decreased by water‐deficit stress. The significant decrease of chlorophyll content was obtained in stressed plant than control. Ascorbate was oxidized to dehydroascorbate whereupon total ascorbate was decreased and dehydroascorbate was increased in leaves. The results of the present study indicated that ascorbic acid reduced the harmful effects of reactive oxygen species and improved plant resistance to water stress. In brief, ascorbic acid treatment reduced the damaging action of drought and decreased enzyme activity due to scavenging of reactive oxygen species; thereupon it may be effective for the improvement of stressed plants in arid and semi‐arid regions.

A metabolic profiling including calculation of energy cost of amino acids biosynthesis in cultured cells of Scrophularia striata showed that methyl jasmonate-inducible oxidative stress elicited secondary metabolites formation derived from phenylalanine and tyrosine and increased energy cost for these amino acids biosynthesis. Understanding of the metabolic pathways in cell culture of Scrophularia striata, an aromatic plant species, facilitates means of production of pharmaceutical metabolites under oxidative stress. In this study, we evaluated the effects of MeJA on the S. striata metabolic pathway and the responses to oxidative stress. Exposure to methyl jasmonate (MeJA) affects plant growth, effectively induces production of reactive oxygen species (ROS) and inserts oxidative stress at the cellular level which results in alteration of primary metabolites and production of phenylepropanoid compounds. Cells treated with MeJA indicated increase in the activities of three antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPx) as well as intracellular H2O2 and MDA contents compared with mock-treated cells. High performance liquid chromatography (HPLC)-based metabolome analysis revealed dynamic metabolic changes in oxidatively stressed S. striata cells, e.g., general phenylpropanoid pathway, phenylethanoid-glycosides, lignans, and increased energy cost of biosynthesis and accumulation of amino acids. Furthermore, principal component analysis (PCA)-derived score plots demonstrated that MeJA affects cellular metabolism in S. striata cells and significantly alters metabolite composition under MeJA-inducible oxidative stress. These observations suggest that MeJA-elicited cell suspension cultures of S. striata balanced the production of primary and secondary metabolites in coordination with ROS-scavenging system.

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Background: Nitrogen is the most important nutrient requirement for plants. Nitrogen supplying affected the leaf area, carbon fixation, glandular trichomes formation, ATP and NADPH content which resulted to the terpenoids biosynthesis enhancement and essential oils accumulation. Objective: This study was aimed to evaluate changes of essential oil content and components by use different levels of Urea fertilizer and its relation with the antioxidant status of peppermint. Method: The two field experiments were conducted on randomized complete block design at 2013 and 2014. The treatments consisted of three levels of nitrogen fertilizer (urea) (0, 75, and 150 kg ha -1 ). The evaluated traits were included antioxidant enzymes, essential oil percentage and essential oil components.Results: The urea fertilizer had a significant effect (P≤0.01) on the soluble protein amount and antioxidant enzymes activity. Urea consumption in the both years increased the peppermint essential oil content. The interaction of nitrogen fertilizer and year had a significant effect on most of the essential oil components excepted to β-pinene, myrcene, Limonene, 1,8-Cineole, Z-β-Ocimene, and α-Terpineol. Conclusion:Using nitrogen fertilizer increased the peppermint essential oil content. Also, nitrogen deficiency reduced the soluble proteins and essential oil content and in contrast, it increased antioxidant enzymes activity and pulegone content. Therefore, consumption of 75 kg urea per hectare is recommended due to increasing essential oil content, decreasing pulegone rate, and no significant effect on menthol, menthone, and menthofuran contents.

One of the inevitable consequences of drought stress is enhanced production of reactive oxygen species (ROS). Fructan might function as effective candidate for capturing ROS in a wide range of stresses. Herein, 4-day-old seedlings of drought-tolerant and -sensitive wheat cultivars were exposed to drought stress for 7 days by water cessation, followed by further 7 days re-watering. The content, metabolism, related enzymes activity, degree of polymerisation (DP) and antioxidant capacity of fructan were compared in the two cultivars. High resolution HPAEC-PAD analysis of fructan showed an increase in the activities of fructan: fructan 1-fructosyltransferase (1-FFT) in the tolerant cultivar and sucrose: sucrose 1-fructosyltransferase (1-SST) and 1-FFT in the sensitive cultivar under drought condition. The activity of fructan exohydrolase (FEH) did not show any significant change in tolerant cultivar, but decreased in a sensitive one. In comparison with the sensitive cultivar, the tolerant one accumulated fructan (0.9% of dry matter) with higher degree of polymerisation (10.67 ± 1.1), accompanied by increased OH radical scavenging activity, during drought condition. In regard to the fact that OH radical is the most prevalent ROS in damaging membrane lipids, the results suggest that fructans play a crucial role in the tolerance of wheat seedlings against drought stress.

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