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Exogenous antioxidant applications enable salt-stressed plants to successfully cope with different environmental stresses. The objectives of this investigation were to study the effects of sequential treatments of proline (Pro), ascorbic acid (AsA), and/or glutathione (GSH) on 100 mM NaCl-stressed cucumber transplant&rsquo, s physio-biochemical and growth traits as well as systems of antioxidant defense. Under salinity stress, different treatment of AsA, Pro, or/and GSH improved growth characteristics, stomatal conductance (gs), enhanced the activities of glutathione reductase (GR), superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT) as well as increased contents of AsA, Pro, and GSH. However, sequential application of antioxidants (GSH-Pro- AsA) significantly exceeded all individual applications, reducing leaf and root Cd2+ and Na+ contents in comparison to the control. In plants grown under NaCl-salt stress, growth characteristics, photosynthetic efficiency, membrane stability index (MSI), relative water content (RWC), contents of root and leaf K+ and Ca2+, and ratios of K+/Na+ and Ca2+/Na+ were notably reduced, while leaf contents of non-enzymatic and enzymatic antioxidants, as well as root and leaf Cd2+ and Na+ concentrations were remarkably increased. However, AsA, Pro, or/and GSH treatments significantly improved all investigated growth characteristics, photosynthetic efficiency, RWC and MSI, as well as AsA, Pro, and GSH, and enzymatic activity, leaf and root K+ and Ca2+ contents and their ratios to Na+, while significantly reduced leaf and root Cd2+ and Na+ contents.

Plants face a lot of abiotic stresses, during their life cycle, including salinity that greatly influences their growth and entire metabolism. Osmoprotectants have to enable plant to beat such stress. Two-season field experiments were conducted consecutively in 2015/16 and 2016/17 to study the effect of glycine betaine (GB) foliar application at three levels (0; a control, 25 and 50 mM) on onion growth, physio-biochemical attributes and antioxidant defense system activity was investigated under 4.80 dS m−1 salt stress. Under saline soil conditions, GB treatment significantly increased growth indices (e.g., shoot length, leaves area of plant−1, shoot fresh and dry weights), bulb yields and water use efficiency (WUE), leaf chlorophylls contents and their efficiency, stomatal conductance and tissue health measured as relative water content and membrane stability index. Additionally, endogenous osmoprotectants (e.g., GB and choline) contents, non-enzymatic antioxidants (e.g., glutathione and ascorbic acid) contents and enzymatic antioxidants (e.g., catalase, superoxide dismutase, and ascorbate peroxidase) were significantly increased with exogenous GB application under salt stress. In contrast, glutathione reductase activity was reduced, while free proline and soluble sugars contents were not affected. A level of 50 mM GB was more effective to be the better treatment by which this study recommends to use for growing onion plants under moderate salt stress.

Soil salinity is one of the major problems of agriculture that limits plant performance, particularly in arid and semiarid regions. Therefore, the effect of potassium humate (KH) and α-tocopherol (TOC), used singly or in integration, on soil characteristics, and on plant performance, physio-biochemical attributes and antioxidative defense system of Phaseolus vulgaris L. plants grown under salt stress (EC = 6.35–6.42 dS m−1) was investigated. Half g KH kg−1 soil was used as soil amendment before sowing and 1.0 mM TOC was used as foliar spray twice; at 25 and 40 days after sowing. Results showed that, KH significantly improved soil physical and chemical properties, which positively reflected on plant growth and productivity, physio-biochemical attributes, mineral nutrients (N, P, K and Ca), osmoprotectants (soluble sugars and proline), non-enzymatic (ascorbic acid, glutathione and TOC) and enzymatic (superoxide dismutase, catalase and guaiacol peroxidase (GPOX)) antioxidants compared to untreated co...

Salinity is one of the most limiting abiotic stresses in agricultural productivity. Exogenously applied antioxidants successfully enabled salt-stressed plants to cope with stress. Two-season field experiments were conducted consecutively in 2016/17 and 2017/18 to study the effects of foliar applications of singular (ascorbate, AsA, proline, Pro, and glutathione, GSH) or sequential (AsA-Pro-GSH and GSH-Pro-AsA) antioxidants on growth, yield, physio-biochemical attributes, and enzymatic and non-enzymatic antioxidative defense system of Vicia faba L. (CV. Sakha-1) plants grown under saline soil conditions (EC = 4.53 dS m−1). Under soil salinity conditions, AsA, Pro, or GSH-Pro-ASA improved growth and productivity, photosynthesis efficiency, stomatal conductance (gs), plant water status, as well as enzymatic and non-enzymatic antioxidants. However, sequential AsA-Pro-GSH foliar application followed by singular GSH significantly exceeded all other treatments (i.e., AsA, Pro, and GSH-Pro-AsA), improving growth characteristics (shoot length, shoot fresh and dry weights, and leaves area), photosynthesis efficiency, stomatal conductance, plant water status, and yield and its components (green pods weight/plant−1, green pods yield/hectare−1, and seed yield/hectare−1), as well as enzymatic (ascorbate peroxidase, catalase, superoxide dismutase, and glutathione reductase) and non-enzymatic (AsA, GSH, Pro, phenolic aglycone, phenolic glycosides) antioxidants compared to control. Overall, our results clearly demonstrate that sequential AsA-Pro-GSH foliar application has a positive effect on salt-stressed Vicia faba plants.

The role of antioxidants exogenously-applied individually or in sequences in the improvement of salt tolerance in maize seedlings, and their effects on changes in the activities of endogenous enzymatic and non-enzymatic antioxidants, and the concentrations of phytohormones in seedlings grown under 100 mM NaCl stress were assessed. The efficiency of maize seedlings to tolerate salt stress in terms of growth was noticed to varying degrees with antioxidants applied singly or in sequences. The healthy growth of salt-stressed seedlings was correlated with the improvements in the activities of enzymatic and non-enzymatic antioxidants, the concentrations of osmoprotectants and phytohormones, and tissue health in terms of relative water content and membrane stability index. Results show that, seed soaking in AsA, GSH and proline applied in sequences (i.e., AsA 0.50 -Pro 0.50 -GSH 0.50 or GSH 0.50 -Pro 0.50 -AsA 0.50 ) was better than their applications individually. In addition, the sequenced application of AsA 0.50 -Pro 0.50 -GSH 0.50 as integrated treatment was better, generating maize seedlings more tolerant to salinity than those generated from the sequenced application of GSH 0.50 -Pro 0.50 -AsA 0.50 . Therefore, we recommend using the sequenced application of AsA 0.50 -Pro 0.50 -GSH 0.50 as integrated soaking treatment for maize to grow under salt stress.

The effect of a novel organo-mineral fertilizer (OMF) compost, as a partial alternative to mineral fertilizers, on soil characteristics, growth, physio-biochemical attributes, Cd2+ and NO3 − concentrations, and yields of Phaseolus vulgaris L. plants grown under salt stress was investigated. Six organic and mineral materials were well mixed with water and composted in a polyvinyl house in a concrete trench of size 4 × 5 × 2 m (W × L × D), respectively. The moisture content was maintained at 50–60% throughout the active composting period by frequent checking. The mixture was turned at 7-day intervals for about 2 months to maintain porosity. This OMF compost was applied for the tested saline soil at 10, 20 and 30 ton ha−1 while reducing the recommended NPK to 50%. In addition,100% NPK was applied as a control to achieve the purpose of this study. Growth characteristics, quantitative and qualitative yield, Cd2+ and NO3 − concentrations, and physio-biochemical attributes in common bean plants were assessed. Addition of OMF compost improved the soil chemical and physical properties. Application of OMF compost at a rate of 20 ton h−1, as an alternative to 50% of the recommended dose of mineral-NPK fertilizers, significantly decreased the concentrations of Cd2+ and NO3 − in plant leaves, pods and seeds, showing the same growth characteristics, and pod and seed yields compared to the control (100% of mineral-NPK fertilizers). This treatment also improved all determined physio-biochemical attributes and tested soil characteristics compared to the control. The benefit of this OMF compost, as a partial alternative to chemical fertilizers, demonstrated the validity and possibility of sustainable agronomic performance of common bean using locally available recycled organic materials for manufacturing the studied OMF.

Seaweeds are potentially excellent sources of highly bioactive materials that could represent useful leads in the alleviation of salinity stress. The effects of presoaking wheat grains in water extract ofUlva lactucaon growth, some enzymatic activities, and protein pattern of salinized plants were investigated in this study. Algal presoaking of grains demonstrated a highly significant enhancement in the percentage of seed germination and growth parameters. The activity of superoxide dismutase (SOD) and catalase (CAT) increased with increasing the algal extract concentration while activity of ascorbate peroxidase (APX) and glutathione reductase (GR) was decreased with increasing concentration of algal extract more than 1% (w/v). The protein pattern of wheat seedling showed 12 newly formed bands as result of algal extract treatments compared with control. The bioactive components inU. lactucaextract such as ascorbic acid, betaine, glutathione, and proline could potentially participate in the alleviation of salinity stress. Therefore, algal presoaking is proved to be an effective technique to improve the growth of wheat seedlings under salt stress conditions.