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In recent years, the involvement of nitric oxide (NO) in numerous physiological processes, particularly the mitigation of stress-induced negative effects on plants, has been clarified. Under salinity conditions, plants are subjected to a secondary oxidative stress.  The present work was designed to examine the exogenous application of nitric oxide (NO), in the form of its donor sodium nitroprusside (SNP), in mitigating the deleterious effects of salinity on Zygoph-yllum fabago L. plants. SNP (200 µM) was applied to plants growing medium under saline (200 and 400 mM NaCl) and non-saline conditions. Growth, oxidative stress markers [cell membrane stability index (MSI) and H₂O₂ conc-entration], antioxidant enzymes activities [peroxidase (POX, EC 1.11.1.7) and catalase (CAT, EC 1.11.1.6)], as well as the contents of some antioxidant compounds (flavonoids and carotenoids) were determined. Salinity lowered the shoot and root dry weights, while it enhanced peroxidase and catalase activities. High salinity increased H₂O₂; however, it de-creased the carotenoids content of leaves. Exogenous NO enhanced the growth, MSI, flavonoids and carotenoids co-ntents of salinized plants. In salinity plus SNP treated plants, H₂O₂ concentration and the activities of the examined en-zymes were reduced. Data suggest that a cooperative process is performed by the antioxidant systems in Syrian bean ca-per in order to cope with salinity. Also, the application of exogenous NO was found to be useful in the mitigation of salinity-induced oxidative stress in plants.

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Some rhizobacteria have positive effects on plants growth. Syrian bean-caper (Zygophyllum fabago) is a weed plant with medicinal value. This study was conducted to isolate and identify bacteria from Syrian bean-caper rhizosphere. Characteristics associated with plant growth stimulation, such as phosphate and zinc dissolution, production of Indole acetic acid and antifungal activity, were investigated. The isolates were separately inoculated to the plant and after plant root establishment was ensured, their effectiveness in increasing plant growth in greenhouse conditions was measured. Biochemical and molecular identification results showed that five isolates belonged to the genera Bacillus, Pseudomonas, Pantoea, and Brevibacterium. All five isolates showed some degree of plant growth promotion capabilities. Among the isolates, only the genus Bacillus increased the dry weights of plants significantly. The amount of phosphate solubilization for this isolate was 440 μg ml^-1 and its acid production in the culture medium was higher than that in other isolates. The isolate had zinc solubilisation capability and produced 3.89 mg ml^-1 indole acetic acid. However, this isolate did not show antifungal activity against two fungal pathogens of Aspergillus niger and Botrytis cinerea.  
 
 
 

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In order to investigate the effects of salinity and magnesium (Mg) on the growth parameters, physiological characteristics and content of some metabolites in Syrian bean-caper (Zygophyllum fabago) plants, a factorial experiment with completely randomized design was performed and carried out in perlite with Hoagland solution. The treatments were combinations of two levels of salinity (0 and 300 mM NaCl) and three levels of Mg concentration (2, 4 and 8 mM; 0, 2 and 6 mM over the standard Mg content of Hoagland medium, 2mM, respectively). The simultaneous effect of salinity and Mg did not change the fresh weight of the plants, but increased the dry weight by 50%. Salinity reduced the leaf area, but the presence of Mg improved and even increased the leaf area of the plants. The Mg reduced NAR, while increased LAR and RLGR. Salinity decreased the RLGR. The simultaneous effect of salinity and Mg increased and improved RGR, LWR, RLGR. The tolerance index in saline treatments increased with the presence of Mg, but the R/S ratio showed a significant increase only in salinity condition, however, the presence of Mg moderated it. Salinity reduced the photosynthetic pigments, while the presence of Mg ameliorated the decrease. As a result, salinity and Mg increased the total sugar content of the leaf and reduced the total sugar content of the root. Salinity and Mg reduced the total protein content of all the organs of the plant specimens studied. In general, salinity had a negative effect on the physiological parameters of the Zygophyllum fabago plants, while the application of supplementary Mg improved the growth indices and increased the plants tolerance against salinity.
 
 

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Texture quality is an important factor in evaluating of fruits. The cut surfaces of the apple fruit turn brown because of the oxidation of phenolic compounds, triggered by polyphenol oxidase enzyme. Preventing the oxidation of phenolic substances and changing color of fruit are very important in the food industry. Due to the adverse effects of chemical additives on human health and increasing consumer preference for natural alternative compounds makes an interesting market for natural plant ingredients. This study was conducted to investigate the effect of some chemical and natural compounds including sodium metabisulfite, and citric acid, aromatic waters (sweats) of chicory, licorice and lemongrass on polyphenol oxidase enzyme activity of apple fruits. The activity of polyphenol oxidase was evaluated spectrophotometrically using pyrogallol as substrate. The optimum temperature and pH values were 32 °C and 7, respectively. It was found that the enzyme activity decreased due to use of natural compounds, sodium metabisulfite and citric acid. In conclusion, polyphenol oxidase activity can be reduced to prevent of fruits browning by using suitable natural compounds instead of chemicals.