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Salt treatment strongly affected cell growth by decreasing dry weight. Exposure of Catharanthus roseus cell suspensions to increasing salinity significantly enhanced total lipid (TL) content. The observed increase is mainly due to high level of phospholipids (PL). Hundred mM NaCl treatment increased phospholipid species phosphatidylcholine (PC) and phosphatidylethanolamine (PE), whereas it reduced glycolipid ones monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) but not sulfoquinovosyldiacylglycerol (SQDG). Moreover, fatty acid composition was clearly modified when cells were cultured in the presence of 100 mM NaCl, whereas only few changes occurred at 50 mM. Salt treatment decreased palmitic acid (16:0) level and increased that of linolenic acid (18:2). Such effect was observed in phospholipid species PC and PE and in glycolipid DGDG. Double bond index (DBI) was enhanced more than 2-fold in fatty acids of either glycolipids or phospholipids from cells submitted to 100 mM NaCl. Free sterol content was also significantly enhanced, especially at 100 mM NaCl, whereas free sterols/phospholipids (St/PL) ratio was slightly decreased. All these salt-induced changes in membrane lipids suggest an increase in membrane fluidity of C. roseus cells. [Copyright &y& Elsevier]

Pretreatment in arboriculture is a new physiological approach allowing the improvement of plant tolerance to salt stress. This research aims to screen various pretreatments of salicylic acid (SA) and/or calcium chloride (CaCl 2 ) to mitigate the effect of salinity on ‘Oueslati ’ olive plants ( Olea europeae L.) on physiological attributes under 200 mmol L −1 of NaCl application. One - year- old plants were transplanted to sand culture in a greenhouse, and were pretreated with two levels of foliar application of SA (0.5 and 1 mmol L −1 ) and by adding CaCl 2 (10 and 20 mmol L −1 ) to the culture solution twice a week for 45 days. At the end of the pretreatment, the plants were subjected to 200 mmol L −1 NaCl exposure for 75 days. The result showed that shoots and roots growth were decreased significantly due to salinity, sodium (Na + ) ions increased and K + /Na + ratio decreased in leaves. Rate of assimilation ( A ), transpiration ( E ) and stomatal conductance ( g s ) decreased in leaves. Salinity caused significant increase in both malondialdehyde (MDA) and H 2 O 2 concentration, a decrease in total polyphenol and flavonoid levels and an increase in scavenging activity (IC50) (21%). Moreover, salinity caused a decrease in xylem and an increase in phloem thickness in leaves. However, pretreatments could partly improve the adverse effects of salinity on the most studied parameters. SA (1 mmol L −1 ) is able to restrict Na + ions transport from the roots to the leaves limiting its toxicity in the sensitive organs. SA (1 mmol L −1 ) and CaCl 2 (10 mmol L −1 ) pretreatment alleviate the effects of salinity on dry weight of shoots and roots as well as, photosynthetic activity in pretreated plants. Moreover, at the same pretreatment, results showed a decrease of the Na + translocation to the leaves. Furthermore, it has been shown that pretreatment of ‘Oueslati’ olive plants enhance the non-enzymatic antioxidant activity (total polyphenol and flavonoid content).These results suggest that pretreatments may be useful methods to increase salt tolerance in olive, for use in arid and semi-arid environments. [ABSTRACT FROM AUTHOR]

The effects of potassium (K + ) deficiency were investigated in Sulla carnosa plants. Plants were grown hydroponically for one month in K + -sufficient (6 mM K + , Control) and K + -deficient (60 μm K + ) solutions inside the greenhouse in Biotechnology Center of Borj Cedria, Tunisia. Growth, water status, pigment contents, photosynthetic gas exchange, photosystem II (PSII) photochemistry and leaf principal secondary metabolites (polyphenols, flavonoids, and condensed tannins), and their antioxidant properties (DPPH (1.1-diphenyl-2-picrylhydrazyl) scavenging capacity, ferric reducing power, chelating effect on ferrous ions, and β-carotene bleaching test) were determined. Growth of vegetative organs was decreased by some 50% by K + deficiency with stems more affected (−68%) than roots (−42%) and leaves (−45%). Water content decreased in the three vegetative organs. Photosynthetic gas exchange and pigment contents were affected by low K + conditions. In contrast to condensed tannins which remained constant, total polyphenols and flavonoids contents increased under K + deficiency (by 62.7 and 14.5%, respectively). Furthermore, total antioxidant activity increased by 33.5% compared to control plants. Except for β-carotene bleaching test that increased, DPPH scavenging capacity, ferric reducing antioxidant power, and chelating effect on ferrous ions decreased owing to K + deficiency. An increased and/or de novo synthesis of individual polyphenols was also observed by RP-HPLC analysis. As a whole, these data suggest that S. carnosa was able to modulate the metabolism of secondary metabolites and their antioxidant activity under conditions favouring reactive oxygen species (ROS) production in order to minimize the deleterious effects of these oxygen species. [ABSTRACT FROM AUTHOR]

The possibility to use membrane-lipid measurements to screen barley genotypes for salt resistance was studied. The results showed that wild barley ( Hordeum maritimum) displayed a typical halophytic response as compared to cultivated barley ( Hordeum vulgare L. cv. Manel). Growth, tissue hydration, and photosynthetic activity were less affected by salinity in H. maritimum than in H. vulgare. The induced effects of long-term NaCl treatment were reflected in root membrane lipids that remained relatively unchanged in wild barley, whilst they were significantly diminished with increasing salinity in H. vulgare. The levels of membrane-lipid peroxidation and electrolyte leakage were changed only at high salt concentrations in H. maritimum whereas those of H. vulgare were considerably increased by lower salinity levels as a result of oxidative damage. These findings indicate that maintained membrane integrity (in H. Maritimum) may be considered a possible trait for salt resistance. However, membrane fluidity in H. vulgare was more increased than in H. maritimum. Thus, the unsaturated-to-saturated fatty acid ratio (UFAs : SFAs) and the double-bond index (DBI), significantly increased in response to salt stress in cultivated barley while it did not change in H. maritimum. The changes in lipid unsaturation were predominantly due to increases in linolenic (C18:3), linoleic (C18:2), and oleic (C18:1) acids and decreases in stearic acid (C18:0). These results suggest that, in spite of being important for maintenance of membrane fluidity, the ability to increase unsaturation is not a determinant factor for salt resistance in barley species. [ABSTRACT FROM AUTHOR]