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Effects of salt stress on the time course of stomatal behaviors and the activity of antioxidative enzymes such as catalase (CAT) (EC 1.11.1.6), ascorbate peroxidase (APX) (EC 1.11.1.11), and glutathione reductase (GR) (EC. 1.6.4.2) were studied in three strawberry cultivars. The responses of the cultivars ‘Camarosa’, ‘Tioga,’ and ‘Chandler’ were compared when they were irrigated with nutrient solution containing 0, 8.5, 17.0, and 34.0 mM sodium chloride (NaCl) for 30 days. A significant reduction in stomatal conductance (gs) was seen particularly on the 30th day of the salt treatments only in Camarosa, which is parallel to transpiration rate (E). CAT activities decreased in all of the salt treatments only in Tioga, while it remained almost unchanged or slightly increased depending on the period in Camarosa and Chandler. APX activity sharply increased in 17.0 and 8.5-mM NaCl treatments for 30 days in Camarosa and Tioga, respectively, whereas it linearly increased based on the NaCl treatments in Chandler. On the other hand, only Camarosa demonstrated a sharp increase in GR activity induced by salinity applied for 30 days. All the data indicated that control of the stomatal behavior, the higher salt-stress tolerance (LT50) and higher constitutive activity of antioxidant enzymes made Camarosa and Tioga relatively salt-tolerant cultivars.
We investigated the propagation of shock waves in a prismatic rectangular channel with a horizontal wet bed. Saltwater was used as a Newtonian fluid within the entire channel instead of normal water for representing the different density fluids. It aims to point out seawater where tsunamis occur as an extreme example of shock waves. The shock waves were generated by sudden lifting of a vertical gate that separated a reservoir and a downstream channel with three different tailwater depths. The experimental data were digitized using image processing techniques. Furthermore, the flow was numerically solved by using Reynolds Averaged Navier-Stokes (RANS) equations and a DualSPHysics program (a code version of smoothed particle hydrodynamics (SPH)). After sudden removal of the vertical gate the propagations of shock waves were experimentally examined via image processing, which can yield both free surface profiles at several times and variations of flow depth with time at four specified locations. Solution successes of two different numerical methods for this rapidly varied unsteady flow are tested by comparing the laboratory data. The results indicate that the disagreements on graphs of time evolutions of water levels obtained from two numerical simulations decrease when the initial tailwater levels increase.
Effects of salt stress on the activity of peroxidase (PRX) isozyme and leaf proteins were studied in the three strawberry varieties, Camarosa, Tioga and Chandler. Plants were watered with modified 1/3 Hoagland nutrient solution containing 0 (control), 8.5, 17.0 and 34.0 mM NaCl for 30 days fallowing 20 days acclimation. PRX activity was assayed in leaf extracts and PRX profiles of control and salt treated plants were performed by native polyacrylamide gel electrophoresis (PAGE).During the salt stress Tioga and Camarosa tolerated the cellular damage with less electrolyte leakage while Chandler exhibited a severe cellular damage with the highest (87.5 % in 34.0 mM NaCl treatment) electrolyte leakage. Total soluble protein content was decreased by salinity in Tioga (from 11.35 to 5.86 mgg-1DW) and Chandler (from 9.35 to 3.90 mgg-1DW) while it was almost unchanged in Camarosa. Salt stress increased total and specific PRX activity as compared with the control in all the varieties. In native PAGE, one basic isoperoxidase band (Rf=0.27) was observed commonly with different band intentity in all the treatments. Therefore, it might be associated with lignification and recovery of cell membrane damage in strawberry plants under salt stress.
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