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Abstract
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In this study, seeds of Dracocephalum moldavica were exposed to different concentrations (0, 25, 50 and 75 _mg salinity stress (0, 25, 50 and 100 mM NaCl). The experiment was conducted as a factorial and in a completely randomized block design. In each pot 5 plants hydroponically grown in containing growth chamber of cucupit and perlite with 2:1 ratio. They were daily irrigated with quarter-strength Hoagland solution. Germinated seeds were subsequently allowed to grow in the culture media to test the further response of the seedlings in terms of growth characteristics to the employed treatments. Seeds subjected to salinity showed a reduction in morphological properties in both levels of salt stress and in 100 mM NaCl level was the most. Growth characteristic such as the number of leave, lengths of shoots, fresh weight, number of nodes and rooting percentage of plants. However, the inclusion of ZnO-nanoparticle at the 25 mgl-1 concentration significantly alleviated the salinity stressinduced a reduction in growth attributes and had the significant (p< 0.01) with 50 and 75 mg l-1 concentration of treatment. This happened due to increased water uptake, up-regulation of mechanisms involved in salt tolerance, and reduction in oxidative injury indices including Gpx, PPO, CAT, and APX. The improved plant performance under salinity stress was a consequence of changes in various antioxidant and also biosynthesis of proteins, phenolics, and specific metabolites such as proline. Results demonstrate that treatment by lowest concentration of ZnO-nanoparticle can induce tolerance in seedlings against low to High levels of salinity through enhancing water uptake and activating plant defense system.
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