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چکیده
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Phosphate-based fertilizers (PF) are a major source of rare earth elements (REEs) pollution. The phytotoxicity of REEs is still poorly understood. However, positive impacts of REEs on plant growth may be restricted to certain growth stages or specific soil conditions. Germination of most species is reduced and delayed with a salinity increase, and plant responses may vary greatly depending on species. Medicinal plants has been extensively used in traditional medicine and often cultivated in arid and semiarid regions with salinity problem. In this research, the influence of salinity and lanthanum (La) as a representative REE, on seed germination parameters including germination percentage (GP %), mean germination time (MGT), germination rate (GR), germination index (GI) and seedling vigor index (SVI) in dragonhead (Dracocephalum Moldavica L.) for 14 days were evaluated. This project was designated in a two level factorial experiments based on completely randomized design with four replication. Seeds of dragonhead were examined at different salinity levels (0, -0.5, -0.1 Mpa) and La different concentrations (0, 25, 50, 75 and 100 µM). The range of NaCl was selected to salinity level of groundwater resources using for irrigation in Arak, Iran. Results showed that salinity stress significantly affected dragonhead seed germination characteristics (p<0.05). Mean comparison showed that by increasing salinity, GP, MGT, GR, GI and SVI decreased (p<0.05). The dragonhead seeds endured osmotic potential up to -0/5MPa and the highest GP was observed in this level however increasing salinity causing reduced GP. La did not change the seed germination parameters of dragonhead in comparison to seeds treated with the control treatment. Also, the interaction of salinity and La was not significant. It is concluded that if La has effects on dragonhead germination, it can only occur at solution concentrations above 100 µM or below 0.25 µM. REEs are not known to be nutritionally essential
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