| Summary: | Abstract Background The application of the free radical nitric oxide (NO) donors (arginine and sodium nitroprusside) have protective effects on plants in alleviating salinity stress throughout improving the enzymatic activities of antioxidant enzymes and osmotic adjustment which induced plant antioxidative defense system. This experiment carried out to study the effect of soaking seeds of sunflower plant in different concentrations of arginine or sodium nitroprusside (SNP) on growth, some physiological parameters, yield and chemical composition of the yielded seeds of sunflower under salinity stress. Results Growth parameters (shoot length, stem diameter, no. of leaves, shoot fresh, and dry weights) decreased significantly with salinity stress and such effect ameliorated using the two levels of both arginine and SNP. Photosynthetic pigments significantly increased in the arginine and SNP treated plants under salinity stress or not stressed ones. Phenol and indole acetic acid as well as compatible solutes as total soluble sugar and proline showed highly significant increase with arginine and SNP treatments either in unstressed plants or those under salinity stress conditions. Free amino acids showed significant increase in both unstressed and stressed sunflower plants treated with either arginine or SNP. High level of arginine recorded the highest values of TSS, proline, free AA, phenol, and IAA in both unstressed and salinity stressed plants. Arginine and SNP with salinity levels showed a highly significant increase in various antioxidant enzymes compared to the control plants. Arginine or SNP at all tested concentrations decreased significantly plant content of Na, while K and P highly significantly increased and Ca, Mg, and N non-significantly increased. The yield parameters showed in general highly significant increase in head diameter, 100-seed weight, seed yield/plant, and oil% with arginine or SNP with the superiority of the higher concentration of both treatment materials. Both arginine and SNP increased markedly total unsaturated (TU) fatty acids as well as TU/TS with superiority of high concentration of SNP treatment in that domain. Conclusion Soaking seeds of sunflower plant with arginine and SNP improved yield parameters of sunflower. High level of SNP under salinity stress conditions proved to be the most effective.
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