الفهرس 
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Abstract
Seeds of sunflower are excellent source of many vital nutrients including Vitamin E or α-tocopherol which work as an antioxidant. Sunflower seeds are one of the best natural sources of this antioxidant. It fights against free radical damage. On the other hand, gamma rays are the most energetic form of electromagnetic radiation and fall into the category of ionizing radiation and interact with atoms or molecules to produce free radicals in cells which can disrupt or modify the components of plants. These radiations can be applied to cause genetic variability that is not existed in nature and is not available to the breeder. This study aims to: Investigate the influence of gamma radiation on seed germination, content of reactive oxygen species (ROS), activities of some metabolic enzymes and metabolic compounds of Helianthus annus L and also, investigate the possibility of increasing the level of the antioxidant in H. annus to be a natural source for the antioxidant instead of synthetic antioxidants which have side effects on human health. Seeds of H.annus. were treated with different doses of γ-ray (100, 200, 300, 400, 500, 600, 700, 800 Gray) using cobalt-60 source the process was carried out in Egyptian Atomic Energy Authority (EAEA), Cairo. Seeds which used as a control were not radiated. The results in this investigation revealed that treatment with gamma rays specially at doses ranged between (100:300 Gray) increased the content of secondary metabolites including total phenol, glutathione, flavonoid, tannin, ascorbate content in H. annus and this could be used for production of naturally antioxidant and secondary metabolites at this moderate gamma rays doses.