en Effects of Drought Stress during Seed Development and Subsequent Accelerated Ageing on Wheat Seed Mitochondrial Ultra-structure, Seedling Antioxidant Enzymes, and Malondialdehyde تنش خشكي Droughts Stress پژوهشي Research In this experiment, wheat plants were exposed to drought stress during seed development then we worked on the obtained seeds. The seed mitochondrial ultra-structure, and antioxidant enzymes in seedling were investigated after exposure to seed accelerated ageing. Drought stress during seed development induced some changes in mitochondrial ultra-structure. Encountering seed development to drought stress decreased antioxidant enzymes activity and increased H₂O₂ in the seedling. Seed accelerated ageing declined antioxidant enzyme activity and increased malondialdehyde. Mitochondrial ultra-structure also showed heavy damage after accelerated ageing. Most damages in mitochondrial ultra-structure were observed in the seeds obtained from drought-stressed plants then exposed to accelerated ageing. A swollen form of mitochondria with less crista was observed in the seed that exposed to accelerated aging. Damage to mitochondria may be the main cause for seed ageing. However, the activity of antioxidant enzymes is a key factor in order to repair the damage and inhibit the lipid peroxidation resulted in maintaining cell membrane integrity in aged wheat seeds. In this experiment, wheat plants were exposed to drought stress during seed development then we worked on the obtained seeds. The seed mitochondrial ultra-structure, and antioxidant enzymes in seedling were investigated after exposure to seed accelerated ageing. Drought stress during seed development induced some changes in mitochondrial ultra-structure. Encountering seed development to drought stress decreased antioxidant enzymes activity and increased H₂O₂ in the seedling. Seed accelerated ageing declined antioxidant enzyme activity and increased malondialdehyde. Mitochondrial ultra-structure also showed heavy damage after accelerated ageing. Most damages in mitochondrial ultra-structure were observed in the seeds obtained from drought-stressed plants then exposed to accelerated ageing. A swollen form of mitochondria with less crista was observed in the seed that exposed to accelerated aging. Damage to mitochondria may be the main cause for seed ageing. However, the activity of antioxidant enzymes is a key factor in order to repair the damage and inhibit the lipid peroxidation resulted in maintaining cell membrane integrity in aged wheat seeds. accelerated ageing, antioxidant defense, late-season drought stress, seed physiology, Triticum aestivum L. accelerated ageing, antioxidant defense, late-season drought stress, seed physiology, Triticum aestivum L. 1 8 http://jispp.iut.ac.ir/browse.php?a_code=A-10-865-4&slc_lang=en&sid=1 Hamid Reza Eisvand eisvand.hr@lu.ac.ir Yes Lorestan University دانشگاه لرستان Saeed Moori s.moori86@gmail.com No Lorestan University دانشگاه لرستان Ahmad Ismaili ismaili_ahmad@yahoo.com No Lorestan University دانشگاه لرستان Shahryar Sasani shahryar_sasani@yahoo.com.au No AREEO, Kermanshah, Iran دانشگاه لرستان