Effect Of Different Ageing Treatments On Mitochondrial Structure And Antioxidant Systems In Oat Seeds

This experiment was designed to measure the changes in ultrastructure, antioxidant enzymatic activities and lipid peroxidation of embryo cells and mitochondria in aged oat (Avena sativa L.) seeds, and compared the different physiological response between embryo cells and mitochondria, to reveal the mechanism of oat seed ageing from the level of cell and mitochondria. Additionally, this experiment studied the physiological changes in repairs of AsA and GSH treatment, and PEG priming for aged oat seeds by analyzed the changes in mitochondrial ultrastructure and function, to reveal the internal mechanism of oat seed during deterioration. Main results are as follows:Oat seeds with different moisture contents (4%,10%and16%) were aged for0,8,16,24,32and40d in45℃, then determined the changes in the ultrastructure of the embryo cells, antioxidant enzymatic activities and lipid peroxidation. The results showed that the declining in the germination percentage and integrity of cell ultrastructure in oat aged seeds were presented during the aged process, and these changes would be enhanced by the higher moisture content. For oat seeds with4%and10%moisture content, SOD and CAT were much more sensitive than APX at the early stages of imbibition after mild ageing, the activities of SOD, CAT, APX, MDHAR decreased significantly (P<0.05) after being aged from32d to40d, the activities of DHAR and GR increased after mild ageing. The activities of antioxidant enzymes and contents of MDA and H2O2in oat seeds with16%moisture content all gradually decreased after ageing from8d to40d, also the ultrastructure of embryo cells was severely damaged.Oat seeds with different moisture contents (4%,10%and16%) were aged for0,8,16,24,32and40d in45℃, then observed the changes in mitochondrial ultrastructure, antioxidant systems and lipid peroxidation. The results showed that mitochondrial antioxidants in aged oat seeds with a4%moisture content were maintained at a higher level than seeds with a10%and16%moisture content. These results indicated that the levels of mitochondrial antioxidants and malondialdehyde after imbibition were related to the integrity of mitochondrial membrane in aged oat seeds. The scavenging role of mitochondrial SOD was only inhibited at the early stage of seed aging, and MDHAR and DHAR played more important roles than GR in AsA regeneration for aged oat seeds during imbibition.Oat seeds with a10%moisture contents were aged for0,8,16,24,32and40d in45℃, then measured the changes in antioxidant enzymatic activities, MDA and H2O2contents of the embryo cells and mitochondria. The results showed that the level of seed vigor was the consequence of antioxidant enzymes to remove the accumulation of mitochondrial H2O2. The activities of different antioxidant enzymes presented a certain region and sequence during oat seed ageing. The mitochondrial SOD and APX firstly played an important role in eliminating H2O2, thereafter, the MDHAR and DHAR showed a high level to counteract H2O2in embryo cells, but the contribution of GR was very small for removal of H2O2.Aged (in45℃for20d) oat seeds with a10%moisture content were soaked in the solutions of AsA, GSH and AsA+GSH for0.5h, and then determined the changes in the germination percentage, mitochondrial ultrastructure, enzymatic activities and lipid peroxidation of the embryo cells. The results showed that the treatment with AsA, GSH, AsA+GSH were not inhibited the ageingin oat seed. However, they could repair the ageing damage of oat seed, and the repair effect of AsA was higher than GSH for aged oat seeds, but the repair effect of AsA and GSH did not stack. The repair effect of AsA for aged oat seeds mainly depended on the mitochondrial APX and MDHAR, but the repair effect of GSH mainly relied on mitochondrial GR and DHAR. Moreover, mitochondrial APX and MDHAR played more important role than GR and DHAR in counteracting H2O2.Aged (in45℃for48d) oat seeds with a4%moisture content primed with PEG (-1.2MPa) and distilled water for12h, and then determined the changes in the level of seed vigor, mitochondrial ultrastructure, enzymatic activities and lipid peroxidation of the embryo cells. The results showed that PEG priming significantly (P<0.05) improved the activities of mitochondrial enzymatic activities in aged oat seeds, and significantly (P<0.05) declined the H2O2and MDA content in mitochondria, thus, the integrity of mitochondria increased, and the seed vigor enhanced. However, the opposite trend was observed by distilled water priming for12h. This indicated that PEG primig not only repair the damage from oat seed ageing, but also prevent the imbibition damage for ultra-dried oat seeds during germination.