| The nature of abundant lipid and protein contents,together with high water contents,lead to the stored soybean seeds might suffer from deterioration and aging,which affect the quality of soybean.Massive experiments indicated that ROS and MDA contents increase with the decrease of antioxidant enzyme activity during artificial aging.It is believed that lipid peroxidation is the major cause of seed aging.However,which lipid is more sensitive to aging and whether imbibition repaired or aggravated the cell membrane damage during aging is still unclear.In this study,soybean varieties "Zhong dou 27" was used.We investigated the influences of aging on the main compositions of lipid and fatty acids of soybean from the perspective of lipidomics,and built up the lipid profiles of soybean.We also studied the relationship between lipids and reactive oxygen species from the perspective of the antioxidant system,which may benefit the understanding the seed aging mechanism in the process of aging.The main results obtained from our research as follows:1.The lipid compositions of soybean embryonic axes:soybean is mainly composed of Glycerolipids,Glycerophspholipids,Saccharolipids,Sterollipids,Sphingolipids,Fatty acyls,Prenol lipids and Polyketides.Among them,the Glycerolipids content is highest,and it is about 59.28%of total soybean lipids.There are six kinds of Glycerolphospholipids in soybean seed,which is Phosphatidylcholine,Phosphatidic acid,Phospha-tidylethanolamine,Phosphatidylinositol,Phosphatidylglycerol and Phosp-hatidylserine.The content of Phosphatidylcholine is the most abundant among them,and others are all very low.Fatty acids of soybean mainly consist of linoleic acid,palmitic acid and stearic acid.The linoleic acid content accounted for about 55%of the total fatty acids.2.The effect of aging treatments on the total lipid content of soybean hypocotyl is not significantly,and the relative contents of different types of lipid effect is much significantly,in which glyceridelipids content increased slightly.Compared with the seeds without aging treatments,the Glycerolipids content increased by 1.8%,3.3%and 5.1%with the decrease of the germination rate.However,Glycerolphospholipid content is significantly reduced,the content of the seeds with the germination rate of 85%,46%and 20%,was reduced by 5.8%,24.7 and 36%,respectively.Aging treatments lead fatty acids to significantly reduce.In addition,unsaturated index decreased significantly because of ageing.3.Aging treatments affected the cell membrane structure.Phosphatidylcholine is the major component of the cell membrane.The content of Phosphatidylcholine,Phosphatidylethanolamine,Phosphatidic acid,phosphatidylserine and phosphatidylinositol decreased significantly because of ageing.But the content of Phosphatidylglycerol raised with the germination rate decreased.Compared with aging seeds,Phosphatidylcholine was reduced by 5%,26.7%and 5%,respectively,which the germination rate reduced.Aging treantments damaged the cell membrane structure,and intracellular materials were leaked,which caused the relative conductivity increased.Besides,the lower germination rate,the higher relative electrical conductivity.Under laser confocal microscope,we investigated that aging damaged the cell membrane structure,reduced the fluorescence of outer membrane of cells,and enhanced the fluorescence of intracellular materials.Aging leaded to cell membrane peroxidation,and compared with the aging seeds the MDA content increased by 27%,144%and 152%.4.Aging treatments leaded ROS content of soybean embryonic axes to increase with destroying the antioxidant system and leading to reduce the activity of Hydrogen Peroxide,Ascorbic Acid Peroxidase and Glutathione Reductase.Aging leaded to the accumulation of reactive oxygen species,which damaged the balance of antioxidant system and resulted in peroxidation.5.Imbibition may repair the changes caused by aging and peroxidation.Compared with dry seed,the activity of antioxidant enzymes of seeds with 24 h imbibition treatment tended to be higher,and the relative electrical conductivity are relatively low.The contents of Phosphatidylcholine and Phosphatidylethanolamine of seed with 0 h imbibition decreased continuously.But for the seeds with 24h imbibition treatment,the content is lowest when the germination rate of seed is 46%,and then the content increased again.In conclusion,aging destroyed the antioxidant system,which leaded to the accumulation of a mount of ROS.Reactive oxygen species against lipid unsaturated bond,leaded the contents of Phosphatidylcholine,Phosphatidylethanolamine,Phosphatidic acid,Phosphatidylserine and Phosphatidylinositol decreased significantly.Aging also caused the main fatty acids linoleic acid,palmitic acid and stearic acid content decreased significantly.Finally,the function and structure of cell membrane were destroyed,which characterized by soybean vitality declined.Besides,imbibition may repair the changes caused by aging and peroxidation.In the early stage of the aging,the effect of repair is little.As the germination rate reduced,Phosphatidylcholine and Phosphatidyle-thanolamine lipid contents of seed with the treatment of 24h-imbibition began to increase. |
