Effect Of Exogenous Spermidine On Physiology And Polyamine Metabolism Of Maize (Zea Mays L.) Seedlings Under Wterlogging Stress

The effect of exogenous Spd on poysiological properties and polyamine metabolism were investigated under wet and flooding stress by using waterlogging-sensitive genotype Denghai662(DH662)and waterlogging-tolerance genotype Xundan(XD20).The main result were as follows:1,Effect of exogenous Spd on growth and poysiological properties in Maize(Zea mays L.)seedlings under flooding stressDry biomass weight,plant height,RDIR and RWC were significantly decreased after 5days flooding stress in maizeseedlings and amplitude were different in the two of them,there were significantly reduce in DH662 than XD20.The accumulation of MDA and ROS were also significantly increased under floodling stress in of DH662,but the effect was smaller in XD20.SOD,POD activity were rising,while APX,CAT and GR activity declined in XD20,Flooding stress also seriously affected the accumulation of antioxidants,As A content was fell sharply,and GSH content increased in two genetypes.From those,we can knew that SOD and POD had a strong defense capability than APX,CAT and GR in responsing to flooding stress,maize seedling mainly depended on GSH to enhance its resistance.Exogenous Spd relieved the reduce of dry biomass weight,plant height,DWIR and RWC in two genetypes.Exogenous Spd reduced MDA content and ROS accumulation,increased SOD,POD,APX,GR,CAT activity and As A and GSH content in maize leaves.Contents of proline,soluble sugar,soluble protein and free amino acid were also increased after applying Spd.Abilities of antioxidant and osmotic regulation were increased by spraying Spd.Spd improved the growth characteristic of maize seedlings under stress.Alleviated the degree of the membrane lipid peroxidation and cell membrane damage and effectively enhanced ROS removal ability and degradation of toxic metabolites.There were much more influence to DH662 than XD20.2,Effect of exogenous Spd on polyamine metabolism regulation in Maize(Zea mays L.)seedlings under wet and flooding stressFree polyamine contents were increased under wet and floodging stress in maize seedlings,f Put and f Spd contents increased rapidly at the beginning of the stress in XD20,f Put content peaked after 3 days stress,while DH662 had been increased all over the stress time.(f Spd+f Spm)/f Put rised in XD20,but it decreased in DH662.In addition,wet and flooding stress have contributed to the increase of conjugated polyamine contents.PSCC-APs contents in XD20 increased significantly than DH662,while PISCC-Spd and PISCC-Spm contents had no significant difference between the two varieties.Thus,infering that PISCC-Spd and PISCC-Spm contents had little relationship with adversity stress.Meanwhile,ADC and SAMDC activity rised,ODC activity was smaller,PAO activity was on the rise.Studies showed that exogenous Spd can obviously increased the contents of f Spd and f Spm,reduced the content of f Put and(f Spd+f Spm)/f Put ratio increased,the effect was better in DH662.Investigating that sensitive varity DH662 had obvious responce to exogenous regulator under stress to strengthen its resistance.While f Put might be harmful to the growth of maize,f Spd and f Spm effectively alleviated stress damage in DH662.Exogenous Spd can alsopromotes PSCC-PAs and PISCC-PAs contents under stress in XD20(except PISCC-Put content under flooding stress),There were no significant change(except PISCC-Put content)in DH662.Study showed that ADC and PAO activity was significantly reduced under later stress by spraying Spd in DH662,the activity of SAMDC increased.