Effects Of Exogenous Spermidine On Physiological And Biochemical Characteristics Of Cerasus Sachalinensis Under Waterlogging Stress

Cerasus sachalinensis is widely cultivated in Dalian as the main rootstock of cherries due to its characteristic of high survival rate,drought-resistant and cold-resistant characteristics.Cherry is a kind of tree species which has poor tolerance to waterlogging stress,and waterlogging stress has become one of the most important factors to restricting its development.Double-pot method was used to simulate the waterlogging stress condition in this experiment,and exogenous Spd to study polyamine metabolism,reactive oxygen metabolism and respiratory metabolism in Cerasus sachalinensis.Study the dynamic changes of key substances and enzyme activities in three metabolisms during 120 hours of waterlogging stress.The main results are as follows:1.Under the stress of waterlogging,the activity of the polyamine metabolic and contents of Spd,Spm and Put in the roots and leaves of the Cerasus sachalinensis was increased.The activities of ADC and SAMDC which are the key enzymes of polyamine synthesis was increased significantly.Exogenous Spd promoted the activity of leaf and root polyamine metabolism,and further increased the content of Spd and Spm in Cerasus sachalinensis.However,the content of Put is lower than the content of Put in CK and the activity of SAMDC was further increased.It means that exogenous Spd promoted the conversion of Put to Spd.The polyamine degradation key enzymes DAO and PAO showed a trend of increasing first and then decreasing.Exogenous Spd inhibited the activity of DAO to a certain extent and increased the activity of PAO.2.Under the stress of waterlogging,the respiratory metabolism of the roots of Cerasus sachalinensis seedlings was blocked.With the increase of waterlogging time,the total respiration rate of the roots of Cerasus sachalinensis seedlings showed a downward trend.In the early stage of the waterlogging stress,the respiratory rate of the EMP respiratory pathway increased,and the respiratory rate decreased in the later stage.Under the waterlogging stress,the respiratory rate of the PPP and TCA pathways was also inhibited.The product of the EMP respiratory pathway,pyruvate,is increased by anaerobic respiration metabolism,and anaerobic respiratory metabolic activity is increased.To a certain extent,exogenous Spd treatment reduced the damage of waterlogging stress on the roots of Cerasus sachalinensis.Exogenous Spd treatment,ATP content and respiration rate in Cerasus sachalinensis were improved compared with the CK in the late stage of waterlogging stress.The fructose content in the EMP pathway is significantly higher than that of CK,and the key enzyme activity of the EMP pathway is also increased compared with CK.ExogenousSpd treatment,the rate of TCA respiratory pathway in roots is higher than CK.The activity of ICDH,a key enzyme in the TCA cycle,is significantly higher than that of CK.MDH and SDH activities were significantly higher than CK after 72 h of waterlogging stress.The key enzyme activity of the PPP pathway is elevated and the respiratory rate of the PPP pathway is increased.Exogenous Spd treatment promoted the accumulation of pyruvate in the root EMP pathway,and the activities of anaerobic respiration key enzymes like LDH,ADH and PDC increased.3.Under the stress of waterlogging,the active metabolism in the Cerasus sachalinensis is activated,MDA,H2O2 and O2.-accumulate,GSH,GSSG and As A also accumulate in leaves and roots,antioxidant enzymes CAT,SOD,POD,APX,GR,DHAR and MDHAR activities were activated under waterlogging stress.Exogenous Spd treatment can remove active oxygen by increasing the activity of CAT,SOD,POD,APX,GR,DHAR and MDHAR in Cerasus sachalinensis.Moreover,the content of MDA,O2.-and H2O2 is lower than that of CK,which reduces the degree of peroxidation of the membrane lipid in Cerasus sachalinensis.