The Study On The Effect Of Exogenous Spermidine On Alleviating Drought Stress In The Seedlings Of Hordeun Jubatum

Hordeum jubatum is an ornamental grass with a great application potential in northeast of China.Under the severe situation of fresh water and urban green irrigation water shortage,it is essential for improving the drought resistance of Hordeum jubatum to utilize its ornamental value.By applying different concentrations of Spd(0,0.5,1.0,1.5 mmol·L-1)to Hordeum jubatum leaves,we study the effect of Spd on drought lasted for 0,5,10 and 15 days of Hordeum jubatum.The main research conclusions are as follows:(1)Exogenous Spd promote the growth of Hordeum jubatum leaves under drought stress.The degree of necrosis and yellowing in Hordeum jubatum leaves gradually increased under drought stress,the rate of leaf biomass and water content significantly decreased,and the daily growth rate showed a trend of increasing first and then decreasing.Applying exogenous Spd significantly alleviated leaves yellowing.Applying exogenous Spd promoted leaves elongation,leaf biomass and daily growth rate under drought stress(P<0.05).At 1-10 days of drought stress,the effect of 1.0 mmol·L-1 exogenous Spd is better.With drought stress lasting for 11-15 days,1.5 mmol·L-1 exogenous Spd have the most obvious effect.(2)Exogenous Spd regulate the photosynthetic activity of Hordeum jubatum leaves under drought stress.Under drought stress,the Pn,Gs,Ci,Tr,Chi a,Car,Fv/Fm,? PS ? and qp of Hordeum jubatum leaves were all decreased significantly,and only improved NPQ(P<0.05).Applying exogenous Spd significantly improved Pn,Gs,Ci,Tr,Chi a,Car,Fv/Fm,? PS ? and qp and only reduced NPQ(P<0.05).At 1-10 days of drought stress,the effect of 1.0 mmol·L-1 exogenous Spd is better on the photosynthesis of Hordeum jubatum leaves.With drought stress lasting for 11-15 days,1.5 mmol·L-1 exogenous Spd have the most obvious effect.(3)Exogenous Spd enhance the antioxidant capacity of Hordeum jubatum leaves under drought stress.The activity of SOD and CAT in leaves increased first and then decreased,while the activity of POD and APX increased gradually under drought stress.Applying exogenous Spd significantly increased SOD,POD,CAT and APX activities in Hordeum jubatum leaves(P<0.05).The effect of applying 1.0-1.5 mmol·L-1 exogenous Spd to improve the antioxidant capacity of Hordeum jubatum leaves is better.(4)Exogenous Spd maintain osmotic balance of Hordeum jubatum leaves under drought stress.The content of malondialdehyde,soluble protein,proline and soluble sugar in leaves increased gradually under drought stress,Applying exogenous Spd significantly increased the content of soluble protein,proline and soluble sugar.Malondialdehyde content in leaves significantly decreased(P<0.05).The effect of applying 1.0-1.5 mmol·L-1 exogenous Spd to maintain osmotic balance of Hordeum jubatum leaves is better.