| In order to probe the response mechanism of Zelkova schneideriana to water stress and compare drought and waterlogging tolerance of three Zelkova schneideriana varieties,this thesis selected the annual grafted seedlings of Zelkova schneideriana "Xingfu’,Zelkova schneideriana ’Hentiangao’ and Zelkova schneideriana ’Linyuan’ as experimental materials,by using pot water control experiment,and artificially simulating Slight Drought Stress,Middle Drought Stress,Hight Drought Stress,Natural Drought Stress,and Waterlogging Stress.During the experiment,the physiological and biochemical indicators of the experimental materials were measured.These indicators include plant height,drought(waterlogging)injury index,relative electrical conductivity,malondialdenhyde content,soluble sugar content,free proline content,peroxidase activity,superoxidedismutase activity,chlorophyll content and water saturation deficit.Through this method to screen suitable physiological indicators for evaluating drought and waterlogging tolerance of Zelkova schneideriana’ and combined with the membership function,the correlation analysis and principal component analysis to evaluate drought and waterlogging tolerance of experimental materials.The results are as follows:1.With the intensification of drought stress and the persistence of stress time,the plant height growth rate of Zelkova schneideriana was slowed down,and drought injury index gradually increased.Simultaneously,at the beginning of stress,the Rec and MDA content increased slowly,resulting in damages of cell membrane structure and function.The osmoregulatory substances such as SS and Pro contents began to rise,and then the POD and SOD activities increased,while the leaf Chl content increased.With the intensification of drought stress and the persistence of stress time,Zelkova schneideriana suffered more damage,POD and SOD activities decreased,WSD,MDA content and Rec increased sharply,leaf Chl content decreased sharply,and the effects of regulating osmotic pressure by increasing the SS and Pro contents gradually diminishes.2.With the prolonged waterlgging stress time,the inhibitory effects on the plant height growth of Zelkova schneideriana increased gradually,and injury index also gradually increased.There is a certain difference between varieties Meanwhile,at the beginning of stress,the Rec and MDA content increased slowly,leading to damages on cell membrane structure and function.SS and Pro contents began to rise,and then the POD and SOD activities increased while leaf Chl content increased.With the prolongation of waterlgging stress time,the injury of Zelkova schneideriana increased gradually,the activities of POD and SOD decreased,the WSD,MDA content and Rec continued to rise,the content of Chl in leaves declined sharply,and the contents of SS and Pro continued to rise to adjust cell osmotic pressure.3.Combined with the results of correlation and principal component analysis,five evaluation indexes that can be used as the drought tolerance of Zelkova schneideriana were found,including drought injury index,Rec,MDA content,SOD activity and WSD.4.On the basis of the results of correlation and principal component analysis,six evaluation indexes that can be used as the waterlogging tolerance of Zelkova schneideriana were identified,including the waterlogging injury index,Rec,Pro content,SOD activity,Chl content and WSD.5.According to the value of the membership function and comprehensive indexes under drought stress,the order of the drought tolerance is:’Hentiangao’(value of membership function is 0.667,comprehensive index is 0.695),’Linyuan’(0.664,0.694),’Xingfu’(0.650,0.680).6.Based on the value of the membership function and comprehensive indexes under waterlogging stress,the order of the waterlogging tolerance is:’Hentiangao’(value of membership function is 0.473,comprehensive index is 0.490),’Xingfu’(0.459,0.477),’Linyuan’(0.448,0.470). |
