Study On The Mechanism Of Different Varieties Of Herbaceous Peony (Paeonia Lactiflora Pall.) In Response To Waterlogging Stress

To investigate the response and recovery characteristics of different Paeonia lactiflora Pall.varieties under waterlogging stress,six herbaceous peony varieties‘Lihong'‘Dafugui'‘Hongxiuqiu'‘Qihualushuang'‘Taohuafeixue'‘Yangfeichuyu'with high ornamental value,which were mainly grown on production,were used as experimental materials.After the vegetative growth of each variety was completed,the field simulated waterlogging stress experiment was carried out by the semi-water flooding pot method.Analysis of photosynthetic parameters,chlorophyll fluorescence parameters,relative leaf water content(RWC),relative electrical conductivity(REC),chlorophyll content,lutein cycle and leaf microstructure Change,and comprehensively compare the water tolerance of various varieties with these indicators.According to the results of comparison of waterlogging tolerance,three varieties with strong water tolerance,medium and weak were tested for changes in antioxidant enzyme activity,malondialdehyde(MDA)content,soluble protein content,soluble sugar content,endogenous polyamines and hormone content.And observe the changes of root microstructure by paraffin section method.Further study the response of endogenous hormones,polyamines and antioxidant enzyme systems to different waterlogging tolerance peony varieties to waterlogging stress.The result shows that:(1)After waterlogging stress,the leaves of various varieties of Paeonia lactiflora turned red or yellow,the microstructure changed,the relative electrical conductivity of the leaves increased,the chlorophyll content was significantly reduced,and the function of mesophyll cells was impaired,resulting in a significant decrease in the net photosynthetic rate Pn and a maximum photochemical Yield Fv/Fm is also significantly reduced,and the photosynthetic capacity of the leaves is impaired.At this time,the plant can consume excess light energy by increasing heat dissipation by increasing the heat dissipation coefficient NPQ and the xanthophyll cycle.After the stress was relieved,all indicators recovered to varying degrees.(2)According to the comprehensive analysis of 15 indicators such as RWC,REC,Pn and Fv/Fm,the optimal regression equation is established:D=(95.356-16.534X₁+7.706X₂+0.501X₃+10.952X₄+1.623X₅)×10^-3,where X₁,X₂,X₃,X₄,and X₅represent the waterlogging resistance coefficients using RWC,REC,q P,Chla/b,and WUE as indicators.The waterlogging resistance of the experimental materials followed the pattern:‘Lihong'>‘Yangfeichuyu'>‘Taohuafeixue'>‘Dafugui'>‘Hongxiuqiu'>‘Qihualushuang'.Among them,60%of the leaves of‘Lihong'with strong waterlogging tolerance and‘Dafugui'with medium waterlogging tolerance experienced longer stress time,and they have higher chlorophyll content and relative leaf water content under waterlogging stress,and they can maintain a high net photosynthetic rate at the initial stage of stress for normal plant growth.Varieties with high waterlogging tolerance when photosynthetic capacity is suppressed can better consume excess light energy through lutein cycle and heat dissipation.(3)Through further comparison of three varieties of‘Lihong'with strong comprehensive waterlogging resistance,‘Dafugui'with medium comprehensive waterlogging resistance and‘Qihualushuang'with weak comprehensive waterlogging resistance.Varieties with comprehensive waterlogging tolerance can accumulate more nutrients during stress,generate more aeration tissue at the root,improve antioxidant enzyme activity,increase the accumulation and utilization of soluble proteins and soluble sugars,increase putrescine(Put)and accumulation of spermine(Spm)content,increase auxin(IAA),gibberellin(GA₃),zeatin(ZT)and salicylic acid(SA)content,reduce ABA content to adapt to waterlogging stress.The increase of IAA,GA₃,ZT content can help recovery after injury caused by peony stress.This can provide new ideas and reference basis for the cultivation of new varieties of paeonia tolerant to waterlogging and the regulation of improvement of waterlogging tolerance in production,and then based on production needs,a comprehensive control plan for improving the waterlogging resistance of paeonia lactiflora can be formulated.The purpose of this paper is to analyze the different responses of different peony species under waterlogging stress by simulating waterlogging stress,it provides new ideas and reference basis for the selection and breeding of water-resistant varieties,the realization of comprehensive control of high-yield cultivation of peony and waterlogging resistance in production.In the later period,it is still necessary to further expand the number of varieties,combined with in-depth research on resistance genes related to waterlogging resistance,to provide theoretical references for the breeding and production of new waterlogging resistance varieties.