Comparison Study On The Cold Resistance Of Three Michelia Platypetala Under Different Low Temperature Stress

In order to compare the cold resistance of different cultivars and the physiological response of Michelia platypetala to low temperature stress,We compared the cold resistance of three Michelia platypetala cultivars by field observation,morphological index determination and physiological index determination under three different low temperature stress.In order to provide basis for the popularization and application of varieties,and to screen out the corresponding physiological indexes of different low temperature stress ways.The main results are as follows:(1)The morphological characteristic indexes related to cold resistance mainly include flower bud node spacing,leaf size,surface wavy size and branch number.(2)Under natural low temperature stress,RWC and REC of three Michelia platypetala increased with the decrease of temperature.MDA content first increased and then decreased with the decrease of temperature.With the decrease of temperature,the content of Chl first remained unchanged and then decreased.The contents of SP,SS and Pro increased with the decrease of temperature.POD activity first decreased and then increased with the decrease of temperature.There was almost no change in SOD activity.(3)Under artificial slow low temperature stress,REC of three species of Michelia platypetala increased with the decrease of temperature.SP content first increased and then decreased with the decrease of temperature.SS content first decreased and then increased with the decrease of temperature.The content of Pro decreased first and then increased with the decrease of temperature.POD activity decreased with the decrease of temperature.There is no obvious regularity in other indexes.(4)Under the condition of artificial fast low temperature stress,the cell solution concentration was changed by adjusting the tissue water content to adapt to the changing environment temperature.The RWC of three kinds of Michelia latifolia decreased with the decrease of temperature.Rec increases with the decrease of temperature.MDA is the product of membrane lipid peroxidation.Low temperature destroys the cell membrane and produces MDA.In the process of low temperature adaptation,MDA will be gradually removed,and its content will increase first and then decrease with the decrease of temperature.The Chl content first increased and then decreased with the decrease of temperature.It is speculated that the chloroplast will be destroyed when the low temperature reaches a certain degree.SP content decreased with the decrease of temperature.SS content increased with the decrease of temperature.The content of Pro decreased first and then increased with the decrease of temperature.It is suggested that SS and pro play other roles in plant cold resistance besides being osmotic regulators.The accumulation of peroxides and superoxides was obvious under rapid cooling.POD activity decreased with the decrease of temperature.The activity of SOD decreased first and then increased with the decrease of temperature.(5)Through the comprehensive analysis of the cold resistance of each index under three different stress modes,the semi lethal temperature result of the relative conductivity fitting out of the two artificial low temperature stress treatments,and the observation of the plant morphology and flowering dynamics,the cold resistance ranking of three Michelia platypetala can be carried out: Kuoban > Fenyun >Hongyan.(6)Different stress methods have their own advantages and limitations: in this study,we found that the data obtained from natural low temperature stress and artificial fast low temperature stress are more valuable.(7)According to the principal component analysis,there are five indexes related to acclimation cold resistance of Michelia platypetala: REC,SP,SS,Pro and POD.There are 9 indexes related to stress and cold resistance of Michelia platypetala: RWC,REC,MDA,Chl,SP,SS,Pro,POD and SOD.According to the data analysis results of three different stress modes,the 9 indexes are all related to the cold resistance of plants,which are suitable for the cold resistance physiological research of Michelia platypetala.