Comparative Study On Heat Resistance And Cold Resistance Of Three Species Of Chaenomeles

Chaenomeles is a deciduous small tree or shrub with various shapes,beautiful flowers,and gorgeous colors.It is also an important tree species in landscaping.When the temperature exceeds its growth and adaptation range,it will seriously affect the ornamental and ecological effects,which will lead to death when it is serious.To provide theoretical basis and guidance for determining the high-temperature and low-temperature bearing capacity of Chaenomeles,and for the maintenance and management and breeding of new varieties with heat resistance and cold resistance,the eight-year-old plants of Chaenomeles sinensis(Thouin)Koehne,Chaenomeles speciosa Toyo Nishiki,and Chaenomeles japonica Da Fugui were used.In natural summer between mid-May and mid-September,the relative conductivities of stems and leaves,proline,soluble protein,soluble sugar,starch and water content of stems were measured.During the natural overwintering period from mid-September to mid-January,the relative conductivity of stems and six physiological and biochemical indicators of Superoxide dismutase(SOD),Peroxidase(POD),soluble sugar,starch and water contents were measured.For both heat resistance and cold resistance studies,the semi-lethal temperature was fitted by combining the conductivity with logistic equation,and the correlation analysis of various indicators and heat resistance as well as cold resistance was made,and the subordinate mean value was calculated using the subordinate function method,and the heat resistance and cold resistance were comprehensively evaluated.The main results are as follows:1.Study on heat resistance:(1)With the increase of air temperature,the heat resistance in stems of all three species showed a trend of gradual enhancement.In July and August,the semi-lethal temperature reached the maximum values,which were 46.88 ? for Chaenomeles sinensis(Thouin)Koehne,50.20 ? for Chaenomeles speciosa Toyo Nishiki and 46.45 ? for Chaenomeles japonica Da Fugui.(2)During the research period of heat resistance,various physiological indicators in stems showed regular changes.With the increase of ambient temperature,proline contentand water content increased with the increase of heat temperatures,which was consistent with the change trend of heat resistance.Soluble sugar content and starch content decreased with the increase of heat temperatures,which was opposite to the change trend of heat resistance.(3)The function value of each index was calculated by membership function method to comprehensively evaluate the heat resistance.The results showed that the heat resistance in stems ranked as Chaenomeles speciosa Toyo Nishiki > Chaenomeles sinensis(Thouin)Koehne > Chaenomeles japonica Da Fugui.2.Study on cold resistance:(1)With the decrease of air temperature,the cold resistance in stems of Chaenomeles speciosa Toyo Nishiki and Chaenomeles japonicas Da Fugui reached the maximum level in December,at-32.83 ? and-29.9 ? respectively,with a difference of 3 ?.In January,the cold resistance of Chaenomeles sinensis(Thouin)Koehne in stems reached the strongest,which was-33.33 ?.(2)Soluble sugar content,SOD and POD activity of stems in three species increased with the increase of cold resistance during cold hardening,which was consistent with the change trend of cold resistance.(3)Under comprehensively evaluating the cold resistance of three species using the membership function method,the results showed that the order of cold resistance in stems was Chaenomeles sinensis(Thouin)Koehne > Chaenomeles speciosa Toyo Nishiki >Chaenomeles japonica Da Fugui.