Preliminary Study On Response Mechanism Of Hydrangea Macrophylla ’Bailmer’ Leaves To Different Temperatures

Hydrangea has various colors.As a popular potted flower,It is well received in the market in recent years.In this study,the effects of different temperature treatments on growth,physiological effects,photosynthetic characteristics,endogenous hormone content and flowering gene expression of Hydrangea ’bailmer’ were studied.The response mechanism of Hydrangea under different temperatures was preliminarily explored,which provided a scientific basis for the cultivation and landscape application of Hydrangea.The main results are as follows:1.At CK 25℃,the growth and flowering quality of Hydrangea was the highest.When treated at 17℃ for 60 days,the leaves grew slowly and fallen leaves appeared.In addition,when the relative high temperature is 30℃,the leaves appear serious scorched leaf phenomenon.It indicated that the growth of Hydrangea could be inhibited by long-term low or high temperature.2.From the measured values,REC,SS,APX and CAT had the lowest values at 17℃.At CK 25℃,the lowest physiological indexes were Pro and AA.At 30 ℃,MDA,SP,SOD and POD were the lowest.3.At 17℃,Chlorophyll a,Chlorophyll b,Chlorophyll a+b,Chlorophyll a/b,Carotenoids,Rubisco enzyme activity,Pn,Ci,Tr,Gs,Fo,Fm,Fv,Fs,Fv/Fm,Fv/Fo and Phi 2 had the lowest values.At CK 25℃,the lowest physiological indexes were Drate,PhiNPQ,qN,NPQ and qL.At 30℃,WUE,Prate,E,ETR,Lpfd,Fv,(φPS Ⅱ,PhiNO,SPAD,PAR and qP were the lowest.There was a positive correlation between SPAD value and Chlorophyll content(Chl a,Chl b,CT,Chla/b and Car).But the fitting degree with Chlorophyll a/b is not high.4.The lowest values of IAA,GA3,ZR,SA and ABA/GA3 appeared at 17℃.At 30℃,ABA,JA,IAA/ABA and IAA+GA3+ZR/ABA were the lowest.5.Through the correlation analysis of each index of "Bailmer" under different temperature treatment,and further principal component analysis,the results of plant height,stem diameter,crown width,leaf length,leaf width,leaf thickness,leaf number,SP,Fv,SS,CAT,APX,ABA/GA3,JA,Gs,Fo,Fs,MDA,Drate,Prate,Ci,Pn,REC,POD,SOD,Chlorophyll a/b,qP,Pro,Lpfd,qL,PhiNPQ 31 index information,extracted 5 principal components as new variables to replace the original 59 variables.The results showed that plant height,stem diameter,crown width,leaf length,leaf width,leaf thickness,leaf number,SP,Fv,SS,CAT,APX,ABA/GA3,JA,Gs,Fo,Fs,MDA,Drate,Prate,Ci and Pn could be used as evaluation indexes under temperature response.6.Relative low temperature 17℃ and 25℃ showed a rising trend,but the increase was most significant at 25℃ for 30 days.When the relative high temperature is 30℃,it firstly increases and then decreases.In addition,the effect of relative low temperature on FT gene expression was greater than that of relative high temperature.The expression of FT gene was the lowest at 30℃.