Evaluation Of Cold Resistance And Physiological Responses To Low Temperature On Three Cultivars Of Cattleya Hybrid

Cattleya hybrid,which has important ornamental value and enjoys the reputation of king of tropical orchids in the world,belongs to Cattleya genus of Orchidaceae family.The temperature has always been an important factor affecting its growth and consumption.It is of great significance to study the physiological response and cold resistance evaluation of Cattleya varieties under low temperature stress for its cultivation and breeding.In this study,Sophrolaeliocattleya Doris and Byron ‘Christmas rose’,Cattleya(Chien Ya Ruby x Mini Purple)’Forever Red’ apple’ and Rhyncattleanthe younn-min Orange ’Golden Satisfaction’were used as materials to measure chlorophyll fluorescence parameters and biochemical indicators of leaves under different low temperature.The physiological responses to low temperature of three cultivars were studied and the cold resistance was comprehensively evaluated by membership function method.The main results are as follows:(1)Under the stress of low temperature,the chlorophyll content of Sophrolaeliocattleya Doris and Byron ‘Christmas rose’ decreased,which was significantly lower than CK,and the difference between different stress of low temperatures was not significant.The chlorophyll content of Cattleya(Chien Ya Ruby x Mini Purple)’Forever Red’ increased significantly under low temperature stress at 15 ℃ and 5 ℃ while decreased under low temperature stress at 10 ℃ with insignificantly.The chlorophyll content of Rhyncattleanthe Young-Min Orange ‘Golden Satisfaction’ changed differently under different stress of low temperatures.The chlorophyll content was significantly different between different stress of low temperatures and different Cattleya varieties.Overall,the chlorophyll a/b value increased gradually with the decrease of stress temperature.(2)Under the stress of low temperatures,Fv/Fm and Y(II)of three Cattleya cultivars decreased significantly,qP had no obvious change regulation,Fv/Fm had significant difference between different stress temperatures.The NPQ of Sophrolaeliocattleya Doris and Byron‘Christmas rose’ decreased continuously.The NPQ of Cattleya(Chien Ya Ruby x Mini Purple)’Forever Red’ and Rhyncattleanthe Young-Min Orange ‘Golden Satisfaction’ increased first and then decreased.The significant difference of Y(II)、 qP and NPQ between different stress temperatures varied from species to species.Under low temperature stress at 15 ℃ and 10 ℃,the Fv/Fm,Y(II),NPQ and qP of Cattleya(Chien Ya Ruby x Mini Purple)’Forever Red’ were significantly lower than Sophrolaeliocattleya Doris and Byron ‘Christmas rose’.Under 5 ℃ low temperature stress,the significant difference of different indicators between different Cattleya varieties are different.(3)Under the stress of low temperatures,the contents of REC and Pro of three cultivars of Cattleya hybrid increased gradually with the decrease of temperature.Under low temperature stress at 15 ℃,the REC of Rhyncattleanthe Young-Min Orange ‘Golden Satisfaction’ was significantly lower than that of CK.The MDA contents of Sophrolaeliocattleya Doris and Byron ‘Christmas rose’ and Cattleya(Chien Ya Ruby x Mini Purple)’Forever Red’ were extremely significant declined.Under low temperature stresses of 10 ℃ and 5 ℃,the REC value and MDA content in three Cattleya varieties increased significantly.There were significant differences in REC value and MDA contents among different stress temperatures.The significant differences of REC value and MDA contents were varied from different low temperatures among different Cattleya varieties.(4)Under low temperature stress,different Cattleya varieties have different osmotic adjustment mechanisms.The content of Pro and SP in Sophrolaeliocattleya Doris and Byron ‘Christmas rose’ increased,while SS and AA content decreased.The content of SS and AA in Cattleya(Chien Ya Ruby x Mini Purple)’Forever Red’ increased and the content of Pro decreased while the content of SP decreased first and then increased.The Pro,SS,SP and AA of Rhyncattleanthe Young-Min Orange ‘Golden Satisfaction’ decreased at 15 ℃ low temperatures stress and the contents of SS,SP and AA increased under low temperature stress at 10 ℃ and5 ℃ while the content of Pro decreased.There were significantdifferences in Pro,SS and SP contents between different stress temperatures,while the difference of AA content was not significant.The content of SS(10 ℃ and 5 ℃),SP and AA were significantly different among different Cattleya varieties while the difference of Pro content was not significant.(5)Under low temperature stress,the activity of SOD,POD and CAT in Sophrolaeliocattleya Doris and Byron ‘Christmas rose’ showed a downward trend.The activity of SOD in Cattleya(Chien Ya Ruby x Mini Purple)’Forever Red’ decreased under low temperature stress and the activity of POD and CAT increased in general,while the activity of CAT decreased significantly at 15 ℃.The activity of POD in Rhyncattleanthe Young-Min Orange ‘Golden Satisfaction’ was significantly increased under low temperature stress,the activity of SOD was only significant increasing under low temperature stress at 5 ℃ and the activity of CAT was only increased under low temperature stress at 15 ℃.The activities of SOD,POD and CAT were significantly different between different stress temperatures.The difference of SOD activity between different Cattleya varieties was small while the activities of POD and CAT were significantly different.(6)Correlation analysis results show that there is a certain correlation between each cold resistance index.Principal component analysis extracted a total of 2 principal components,whose cumulative contribution rate is up to 100%,which can represent the comprehensive situation of the cold resistance of the three Cattleya varieties.Among them,the first main component comprises chlorophyll content,Fv/Fm,Y(II),NPQ,MDA,Pro,SS,SP,SOD and POD,whose characteristic value is 8.478 and contribution rate is 65.21%.The second principal component contains qP,REC and CAT.with a eigenvalue of 4.522 and a contribution rate of 34.78%.By comprehensive correlation analysis and principal component analysis,it was concluded that Y(II),Pro content,SP content and POD enzyme activity can be selected as the identification index of Cattleya varieties’ cold resistance.According to the comprehensive evaluation score of membership function method,the cold resistance of three Cattleya cultivars was ranked as follows: Cattleya(Chien Ya Ruby x Mini Purple)’Forever Red’ > Rhyncattleanthe Young-Min Orange ‘Golden Satisfaction’ > Sophrolaeliocattleya Doris and Byron ‘Christmas rose’,whose comprehensive evaluation value of cold resistance value(D value)was 0.907,0.652,and 0.138,respectively.