The Study On Comprehensive Evaluation Of Heat-tolerance And Heat-tolerant Mechanism In Summer Chrysanthemum

Chrysanthemum is a traditional famous flower in China,as a cut flower,pot plants and an ornamental plant fred its wide use in gardens.In present study,physiological and biochemical indicators,anatomical structure,photosynthetic characteristics under high temperature of summer were studied in five cultivars of 'Fenhe','Huoju','Zihe','Jinxing','Jinguang'.Membership function was used to evaluate the blooming traits,and relevant analysis was used to analyze relationships between physiological and biochemical indicators,the anatomical structure and blooming traits.In order to establish the heat resistance evaluation system of chrysanthemum,heat resistance indexes were searched by correlation analysis,main component analysis,regression analysis.The main results are as follows:(1) Blooming duration of single inflorescence and whole plantlet in 'Fenghe','Zihe' and 'Huoju' were longer than 'Jingxing' and 'Jingguang',while lower rate of blind flower and higher rate of maximum blooming was observed in the former three cultivars.The subordinate function values analysis showed that the blooming characteristics were decreased in 'Fenghe','Huoju','Zihe','Jingxing' and 'Jingguang' in turn.(2)Under high temperature in summer,the CAT and POD activity and the content of MDA in leaves are significant correlation with flowering ability,which can be used as important heat resistance indicators.(3) The correlation between thickness of leaf and palisade tissue,and thickness of spongy tissue were observed,but there was no correlation between the thickness of leaf and heat tolerance,it inferred these indicators can't be used as heat resistance indicators.Palisade tissue against spongy tissue and SR were closely related to flowering ability,which can be used as heat tolerance indicators.Positive correlation between the Palisade/spongy and flowering ability,while negative correlation between SR and flowering ability,were observed.(4) Photosynthetic rate changes of 'Fenhe' showed single-peak curve,while that in 'Zihe','Huoju', 'Jinxing' and 'Jinguang' showed the double-peak curve.The correlation between Chla,Chl(a+b) and diurnal integral value of Pn were observed,the correlation coefficient are 0.908 and 0.891,respectively. Highest light saturation point amounting to 1500μmol·m^-2·s^-1 in 'Zihe',while lowest value amounting to 1320μmol·m^-2·s^-1.in 'Jinguang' were detected.The light compensation point of was lowest in 'Fenhe'(100μmol·m^-2·s^-1),while it was highest in 'Jinguang'(135μmol·m^-2·s^-1).(5) Four out of 12 parameters,i.e.,rate of blind flower(X₃),SR of leaf(X₆),MDA content in leaf (X₉) and daily net photosynthetic accumulation(X₁₂),were screened as heat tolerance indexes by main component analysis and correlation analysis.Heat resistance evaluation system was established based on these four indexes.The evaluation model formula isVP=-1.754-0.002X₃-0.000019X₆+0.001X₉+0.025X₁₂. In terms of value of the comprehensive evaluation(D),the decrease of heat tolerance of five cultivars was 'Huoju','Zihe','Fenhe','Jinguang' and 'Jinxing' in turn.And significant correlation between predictive value(VP) and the comprehensive evaluation value(D) was observed.