Study On Heat And Shade Resistance Of Introduced Early Large-flowered Group Clematis In Shanghai

With the developments of city greening and the increasing demand for climbing plants,the scientists have focused on early large-flowered group Clematis,which have highly ornamental value climbing plants with long flowering periods,large flower diameters and rich colors.Therefore,it's significant to introduce early large-flowered group Clematis,and to select suitable cultivars in Shanghai.Phenological of fourteen Clematis cultivars,heat resistance and shade studies of 4 Clematis cultivars were observed respectively,and the evaluation index of heat resistance were selected to explore the effects of shade treatment on growth.The main results are as follows:(1)The introduction of 14 cultivars of early large-flowered group Clematis cultivars in Shanghai area are of high ornamental value,the florescence can lasts from mid April to late June.The florescence of most cultivars can be maintained in 20~30 d,and ‘Ice Blue' has the longest florescence of 48 d.(2)‘Seraphina','Gillian blades',‘Zotemp' and ‘Mrs George Jackman' had strong resistant ability,with the lowest wilt rate of 13%.‘Red Star',‘Angela',‘Ice Blue',‘Little Mermaid',‘The President',Kaiser' and ‘Sunset' were susceptible,the highest wilt rate reached 80%.According to the selected cultivars with strong resistance,it can provide reference for introduction and hybrid breeding.(3)Combined with field growth status and high semi-lethal temperature,the effects of high temperature treatments of 40 ? /32 ?(day/night)in artificial chamber on the morphology,heat injury index,relative water content(RWC),cell membrane integrity,soluble sugar contents and the activities of antioxidant enzymes of 4 early large-flowered group Clematis cultivars such as ‘Kaiser',‘Zotemp',‘Sunset' and ‘Meng' were investigated in Shanghai.The results indicated that 4 cultivars showed different degrees of damage symptom such as the leaves curled and withered under high temperature for 6 days.Heat injury index,MDA contents,soluble sugar contents and REC increased significantly,whereas RWC decreased.Morever,POD and CAT activities also rised,SOD activity increased at the beginning and then decreased to the initial levels in the end.The correlation analysis showed a significantly positive correlation between REC,CAT and heat injury index,so that REC might be used as an efficient index to rapidly evaluate heat resistance of Clematis.The comprehensive values of the heat resistance of ‘Kaiser',‘Zotemp',‘Sunset' and ‘Meng' were 0.4766,0.5308,0.5398 and 0.5824 respectively,high temperatures resistence of ‘Meng' is the strongest in four cultivars,while ‘emperor' is the weakest,which was consistent with the result of heat injury index,REC and other physiological indicators.At the same time,high semi-lethal temperature can not be used to evaluate the heat resistance.These results should provide an important theoretical basis for the introduction and cultivation,the selection of hybrid parents for the early large-flowered group Clematis in Shanghai area.(4)The light compensation point and light saturation point can finely reflect the photosynthetic capacity of different cultivars of Clematis.‘Gillian blades' and ‘The Vagabond' have better ability to adapt strong light,‘Mrs George Jackman' is weaker,and ‘Seraphina' is the weakest.‘Mrs George Jackman' and ‘Seraphina ' are more suitable for shading.Chlorophyll fluorescence parameters are effective indexes to identify photosynthetic performance and resistence ability of Clematis cultivars,and higher Fv/Fm and ?PS? values are basis of high photosynthetic efficiency.