| Rhododendron is a very famous ornamental plant in the world.The color and the shape of the flowers are beautiful.Besides,the leaves of Rhododendron are worth to enjoy.It can beautity our family during the Spring Festival.Rhododendron is one of ten traditional famous flowers in China,with its reputation as the "flower of xi shi",so it is a very good garden plant with high ornamental value and medicinal value.In addition,our country is rich in all kinds of Rhododendron resources,and a treasure trove of Rhododendron in the world,which provide the possibility for the wide application of Rhododendron.But Rhododendron will stop growing when temperature is lower,so cold hardiness become the key limiting factors of the landscape application of the Rhododendron.While the study on the effects of exogenous substances to enhance Rhododendron cold resistance are rare.In order to solve the above problems,20 Rhododendron cultivars were used as the test materials,which cold resistance was evaluated by measuringsoluble sugar content,soluble protein content,malondialdehyde(MDA)content of leaves,hydrogen peroxide(H2O2)content,peroxidase(POD)activity,and superoxide dismutase(SOD)activity,and the growth morphology.The method of subordinate function,comprehensive evaluation on the cold resistance of different Rhododendron cultivars was made.A Rhododendron ‘Zhuang Yuan Hong' that is less resistant to cold was choosed to analysis 8 physiological indicators,4 photosynthetic indexes and 11 leaf anatomical structure indexes of Rhododendron after spraying 0,5,10,20,30 mg/L ABA.The results showed that:(1)Using the method of subordinate function weights coefficient of standard deviation,the cold resistence capacity of 20 Rhododendron cultivars was comprehensively evaluated,the cold resistance ability of R.‘Hong Yue' was the best among 20 Rhododendron cultivars under natural low temperature stress(the low temperature to-8 ?,the most high temperature to 13 ?)for 20 days.The synthetic evaluation and correlation analysis was carried out for the physiological indexes of cold resistance.Correlation analysis results showed that the soluble sugar and the subordinate function of hardiness in moderate positive correlation,and the integrated evaluation was positively related to SOD activity,POD activity was positively correlated,but the content of MDA was in moderate negative correlation,andH2O2 content and soluble protein content were negatively correlated.Through a combination of morphological observation,comprehensive evaluation and correlation analysis,the membership function of 20 Rhododendron cultivars order of hardiness was found.(2)R.‘Zhuang Yuan Hong' is one of Rhododendron cultivars which is less resistant to cold,among 20 Rhododendron cultivars.After spraying 0,5,10,20,30 mg·L-1 ABA,it was found that soluble sugar content,MDA content,POD activity and SOD activity after low temperature stress for 5 days was higher than those after low temperature stress for 0 days,the relative conductivity increase was lesser,and H2O2 content lowered after the first.After spraying 10 mg·L-1 ABA,the change of relative electrical conductivity,soluble sugar,Pro,soluble protein change was the most significant,while the MDA content,POD activity,SOD activity,H2O2 content change has no obvious difference.Stomatal opening smaller(AS),intercellular CO2 concentration(Ci)decrease,net photosynthetic rate(Pn)and transpiration rate(Tr)enhance.Applied 10mg·L-1 ABA had the biggest influence in the photosynthesis indexs of Rhododendron.By analysizing 11 anatomical structure indexes of R.‘Zhuang Yuan Hong',after spraying different concentration of ABA,TP,TS and TL of R.‘Zhuang Yuan Hong' increased,but no uniformity between the concentration change.At last,Clustering analysis was carried out by 11 anatomical structure indexes,the result was divided into three categories,gate thickness ratio(P/S),stomata density(DS),leaf thickness(TV)were the representative indexes respectively among all kinds of anatomical structure indexes.Comprehensive hardiness physiology index,photosynthetic gas exchange parameters and anatomical structure indexes characteristics,it could be obtained that ABA can obviously improve the cold resistance of R.‘Zhuang Yuan Hong' under low temperature stress. |
PDF Full Text Request