Study On Evaluation Of Introducted Osmanthus Fragrans And Its Physiology-biochemistry Of Cold Hardiness In Beijing

Due to the geographical, climatic and other conditions, the main garden trees are deciduous trees and the urban landscape lacks vibrant green duing the winter in Beijing. To change this situation, rich urban color, it is a great cause to introduce species of evergreen trees. Osmanthus fragrans is good evergreen garden trees and economic trees that is native to southern China, making the environment green, landscape and full of fragrance, but it's few in Beijing. Through the investigation and selection of Osmanthus fragrans resources, four different introduced Osmanthus frgrans were cultivated and acclimated, and on this basis, the cold physiological and biochemical research and the chlorophyll fluorescence kinetics were carried out. Here is the list of the major research advances:1. Through the monitor of winter survival rate of Osmanthus fragrans introduced from Jiangsu and the survey of the northern parts of resoueces by five regions, it's found that, due to difference suitable environment, the southern Osmanthus fragrans is not suitable for immediate introduction to plant in Beijing, and grafts of the local resource-rich northern region are the preferred seedings. According to data collected and field survey, few resoueces of Osmanthus fragrans are safe in latitude 39°～41°as Beijing, Tianjin and other areas without any protective measures during the winter but the resource of latitude 35°～37°as Xinxiang, Linyi etc is rich that can be a major introduced source of the north.2. Based on the investigation and cultivation test, we established a relatively complete introduction, domestication and cultivation propagation technique system of Osmanthus fragrans, including introduction and preliminary screening, transplanting transportation, maintenance management, and other winter acclimation. Four Osmanthus fragrans varieties were successfully introduced from Linyi and Xinxiang:O.fragrans'Shan Yingui', O.fragrans 'Huangchuan Jingui', O.fragrans 'Zhusha Dangui'and O.fragrans 'Zao Yingui'. In the study of grafting technique, we found that rootstock, scion and the grafting time would affect the graft survival rate. Using fringed with a two-year strdents as rootstock seedings, selecting nutritionally adequate buds full of scion and in April, the graft survival rate will be higher.3. Simulating natural temperature conditions, measuring a variety of physiological and biochemical indicators of Osmanthus fragrans, and combined with the principal component analysis, we made an evaluation of the cold resistance of Osmanthus fragrans and obtained the cold resistance of them. It is showed that:O.fragrans'Shan Yingui'>O.fragrans'Huangchuan Jingui'>O.fragrans'Zhusha Dangui'>O.fragrans'Zao Yingui'. In the selected nine indicators, the soluble protein, membrane permeability, and antioxidant enzyme activities are reliable indicators of cold hardiness in response to better cold tolerance among different species of Osmanthus fragrans.4. In the study of cold resistance induction of Osmanthus fragrans, we found that exogenousing plant growth retardants can inhibit excessive growth of Osmanthus fragrans fall slightly, promote branch lignification, improve the cold tolerance of Osmanthus fragrans. The optimal concentration of exogenous PP333 is 1500-2000mg/L; CCC appropriate concentration is 500-1000mg/L; The effect of exogenous ABA is scarce.5. Duing the winter of chlorophyll fluorescence kinetics study, it's found that:First, Fv/Fm and Fo increased with the decrease of temperature, indicating in the course of the winter, light-harvesting antenna systems had been damaged and then inhibited the original reaction of photosynthesis; Second, the qP of Osmanthus fragrans was always high, indicating that PSII reaction center maintain a high degree of openness in the winter, thus reducing the damage to PSII reaction center by the lateral accumulation in PSII of the excitation energy. Electron transferred by PSII is possible consumed through Mehler reaction or cyclic electron transport and other non-linear ways of electron transferring; Third, NPQ reduced with the decreasing of temperature,and NPQ was closed with the antenna system heat dissipation. So it can be deduced, Osmanthus fragrans mainly resist winter cold stress through PSII reaction center or proton gradient heat dissipation but not antenna system.