Study On Adaptability Of Morphological And Physiological Of White Clover Under Low Temperature Stress

Turf is as an important symbol of modernization cities along with the process of civilization and to improve the quality of the environment and further to develop continually in the world. As turf has the fanctions of freshing air, preventing pollutionion to environmental n, and soil and water conservation ect. Turf basic research has been given great attention to its management, breeding in the world. Trifolium repens L. is a perennial cool-season turfgrasse, originated in the eastern Mediterranean region. Sichuan, Guizhou, Yunnan, Guangxi, Heilongjiang, and other places in Chana has many wild species distribution.Trifolium repens L. has many excellent atrbutes of growing fast, strong prapergation ability ,tolerant tread and easy to management that made it widely used in residential areas, street greening and so on.. But in the north of China, low temperatures restricted the growing of turf. In order to improve the freezing-tolerance of turf, many work has been on the adapability to the environment for introduced cultivars, because many Trifolium repens L. cultivars were used introduced from abroad in our country. In order to solve the problem with low temperature, we should study its adaptability and coldness resistant mechanism and reveal its characters adapting to the low temperatures by morphological, physiological and molecular techniques. It's important for further improving turf quality and breeding of native plants and applying in production.In this study, 4 Trifolium repens L. cultivars were used with different growth characters through field experiment, pot experiment and artificial cold conditions experiment by morphological physiological and Molecular Biology techniques to seek for different cultivars'adaptability under cold stress and the mechanism of cold resistant. The results were :1. 4 TrifoliumrepensL of epidermal cells and the CTR(%) of different species were: Koola > Prop > Rivendel > Mini Blackdragon and the density of stomata of Mini Blackdragon was much denser than others. The vein protuberant degree and SR(%) of different species were: Mini Black gragon > Rivendel > Prop > Koola. Mini Blackdragon in the growth characteristics is better than the others and has the advantages of cold hardiness.2. The xylem ratio of the the structure of stemstock and root in different species of Trifolium repens L.were: Mini Blackdragon < Rivendel< Prop< Koola. The cortex rotio of the the structure of stemstock and root in different cultivars were: Mini Blackdragon < Rivendel < Prop < Koola. And the vessel diameter of the the structure of root in different cultivars were: Mini Blackdragon < Rivendel< Prop< Koola.3. Mini Blackdragon had the lowest membrane permeability and the strongest cold resistance among 4 species, the membrane permeability of Rivendel was lower than Prop and Koola. had the highest membrane permeability and the smallest cold resistance among 4 species. The accumulations of MDA were earlier than the additions of membrane permeability.4.The chlorophyll content of Mini Blackdragon was higher than other species and the abilities of retaining water of Mini Blackdragon was the best, Rivendel had the better abilities of retaining water than Prop and Koola.was the worst. The free proline accumulation of Mini Blackdragon was much higher than other species. With the lower temperatures, Soluble sugar content of Mini Blackdragon added continuously and its accumulation was higher than other species. Soluble protein content of Mini Blackdragon was higher than other 3 species all long, either was the SOD and POD activities of Mini Blackdragon. Thus it showed that Mini Blackdragon had better ability of cold resistance.5. By RT-PCR technology , Mini Blackdragon under the low temperature clone a gene CBF3(303 bp).