Study On The Molecular Mechanism In Alpine Plant Response To Cold-stress And UV-B Radiation Stress

Aiming at the current steppe in the northwest of Sichuan facing the serious degeneration even the threat of desertification, the revegetation experiments were conducted on the northwest plateau sandback of Sichuan, and various reconstruction modes were established. The analysis to the reconstructive community indicates that the diversity of species in the community reduces with the increase of the eveness, and they are negative related (coefficient of correlation 0.94, linear regression Y = -0.14x + 0.75). Species diversity enlarges with the increase of the abundance, they are positive related (coefficient of correlation 0.85, linear regression Y = 0.17x -0.15). In all reconstruction modes, community T10 (Elymus sibiricus+ Bromus inermis+ Lolium multiflorum) has the best stability, and community T13 (Elymus nutans+ Lolium multiflorum+ Festuca rubral Agropyron desertorum) has the strongest rivalrousness. Among all tested species, three have the biggest community dominance, which are Elymus sibiricus, Elymus nutans, and Agropyron desertorum.In the artificial reconstructive communities, two original vegetations, which are Leymus secalinus and Carex praeclara, have the strongest encroachment ability. For the further study on the revegetation mode combined with original vegetations, the research on clonal growth properties was conduced during Leymus secalinus and Carex praeclara. The results show that the clonal architecture index of Leymus secalinus is 0.91 in accord with the guerilla, and the growth form index of Carex praeclara is 0.78 in accord with the phalanx. The clonal growth index of Leymus secalinus is 0.88, and that of Carex praeclara is 0.21. Leymus secalinus is suited to make use of resources distributed extensively, while Carex praeclara is fit for using resources distributed narrowly. Leymus secalinus and Carex praeclara have differentrisk-spreading modes. The risk-spreading of Leymus secalinus is on one or several lines, while that of Carex praeclara is on a plane.In order to reveal the dependence property and degree of Leymus secalinus and Carex praeclara on clonal integation effect when develop new habitats, they are tested by cutting the rhizomes. The results suggest that among all tested plant properties the extention growth highly depend on clonal integation effect, but which hardly affects the quantity and the shape. The adjustment of the vegetative growth and reproductive growth are controlled by clonal integation effect, Leymus secalinus requires more shoots when explanted, while Carex praeclara needs higher planting density.After analyzing the intrusive species of the artificial reconstructive communities, the experiments concerning the influence of abiotic ecological factors were performed. In the three factors, moisture, temperature and light, which effect the vegetation distribution, the low temperature and the strong UV-B radiation are quite important on the northwest plateau of Sichuan, so corresponding experiments were taken. Elymus sibiricus is the representative species in the northwest of Sichuan, and Lolium multiflorum, as the comparison, has the power to resist low temperature. During the research on gene expression difference between them, it is indicated that ATPase gene is involved in the metabolizability under low temperature adversity. The full length gene of Elymus sibiricus is obtained by 5'- RACE, the analysis to its expression under low temperature shows that during the 4 to 8 hours after low temperature disposal or the 16 to 24 hours when free from being intimidated, the transfer of atpA gene evidently enhances. The correlative analysis also indicates that the a -subunit of ATPase not only has the power to adjust the enzymatic activity, but also relates to the plant signal transduction under low temperature. During the process of separating the differential expression genes under low temperature, the discoveries of some genes and fragments connected with mRNA posttranscriptional ragulation, DNA repair, signal transduction and adversity enzymes (eg. methionine synthase ) lay a foundation for the further studies on the low temperture resistance of plateau plant.On the Tibetan plateau, the ozone hole is enlarging, and the UV-B radiation is strengthening. In this condition, the gene expression difference of Elymus sibiricusradiated by enhanced UV-B was analyzed, and some gene fragments homologous with phosphatidylserine decarboxylase gene and retrotransposons gene were seperated. It suggests that these fragments are involved in UV-B signal transduction and gene mutation. The rbcL gene controled by UV-B was seperated at the same time. The analysis on the full length gene of rbcL cloned by 5' RACE and its expression under enhanced UV-B shows that: Northern hybridization analysis on the rbcL expression during the time of enhanced UV-B radiation, showed that the mRNA level of the rbcL descended obviously after 6h enhancing UV-B radiation, and 60h later, the mRNA even couldn't be detected. The. E. sibiricus cv. 'chuancao No.2' growing in the plateau area for a long time, radiated strongly by the UV-B, the rbcL transcription of Elymus sibiricus L might be restrained like the plain plants which are sensitive to UV-B. This result provides a new clue for revealing the role of some factors such as PAR, temperature and the concentration of CO2 in the alpine plants adapting to strong UV-B radiation.