| By taking Nitraria tangutorum as the research object in this thesis, several physiological and biochemical indexes of Nitraria tangutorum from three geographic provenances (Wuwei,Zhangye and Jiuquan) under PEG-6000 stress and several physiological and biochemical indexes of Nitraria tangutorum in different habitats from east to west in Gansu province were measured. The main results were summarized as follows:(1) With water gradient decreasing from east to west in Gansu province, the contents of MDA in leaves of Nitraria tangutorum in different habitats increased, accompanied by increasing of the O- .2 production rate and the activities of SOD, POD and CAT and the content of osmoregulation substances such as free proline, soluble sugar and soluble protein, which could maintaine the lower water potential of Nitraria tangutorum to resist damage of drought stress.(2) Net photosynthetic rate of Nitraria tangutorum in different habitats from east to west appeared as single peak curves, among which Lanzhou was higher than Zhangye and Wuwei and was significantly higher than Jiuquan; diurnal variation of transpiration rate of Nitraria tangutorum in different habitats appeared as single peak curves. Among these habitats, Lanzhou was higher than Zhangye and Wuwei and was significantly higher than Jiuquan; diurnal variation of water use efficiency was similar to net photosynthetic rate. Net photosynthetic rate of Nitraria tangutorum was double regulated by stomata factor as well as non-stomata factor.(3) Reaction center of PSⅡof Nitraria tangutorum in different habitats from east to west was destroyed, among which Jiuquan was destroyed more seriously than Zhangye, Wuwei and Lanzhou; conversion efficiency of primary light energy (Fv/Fm) of PSⅡdecreased, but the time of conversion efficiency of primary light energy of PSⅡin Jiuquan was significantly advanced than that of other habitats; the quantum yield of PSⅡelectron transport (φPSⅡ) decreased. Among them, the descending in Jiuquan was lower than that of other habitats while the descending in Zhangye and Wuwei was lower than Lanzhou. Light energy which was absorbed in Jiuquan,Wuwei and Zhangye dissipated more in form of heat energy, but light energy in Lanzhou was used more often in form of photochemical reaction.(4) Under PEG osmotic stress:A: Relative water content of Wuwei provenance was higher than Zhangye and Jiuquan provenances. With the increasing of stress concentration and the prolongeding of stress time, relative water content of three provenances showed a trend of decreasing. Wuwei provenance reduced with the most extent and the decreasing range of Jiuquan provenance was the smallest. Relative water conten dropped to the lowest value under 72h stress and showed significant difference to contrast.B: With the increasing of stress concentration and the prolongeding of stress time, the MDA content of three provenances showed the trend of increasing. When the stress time is shorter, the MDA content had a significant increasing compared with the control, but when the stress time was longer, increasing range slowed down. The MDA conten had significant difference compared with contrast (P<0.05) and the accumulation of Wuwei provenance was the most obvious.C: The activity of Superoxide Dismutase (SOD) of three provenances showed the trend of increasing.After different stress, the ativity of Catalase(CAT) had great difference. Under low concentration of PEG osmotic stressed(5%), the CAT activity increased first and decreased afterwards. Under 10% and 15% concentration of PEG osmotic stressed,the CAT activity of three provenances dropped below the level of control. Under 20% concentration of PEG osmotic stressed,the CAT activity of three provenances increased first and decreased afterwards. The CAT activity of Jiuquan provenance had the greater accumulation than Zhangye and Wuwei provenance.D: With the increasing of stress concentration and the prolongeding of stress time, the Pro, SP content of three provenances showed the trend of increasing. The Pro content of Jiuquan provenance had the greater accumulation than Zhangye and Wuwei provenance. With the increasing of stress concentration and the prolongeding of stress time, the SS content of Zhangye provenance showed the trend of increasing, but the SS content of Wuwei and Jiuquan?increased first and decreased afterwards. They were all significantly higher than contrast.E: The chlorophyll content of Jiuquan provenance had the greater accumulation than Zhangye and Wuwei provenance. Chlorophyll a and chlorophyll b had the same trend as chlorophyll.(5) Correlation analysis showed that the relative water content showed a highly significant negative correlation with SOD, Pro, SP, SS, MDA and Chl. MDA was in a highly significant correlation with SOD, Pro, SP, and SS. Chl was in a highly significant correlation or significant correlation with SP, MDA, Pro and SS. There was highly significant correlation or significant correlation between Pro, SS, SP and SOD.(6) The principal component analysis showed that the first principal component of Nitraria tangutorum was RWC, Pro, SS, SP, MDA and Chl, the second principal component was SOD, and the third principal component was CAT.(7) The results of subordination function method of drought resistance for Nitraria tangutorum under osmotic stress showed their resistance ability was as follows: Jiuquan habitat>Zhangye habitat>Wuwei habitat.
|
PDF Full Text Request