| Temperature is one of the basic conditions of survival and life to plants. Because of high altitude of Qinghai-Tibetan Plateau, the harsh environment there makes the plants subject to different degrees of chilling injury. Study on the cold resistance of plants not only has important significance in theoretical basis, but also extensive application value in solving the practical problems. Saussurea, being a common species, which is distributing in the Qinghai-Tibetan Plateau will inevitably under the influence of chilling injury. In this study, an experiment using ultraviolet spectrophotometry was conducted to investigate the effects of low temperature on physiological characteristics in three Saussurea species(S. Hieracioides, S. arenaria.and S. parviflora) distributing in Eastern Qinghai-Tibetan Plateau. The physiological indexes include MDA content, chlorophy content, proline content, relative electrical conductivity, soluble protein content, soluble sugar content, and antionxidant enzyme activity, which can be superoxide dismutase(SOD), peroxidase(POD) and catlase(CAT) acticity. The discussion will be carried out from the experimental data which can be concluded from the statistical analysis that how three Saussurea species respond under the low temperature stress, using the information provided by the physical signs, and to have a comparison among inter-species. This study is supposed to provide the theoretical foundation for protection of alpine meadow the eastern of Qinghai-Tibetan Plateau.The physiological characteristic of three Saussurea species under low temperature were measured in five stages(10℃, 5℃, 0℃,-5℃,-10℃). The results showed that:(1) The content of Chlorophyll a and Chlorophyll b in three Saussurea were decreased in order to reduce the active oxygen damage caused by excess light energy.The content of Chlorophyll a and Chlorophyll b of S. hieracioides is always the highest among them, which maybe a result that it benefits photosynthesis to produce more soluble sugar and soluble protein that can resist the damage from low temperature stress. This phenomenon can aslo be proved that the content of solublesugar and soluble protein of S. hieracioides is the highest among this three Saussurea species.(2) With the decrease of the temperature, three Saussurea species were damaged in a certain extent. The content of MDA and relative electrical conductivity were increased in varying degrees. And the rising tendency of S. hieracioides is the slowest one among them with the decreasing of temperature of low temperature stress.(3) To counter with the damage caused by low temperature, After treatment,Three kind of Saussurea activity of POD, SOD with CAT were strengthened. Howerer,with the decrease of stress temperature, the ability of antionxidant enzyme to resist chilling injury is limited. The antionxidant enzyme activity of S. arenaria and S.parviflora increased during the stress period.(4) Carotenoid, Pro, soluble sugar and soluble protein can reflect a certain degree of protection ability of cells when plant under the external environment stress. So the content of them in three Saussurea species increased to counter the damage caused by low temperature stress. However the abilities of plant resistance to low temperature stress are different. The content of soluble sugar and soluble protein of S. hieracioides showing a low growth or slow downward trend, there is a dramatic decline in the content of that four substances of S. parviflora.The above experimental results showed that the ability to resistance low temperature damage of S. hieracioides and S. arenaria is stronger than S. parviflora.This may be because S. hieracioides have stronger resistance to low temperature stress during long process of evolution. And the distribute elevation range of S.parviflora is minimum among these three Saussurea species. So the environment temperature is lower than S. hieracioides and S. arenaria. The ability to resist low temperature stress of S. parviflora is the worst. |
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