The Physiological Response Of Saussurea Arenaria To The Stresses Of Temperature And UV-B

Saussurea is mainly distributed in highland areas, while the climate in the region ismainly in dry, cold and strong ultraviolet radiation and high solar radiation mainly.Underthe combined effects of these environmental factors, the morphology and growth ofSaussurea is greatly affected and restricted. In order to adapt the different environmentalstress, the physiological and biochemical aspects response of Saussurea species is aneffective way to enhance adapt ability. Saussurea arenaria Maxim belongs to theAsteraceae (Compsitae) perennial herb, grown mainly in Gansu Gannan TibetanAutonomous Prefecture. In this paper, it was studied the kinds of biochemical changes ofthe S.a management related parameters at different temperatures and ultraviolet radiationconditions. Research shows:1Effect of temperature on the S.acooperation is increasing with temperature, it was significantly higher in thetranspiration rate,intercellular CO2concentration, stomatal conductance and netphotosynthetic rate of S.a. The best temperature of photosynthesizing is about15℃. Whenthe temperature has reached30℃, the index is significantly inhibited.2Effect of temperature on the chlorophyll fluorescence characteristics of S.aThe real-time fluorescence Ft of Saussurea leaves increased significantly while thetemperature was rising. The real-time fluorescence Ft of Saussurea leaves reachedmaximum at the15℃and25℃, then it was the optimum growth temperature of S.a atGannan region. When the temperature was30℃, the real-time fluorescence wassignificantly lower than15℃and25℃. In addition, the high temperatures inhibited thekey enzyme activity of the xanthophyll cycle, affecting the xanthophyll cycle, so it leadedto the photosynthetic conversion efficiency of Saussurea blade increase with the increasingtemperature. It was maximum at25℃,but the photosynthetic conversion began to beinhibited at30℃. While the temperature stress led to reflect PSII electron transportcapacity related fluorescence parameters Fm and ETR decrease significantly, itindicated that the high temperature PSII electron transport was severely disrupted andinhibited by light. The ETR and Y (II) value in the hypothermia treatment groups is higher,less decline and in their ability to protect themselves better. When the temperature rosedramatically, the ETR and Y (II) value declined dramatically.It indicated that the lightwas serious injury. Temperature treatment had no significant effect on the S.a in thepotential maximum photosynthetic capacity.3Effect of temperature on related enzyme activities of S.aEffect of hypothermia on related enzyme activities of S.a mainly asfollows: SOD activity at low temperature, MDA Content and H2O2content didnotchange significantly. In the high-temperature treatment groups, SOD activity wasinhibited, H2O2levels were significantly increased, but MDA levels did not change significantly. When the temperature rose to a certain extent, it was weakened theantioxidant ability of S.a which grown in the alpine region.4Effects of UV-B on the S.a photosynthesisWhen the UV-B radiation reached the maximum, a part of photosynthesis index wasinhibited significantly. The UV-B radiation reduced significantly the net photosyntheticrate. When the radiation dose was10levels, the net photosynthetic rate of Saussurea bladesreduced significantly.15levels was the lowest value.5Effect of UV-B on chlorophyll fluorescence parametersIn the lower dose of UV-B under treatment, Fm’ in3class and five-levelradiation-treated group was significantly higher than the control group. But Y(II) in three-level and five-level radiation-treated group was significantly lower than thecontrol group. When UV-B radiation dose is high (10-level or15-level), Ft wassignificantly lower than the control group. Y (II) in the high-dose treatment group wassignificantly lower than the control group. When the radiation treatment was a lowdose, ETR reduced significantly. When the radiation treatment was a high dose,ETR increased significantly, but it had no significant difference with the control group.Compared with the control group, when the radiation dose did not exceed the middle, NPQwas increasing with the increasing radiation dose. When the UV-B radiation reached15levels, NPQ was maximum. When the radiation dose exceeds intermediate, NPQ reducedsignificantly with the increasing radiation dose. Therefore, the initial value ofqP, NPQ and Fm’ increased significantly compared with the control group. When theradiation dose added to a certain extent, they all decreased significantly.6Effect of UV-B on SOD, MDA and H2O2With a UV process, the increasing ultraviolet radiation had no significant effect to theMDA levels. But when it achieved15levels, the SOD content reduced significantly whilethe H2O2content was increasing. When the UV radiation added to a certain extent, theantioxidant capacity of Saussurea that grown in the alpine region was weaker.