| This test was conducted in the network room of Food Crops Institute in Jiangsu Provincial Academy of Agricultural Sciences in2010. The tested material Liangyoupeijiu was provided by the Jiangsu Provincial Academy of Agricultural Sciences. The study was conducted to determine the effect of low intensity UV-B (1.6kJ·m-2·day-1) radiation stress on the photosynthetic and fluorescent parameters in the functional leaves of Liangyoupeijiu. It includes:(1) measuring chlorophyll fluorescence induction dynamics OJIP curve and related parameters with a portable fluorescence analyzer Handy PEA to analyze primary light energy conversion, energy distribution of reaction center and electron transport of acceptor side under low-intensity UV-B radiation stress;(2) determinating photosynthetic parameters of net photosynthetic rate,stomatal conductance and intercellular CO2concentration by CIRAS-2portable photosynthesis system to analyze the reason an Changes in capacity of the functional leaves photosynthesis during reproductive stage under low-intensity UV-B radiation stress;(3)determinating of the parameters of antioxidant system in the functional leavies through physiological and biochemical analysis techniques to annlyze the activities of antioxidant enzymes and changes of the antioxidants content under low-intensity UV-B radiation stress. The results showed that:(1) It made the chlorophyll content of Liangyoupeijiu functional leaves increased significantly under low-intensity UV-B radiation stress,In particular, the content of antenna pigment was higher than the amount of the reaction center pigment. Therefore, it increased the light acceptance area of the leaves of PSII, and promoted theoriginal light energy absorption and transmission. In the reaction center of PSII, the energy absorbed per unit reactor area of ABS/CS increased,and the energy into the electron transport chain ETo/CS increased correspondingly. The number of active reaction center RC/CS increased. The primary light energy conversion efficiency of PSII Fv/Fm improved.Thermal dissipation of energy did not change significantly. The results of fluorescence induction kinetics showed that the energy absorbed into the electron transport chain made the quantum of QA downstream electron transport cpEo increased. The degree of poenness of the active reaction center ψo increased. Therefore, the performance of PSII improved under low-intensity UV-B radiation.(2) From the full extension of the flag leaf to grain filling stage, net photosynthetic rate Pn, transpiration rate E and stomatal conductance Gs were at higher level. Stomatal limitation value Ls and net photosynthetic rate showed a significant positive correlation, Which showed that the net photosynthetic rate of change was caused by non-stomatal factors. To the latter part of aging, the low-intensity UV-B radiation made the net photosynthetic rate, transpiration rate and stomatal conductance increased.The intercellular CO2concentration Ci reduced. Therefore, low-intensity UV-B radiation improved leaf gas exchange parameters, especially in the late reproductive growth, which to some extent delayed leaf senescence.(3) The activity of SOD and POD increased under low-intensity UV-B radiation stresss. Especially to the late, the activity was higher than that in the control group, therefore improved the antioxidant capacity of the leaves. The content of superoxide anion and MDA by the treated group were lower than the control group, and the rate of rise was lower than the control group with the leaves senescence. Therefore, the activity of the leaves photosynthetic apparatus improved. The content of the leaves, antioxidants ASA and GSH increased. Therefore it improved the ability of active oxygen scavenging of the leaves and reduced the membrane lipid peroxidation of the leaves. Especially in the late, the content increased significantly comparing with the control group, thus it delayed the leaves senescence. The content of soluble sugar by the treated group decreased, resistance increased, therefore improving the resistance. |
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