荫蔽花生转入自然光照下光合作用的光抑制及光保护机制

Photo-inhibition and photo-protective mechanisms of shaded peanut leaves after re-exposure to natural light

为探明荫蔽花生转入自然光照下的光抑制及光合恢复过程中的光保护机制,为麦套花生高产栽培提供理论依据。大田条件下以花生品种白沙1016为材料,用遮阴网设置不遮光(Control)、遮光50%(S50)和遮光85%(S85)3个处理,研究荫蔽花生转入自然光照下光合荧光参数、活性氧离子产生速率及活性氧清除酶活性的变化动态。结果表明,遮阴解除后0~5d花生功能叶片净光合速率(Pn)和光系统Ⅱ最大光化学效率(F_v/F_m值)持续降低,Pn和F_v/F_m值各处理均表现为Control>遮光50%(S50)>遮光85%(S85);遮光50%和遮光85%处理净光合速率分别于遮阴解除后10d和20d逐渐恢复到对照水平,F_v/F_m值分别于遮阴解除后12和15d左右恢复对照水平。遮阴解除后0~10d反映热耗散强度的初始荧光F0值、非光化学淬灭系数(NPQ)显著上升,随后逐步降低恢复到对照水平。进一步研究表明,遮阴解除后0~5d超氧阴离子O_2^(-·)的产生速率迅速增加,第5d超氧阴离子O_2^(-·)产生速率S85>S50>Control;而后随SOD、CAT等活性氧清除酶活性的增强,超氧阴离子O_2^(-·)的产生速率降低。由以上可看出,遮阴解除后5d光合作用的光抑制或光破坏持续加重,活性氧的产生是导致光破坏的重要原因,热耗散和活性氧的清除在光合恢复中起重要的保护作用。

The objective of this study was to discover the mechanisms of the photo - inhibition and photo - pro-tection of peanut from shadow to high light, and further to provide a theoretical basis for high - yield cultivation of peanut intercropped with wheat. In our study, three treatments were set up from seedling emergency with u Baisha 1016”,and these treatments were（1 ） Control, with natural light; （2） S50, sunlight - shaded of 5 0 % by shade net; （3 ） S85, sunlight - shaded of 85 % . The photosynthetic and chlorophyll fluorescence parameter, superoxide production rate and activity of antioxidant enzymes were measured. Results showed that ： compared to those of the control with full light, the photosynthesis rate （Pn） and chlorophyll fluorescence parameter （ Fv /Fm ） of shading peanut leaves decrease continuously in the first 5d , the P n and FY /Fm of peanut ranked as Control 〉 S50 〉 S85 on the 5th day after shade removed. Pn under S50 and S85 treatments restored to the level of control on the 10th and 20th days after shade removed, and FY /Fm under S50 and S85 treatments restored to the level of Control on the 12th and 15th days after shade removed. Sunlight - shaded treatments significantly increased non - photochemical quenching （NPQ ） and initial fluorescence （_ F〇） within the first 0 - 10 days,and those were gradually reduced to the level similar to the countrol after 10 days. The active oxygen anion increased rapidly and ranked as S85 〉 S50 〉 Control on the 5th days after shade removed, yet the higher production of active oxygen anion was reduced with the increasing activities of superoxide dismutase （ SOD ） or catalase （CAT）. The thermal dissipation and antioxidant were important in improving the adaptability of peanut leaves to sudden intensive sunlight.