To know more about the site of O2 production in thylakoids, the Fv/Fm ratio was measured in parallel with the oxygen free-radical production detected by electron spin resonance (ESR) using Tiron as a probe in the isolated thylakoids of Scots pine (Pinus sylvestris L.). As the light intensity was strong enough to induce photoinhibition leading to reduction in the Fv/Fm ratio, the intensity of the TH·signal representing the superoxide production was enhanced. The TH·signal was also stimulated by 3-(3,4-dichloropheneyl)-1,1-dimethylurea but was suppressed by exogenous scavengers or by 2,6-dichlorophenol indophenol.Therefore, the superoxide production is closely related to photoinhibition in PSⅡ. The novel results may further promote research on the mechanism of photoinhibition and on the structure and function of PSⅡ as well.
光系统II的光抑制和超氧的产生
靳月华 陶大立*
（中国科学院沈阳应用生态研究所，沈阳110015）
摘要：为了更多地了解超氧在叶绿体中产生的部位 ,在测定欧洲赤松 (Pinussylvestris L .)针叶离体叶绿体的Fv/Fm比值的同时 ,以Tiron为探针 ,用电子自旋共振 (ESR)技术平行检测其氧自由基的产生。当光强达到足以引起光抑制并使Fv/Fm 比值下降时 ,指示超氧产生的TH·半醌自由基的信号强度也随之增加。这一信号的强度也可被二氯苯基二甲基脲 (DCMU)所增强 ,但被外源的自由基清除剂或二氯酚靛酚 (DCIP)所抑制。这表明超氧的产生和PSⅡ的光抑制密切相关。这些新的结果将可能促进对光合光抑制的机制和PSⅡ结构和功能的研究。
关键词： 光抑制；超氧；Fv/Fm；欧洲赤松；PSII；电子自旋共振
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