Peterson R B
Department of Biochemistry and Genetics, The Connecticut Agricultural Experiment Station, 123 Huntington St., New Haven, Connecticut 06504.
Plant Physiol. 1991 Dec;97(4):1388-94. doi: 10.1104/pp.97.4.1388.
The interactive effects of irradiance and O(2) and CO(2) levels on the quantum yields of photosystems I and II have been studied under steady-state conditions at 25 degrees C in leaf tissue of tobacco (Nicotiana tabacum). Assessment of radiant energy utilization in photosystem II was based on changes in chlorophyll fluorescence yield excited by a weak measuring beam of modulated red light. Independent estimates of photosystem I quantum yield were based on the light-dark in vivo absorbance change at 830 nanometers, the absorption band of P700(+). Normal (i.e. 20.5%, v/v) levels of O(2) generally enhanced photosystem II quantum yield relative to that measured under 1.6% O(2) as the irradiance approached saturation. Photorespiration is suspected to mediate such positive effects of O(2) through increases in the availability of CO(2) and recycling of orthophosphate. Conversely, at low intercellular CO(2) concentrations, 41.2% O(2) was associated with lower photosystem II quantum yield compared with that observed at 20.5% O(2). Inhibitory effects of 41.2% O(2) may occur in response to negative feedback on photosystem II arising from a build-up in the thylakoid proton gradient during electron transport to O(2). Covariation between quantum yields of photosystems I and II was not affected by concentrations of either O(2) or CO(2). The dependence of quantum yield of electron transport to CO(2) measured by gas exchange upon photosystem II quantum yield as determined by fluorescence was unaffected by CO(2) concentration.
在25摄氏度的稳态条件下，对烟草（Nicotiana tabacum）叶片组织中光系统I和光系统II的量子产率受光照强度、氧气和二氧化碳水平的交互作用进行了研究。基于调制红光弱测量光束激发的叶绿素荧光产率变化，评估了光系统II中辐射能的利用情况。光系统I量子产率的独立估计基于830纳米（P700(+)的吸收带）处的光暗体内吸光度变化。当光照强度接近饱和时，相对于在1.6%氧气条件下测得的光系统II量子产率，正常（即20.5%，v/v）水平的氧气通常会提高该量子产率。据推测，光呼吸通过增加二氧化碳的可用性和正磷酸盐的循环来介导氧气的这种积极作用。相反，在低细胞间二氧化碳浓度下，与在20.5%氧气条件下观察到的情况相比，41.2%氧气与较低的光系统II量子产率相关。41.2%氧气的抑制作用可能是由于在电子传递给氧气过程中类囊体质子梯度积累对光系统II产生负反馈所致。光系统I和光系统II量子产率之间的协变不受氧气或二氧化碳浓度的影响。通过气体交换测量的电子传递给二氧化碳的量子产率对光系统II量子产率（由荧光测定）的依赖性不受二氧化碳浓度的影响。
