Schansker Gert
Heinz Walz GmbH, Eichenring 6, 91090, Effeltrich, Germany.
Photosynth Res. 2022 Sep;153(3):191-204. doi: 10.1007/s11120-022-00934-7. Epub 2022 Jul 17.
Photosynthetic Control is defined as the control imposed on photosynthetic electron transport by the lumen-pH-sensitive re-oxidation of plastoquinol (PQH) by cytochrome bf. Photosynthetic Control leads at higher actinic light intensities to an electron transport chain with a (relatively) reduced photosystem (PS) II and PQ pool and a (relatively) oxidized PS I. Making Light Curves of more than 33 plant species with the recently introduced DUAL-KLAS-NIR (Chl a fluorescence + the redox states of plastocyanin (PC), P700, and ferredoxin (Fd)) the light intensity-dependent induction of Photosynthetic Control was probed and characterized. It was observed that PC became completely oxidized at light intensities ≤ 400 µmol photons m s (at lower light intensities in shade than in sun leaves). The relationship between qP and P700(red) was used to determine the extent of Photosynthetic Control. Instead of measuring the whole Light Curve, it was shown that a single moderate light intensity can be used to characterize the status of a leaf relative to that of other leaves. It was further found that in some shade-acclimated leaves Fd becomes again more oxidized at high light intensities indicating that electron transfer from the PQ pool to P700 cannot keep up with the outflow of electrons on the acceptor side of PS I. It was observed as well that for NPQ-induction a lower light intensity (less acidified lumen) was needed than for the induction of Photosynthetic Control. The measurements were also used to make a comparison between the parameters qP and qL, a comparison suggesting that qP was the more relevant parameter.
光合控制被定义为细胞色素bf对质体醌醇（PQH）进行的由类囊体腔pH敏感的再氧化作用所施加于光合电子传递的控制。在较高的光化光强度下，光合控制导致电子传递链中光系统（PS）II和PQ库相对还原，而PS I相对氧化。利用最近推出的DUAL-KLAS-NIR（叶绿素a荧光 + 质体蓝素（PC）、P700和铁氧还蛋白（Fd）的氧化还原状态）对33种以上植物进行光曲线测量，探究并表征了光合控制的光强依赖性诱导。观察到在光强≤400 μmol光子 m⁻² s⁻¹时（在阴生叶片中比阳生叶片在更低光强下）PC完全氧化。利用qP与P700(red)之间的关系来确定光合控制的程度。研究表明，无需测量整个光曲线，单个适度光强就可用于表征一片叶子相对于其他叶子的状态。还进一步发现，在一些适应阴生环境的叶片中，在高光强下Fd再次变得更氧化，这表明从PQ库到P700的电子传递跟不上PS I受体侧电子的流出。还观察到，与光合控制的诱导相比，NPQ诱导所需的光强更低（类囊体腔酸化程度更低）。这些测量还用于比较qP和qL参数，比较结果表明qP是更相关的参数。
