Institute of Plant Physiology, Biological Research Center, Hungarian Academy of Sciences, P.O. Box 521, H-6701, Szeged, Hungary.
Planta. 1989 Oct;179(3):349-58. doi: 10.1007/BF00391080.
Flash-induced primary charge separation, detected as electrochromic absorbance change, the operation of the cytochrome b/f complex and the redox state of the plastoquinone pool were measured in leaves, protoplasts and open-cell preparations of tobacco (Nicotiana tabacum L.), and in isolated intact chloroplasts of peas (Pisum sativum L.). Addition of 0.5-5 mM KCN to these samples resulted in a large increase in the slow electrochromic rise originating from the electrogenic activity of the cytochrome b/f complex. The enhancement was also demonstrated by monitoring the absorbance transients of cytochrome f and b 6 between 540 and 572 nm. In isolated, intact chloroplasts with an inhibited photosystem (PS) II, low concentrations of dithionite or ascorbate rendered turnover of only 60% of the PSI reaction centers, KCN being required to reactivate the remainder. "Silent" PSI reaction centers which could be reactivated by KCN were shown to occur in protoplasts both in the absence and presence of a PSII inhibitor. Contrasting spectroscopic data obtained for chloroplasts before and after isolation indicated the existence of a continuous supply of reducing equivalents from the cytosol.Our data indicate that: (i) A respiratory electron-transport pathway involving a cyanide-sensitive component is located in chloroplasts and competes with photosynthetic electron transport for reducing equivalents from the plastoquinone pool. This chlororespiratory pathway appears to be similar to that found in photosynthetic prokaryotes and green algae. (ii) There is an influx of reducing equivalents from the cytosol to the plastoquinone pool. These may be indicative of a complex respiratory control of photosynthetic electron transport in higher-plant cells.
光诱导的初级电荷分离，表现为电致变色吸收变化，细胞色素 b/f 复合物的作用以及质体醌库的氧化还原状态，在烟草（Nicotiana tabacum L.）的叶片、原生质体和开室制剂以及豌豆（Pisum sativum L.）的分离完整叶绿体中进行了测量。向这些样品中添加 0.5-5 mM KCN 会导致源自细胞色素 b/f 复合物的电致活动的缓慢电致变色上升大幅增加。通过监测细胞色素 f 和 b 6 在 540 和 572nm 之间的吸收瞬变也证明了增强作用。在具有抑制的 PS II 的分离完整的叶绿体中，低浓度的连二亚硫酸盐或抗坏血酸使 PSI 反应中心的 60%发生周转，需要 KCN 来重新激活其余部分。可以通过 KCN 重新激活的“沉默”PSI 反应中心在不存在和存在 PSII 抑制剂的情况下在原生质体中均被证明存在。对叶绿体分离前后获得的对比光谱数据表明，质体醌库从胞质溶胶中连续供应还原当量。我们的数据表明：（i）涉及氰化物敏感组分的呼吸电子传递途径存在于叶绿体中，并与光合电子传递竞争来自质体醌库的还原当量。这种叶绿体呼吸途径似乎类似于在光合原核生物和绿藻中发现的途径。（ii）有来自胞质溶胶的还原当量流入质体醌库。这些可能表明高等植物细胞中光合作用电子传递的复杂呼吸控制。
