Photosystem I (PSI) is a major player in the light reactions of photosynthesis. In higher plants, it consists of a core complex and four external antennae, Lhca1–4 forming the PSI–light-harvesting complex I (LHCI) supercomplex. The protein and pigment composition as well as the spectroscopic properties of this complex are considered to be identical in different higher plant species. In addition to the four Lhca, a pool of mobile LHCII increases the antenna size of PSI under most light conditions. In this work, we have first investigated purified PSI complexes and then PSI in vivo upon long-term dark-adaptation of four well-studied plant species: Arabidopsis thaliana, Zea mays, Nicotiana tabacum and Hordeum vulgare. By performing time-resolved fluorescence measurements, we show that LHCII is associated with PSI also in a dark-adapted state in all the plant species investigated. The number of LHCII subunits per PSI is plant-dependent, varying between one and three. Furthermore, we show that the spectroscopic properties of PSI–LHCI supercomplexes differ in different plants.

光系统 I (PSI) 是光合作用光反应的主要参与者。在高等植物中，它由一个核心复合体和四个外部触角 Lhca1-4 组成，形成 PSI-光捕获复合体 I (LHCI) 超复合体。这种复合物的蛋白质和色素组成以及光谱特性被认为在不同的高等植物物种中是相同的。除了四个 Lhca 之外，移动 LHCII 池在大多数光照条件下增加了 PSI 的天线尺寸。在这项工作中，我们首先研究了纯化的 PSI 复合物，然后研究了四种经过充分研究的植物物种的长期暗适应后体内的 PSI：拟南芥、玉米、烟草和大麦。. 通过执行时间分辨荧光测量，我们表明 LHCII 与 PSI 相关，在所有研究的植物物种中也处于暗适应状态。每个 PSI 的 LHCII 亚基数量取决于植物，在 1 到 3 之间变化。此外，我们表明 PSI-LHCI 超复合物的光谱特性在不同植物中有所不同。