Light energy causes damage to Photosystem I (PSI) and Photosystem II (PSII). The majority of the previous photoinhibition studies have been conducted with PSII, which shows much larger photoinhibition than PSI; therefore, relatively little is known about the mechanism of PSI photoinhibition so far. A previous report showed that the photoinhibition action spectrum measured with PSI activity of isolated thylakoid is similar to the absorption spectrum of chlorophyll. However, it is known that the extent of PSI photoinhibition is much smaller in vivo compared to in vitro. It is also possible that the different extent of PSII photoinhibition, caused by different spectral light qualities, can affect the photoinhibition of PSI in vivo because PSI receives electrons from PSII. In the present research, to study the effect of light quality and the effect of the extent of PSII photoinhibition on the PSI photoinhibition in vivo, intact leaves were photoinhibited under four different light qualities. The rate coefficient of PSI photoinhibition was significantly higher in blue and red light compared to white light. The rate of PSI photoinhibition at the same photon-exposure was the largest in blue and red light and followed by white and green light. These results support the notion that light absorption by chlorophyll is responsible for the PSI photoinhibition, even in intact leaves. The variation among light colors in the relationships between the extent of photoinhibition of PSII and that of PSI indicate that PSI and PSII are independently photoinhibited with different mechanisms in the early stage of in vivo photoinhibition.

光能会对光系统 I (PSI) 和光系统 II (PSII) 造成损害。以前的大多数光抑制研究都是用 PSII 进行的，PSII 显示出比 PSI 大得多的光抑制；因此，到目前为止，对 PSI 光抑制的机制知之甚少。先前的报告表明，用分离的类囊体的 PSI 活性测量的光抑制作用光谱与叶绿素的吸收光谱相似。然而，众所周知，与体外相比，体内 PSI 光抑制的程度要小得多。也有可能是由不同光谱光质量引起的不同程度的 PSII 光抑制会影响 PSI 在体内的光抑制，因为 PSI 接收来自 PSII 的电子。在目前的研究中，为了研究光质的影响以及PSII光抑制程度对体内PSI光抑制的影响，在四种不同光质下对完整叶片进行光抑制。与白光相比，蓝光和红光下 PSI 光抑制的速率系数显着更高。在相同光子曝光下，PSI 光抑制率在蓝光和红光中最大，其次是白光和绿光。这些结果支持叶绿素的光吸收导致 PSI 光抑制的观点，即使在完整的叶子中也是如此。PSII光抑制程度与PSI光抑制程度之间关系的光色变化表明，在体内光抑制的早期阶段，PSI和PSII以不同的机制独立进行光抑制。