PAM fluorescence of leaves of cherry laurel (Prunus laurocerasus L.) was measured simultaneously in the spectral range below 700 nm (sw) and above 700 nm (lw). A high-sensitivity photodiode was employed to measure the low intensities of sw fluorescence. Photosystem II (PSII) performance was analyzed by the saturation pulse method during a light response curve with subsequent dark phase. The sw fluorescence was more variable, resulting in higher PSII photochemical yields compared to lw fluorescence. The variations between sw and lw data were explained by different levels of photosystem I (PSI) fluorescence: the contribution of PSI fluorescence to minimum fluorescence (F₀) was calculated to be 14% at sw wavelengths and 45% at lw wavelengths. With the results obtained, the validity of an earlier method for the quantification of PSI fluorescence (Genty et al. in Photosynth Res 26:133–139, 1990, https://doi.org/10.1007/BF00047085) was reconsidered. After subtracting PSI fluorescence from all fluorescence levels, the maximum PSII photochemical yield (F_V/F_M) in the sw range was 0.862 and it was 0.883 in the lw range. The lower F_V/F_M at sw wavelengths was suggested to arise from inactive PSII reaction centers in the outermost leaf layers. Polyphasic fluorescence transients (OJIP or OI₁I₂P kinetics) were recorded simultaneously at sw and lw wavelengths: the slowest phase of the kinetics (IP or I₂P) corresponded to 11% and 13% of total variable sw and lw fluorescence, respectively. The idea that this difference is due to variable PSI fluorescence is critically discussed. Potential future applications of simultaneously recording fluorescence in two spectral windows include studies of PSI non-photochemical quenching and state I–state II transitions, as well as measuring the fluorescence from pH-sensitive dyes simultaneously with chlorophyll fluorescence.

在低于 700 nm (sw) 和高于 700 nm (lw) 的光谱范围内同时测量樱桃月桂 ( Prunus laurocerasus L.)叶子的 PAM 荧光。使用高灵敏度光电二极管来测量 sw 荧光的低强度。在光响应曲线和随后的暗阶段期间，通过饱和脉冲方法分析光系统 II (PSII) 性能。与 lw 荧光相比，sw 荧光更易变，导致更高的 PSII 光化学产率。sw 和 lw 数据之间的差异可以通过不同水平的光系统 I (PSI) 荧光来解释：PSI 荧光对最小荧光的贡献 ( F ₀) 在 sw 波长下计算为 14%，在 lw 波长下为 45%。根据获得的结果，重新考虑了早期量化 PSI 荧光的方法（Genty 等人在 Photosynth Res 26:133–139, 1990，https://doi.org/10.1007/BF00047085）的有效性。从所有荧光水平减去 PSI 荧光后，最大 PSII 光化学产率 ( F _V / F _M ) 在 sw 范围内为 0.862，在 lw 范围内为 0.883。sw 波长下较低的F _V / F _M被认为是由最外层叶层中不活跃的 PSII 反应中心引起的。多相荧光瞬变（OJIP 或 OI ₁ I ₂P 动力学）在 sw 和 lw 波长同时记录：动力学的最慢阶段（IP 或 I ₂ P）分别对应于总变量 sw 和 lw 荧光的 11% 和 13%。这种差异是由可变的 PSI 荧光引起的想法受到了批判性的讨论。在两个光谱窗口中同时记录荧光的潜在未来应用包括研究 PSI 非光化学淬灭和状态 I-状态 II 跃迁，以及同时测量 pH 敏感染料的荧光和叶绿素荧光。