Graduate School of Life Sciences, Tohoku University, Aoba, Sendai 980-8578, Japan.
Funct Plant Biol. 2021 Jul;48(8):815-826. doi: 10.1071/FP20365.
Solar-induced chlorophyll (chl) fluorescence (SIF) has been shown to be positively correlated with vegetation photosynthesis, suggesting that it is a useful signal for understanding of environmental responses and spatial heterogeneity of photosynthetic activity at various scales from leaf to the globe. Photosynthesis is often inhibited in stressful environments (photoinhibition), but how photoinhibition influences the relationship between photosynthesis and chl fluorescence remains unclear. Here, I studied light energy allocation among photosynthesis, chl fluorescence and heat dissipation in photoinhibited leaves and tested whether photosynthesis in photoinhibited leaves can be evaluated from chl fluorescence and reflectance spectra in remote sensing. Chl fluorescence and reflection spectra were examined with the pulse amplified modulation (PAM) system and spectroradiometer, respectively. Photoinhibited leaves had lower photosynthetic rates and quantum yields of photochemistry (ΦP) and higher chl fluorescence yields. Consequently, photosynthesis was negatively correlated with chl fluorescence, which contrasts the positive relationships between photosynthesis and SIF observed in past remote sensing studies. This suggests that vegetation photosynthesis evaluated solely from chl fluorescence may be overestimated if the vegetation is dominated by severely photoinhibited leaves. When a model of energy allocation was applied, ΦP estimated from chl fluorescence and photochemical reflectance index (PRI) significantly correlated with the observed ΦP, suggesting that the model is useful to evaluate photosynthetic activities of photoinhibited leaves by remote sensing.
太阳诱导叶绿素荧光（SIF）已被证明与植被光合作用呈正相关，这表明它是了解环境响应和光合作用在各种尺度上（从叶片到全球）的空间异质性的有用信号。在胁迫环境下，光合作用通常会受到抑制（光抑制），但光抑制如何影响光合作用与叶绿素荧光之间的关系尚不清楚。在这里，我研究了光抑制叶片中光合作用、叶绿素荧光和热耗散之间的光能分配，并测试了从叶绿素荧光和遥感反射光谱中是否可以评估光抑制叶片中的光合作用。使用脉冲放大调制（PAM）系统和分光辐射计分别检查了叶绿素荧光和反射光谱。光抑制叶片的光合速率和光化学量子产率（ΦP）较低，而叶绿素荧光产率较高。因此，光合作用与叶绿素荧光呈负相关，这与过去遥感研究中观察到的光合作用与 SIF 之间的正相关关系形成对比。这表明，如果植被主要由严重光抑制的叶片组成，则仅从叶绿素荧光评估植被光合作用可能会被高估。当应用能量分配模型时，从叶绿素荧光和光化学反射指数（PRI）估算的 ΦP 与观察到的 ΦP 显著相关，这表明该模型可用于通过遥感评估光抑制叶片的光合作用活性。
