Zhang Chao, Pfündel Erhard E, Atherton Jon, Aalto Juho, Bai Jia, Pohja Toivo, Rajewicz Paulina A, Porcar-Castell Albert
Optics of Photosynthesis Laboratory, Institute for Atmospheric and Earth System Research (INAR)/Forest Sciences, Viikki Plant Science Centre (ViPS), University of Helsinki, Helsinki, 00014, Finland.
Heinz Walz GmbH, Eichenring 6, D-91090, Effeltrich, Germany.
Photosynth Res. 2025 Sep 4;163(5):45. doi: 10.1007/s11120-025-01166-1.
Pulse-amplitude modulated (PAM) chlorophyll fluorescence (ChlF) measurements provide a non-invasive method to study the regulation of the light reactions of photosynthesis in situ. PAM ChlF contributes also to the advancement of the interpretation of long-term observations of remotely sensed solar induced fluorescence by revealing the mechanistic connection between ChlF and photosynthetic function. However, long-term field PAM ChlF measurements remain uncommon due to challenges associated with the outdoor environment, instrument installation and maintenance, or data processing and interpretation. We here provide guidelines and recommendations to support long-term field installation of PAM ChlF systems, including the design of specialized field installation supports. We also introduce a dedicated R-package (LongTermPAM) to help users filter and analyse long-term data. Methods are demonstrated using two long-term datasets obtained with a MONI-PAM system (Monitoring PAM, Walz GmbH, Germany) on Scots pine and Norway spruce in a boreal forest. The LongTermPAM R-package helped filter spurious observations caused by dew, ice or snow, permitting calculation of photochemical (PQ) and non-photochemical quenching (NPQ) parameters and their associated yields. Finally, we illustrate how PQ and NPQ regulate the relationship between ChlF and photochemical yields, and discuss how variations in leaf PAR absorption, energy partitioning between photosystems II and I, and the contribution of photosystem I to the total ChlF signal can influence the interpretation of PAM ChlF, emphasizing the value of complementary measurements to capture variability in these factors. Although based on our experience with the MONI-PAM system in a boreal environment, most issues hereby addressed can be broadly applied to other long-term PAM monitoring systems and environments.
脉冲幅度调制（PAM）叶绿素荧光（ChlF）测量提供了一种非侵入性方法，用于原位研究光合作用光反应的调节。PAM ChlF还通过揭示ChlF与光合功能之间的机制联系，推动了对遥感太阳诱导荧光长期观测结果的解读。然而，由于与室外环境、仪器安装与维护或数据处理与解读相关的挑战，长期野外PAM ChlF测量仍然并不常见。我们在此提供指导方针和建议，以支持PAM ChlF系统的长期野外安装，包括专门野外安装支架的设计。我们还引入了一个专用的R包（LongTermPAM），以帮助用户筛选和分析长期数据。使用在北方森林中对苏格兰松和挪威云杉使用MONI-PAM系统（监测PAM，德国瓦尔兹有限公司）获得的两个长期数据集对方法进行了演示。LongTermPAM R包有助于筛选由露水、冰或雪引起的虚假观测值，从而能够计算光化学（PQ）和非光化学猝灭（NPQ）参数及其相关产量。最后，我们说明了PQ和NPQ如何调节ChlF与光化学产量之间的关系，并讨论了叶片对光合有效辐射（PAR）的吸收变化、光系统II和I之间的能量分配以及光系统I对总ChlF信号的贡献如何影响PAM ChlF的解读，强调了进行补充测量以捕捉这些因素变化的价值。尽管基于我们在北方环境中使用MONI-PAM系统的经验，但在此解决的大多数问题可广泛应用于其他长期PAM监测系统和环境。
