Institute of Bio- and Geosciences/Plant Sciences (IBG-2), Forschungszentrum Jülich, Wilhelm-Johnen-Straße, D-52428 Jülich, Germany.
Department of Biophysics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, Šlechtitelů 27, 783 71 Olomouc, Czech Republic.
Plant Physiol. 2021 Oct 5;187(2):646-661. doi: 10.1093/plphys/kiab317.
Foundations of photosynthesis research have been established mainly by studying the response of plants to changing light, typically to sudden exposure to a constant light intensity after dark acclimation or light flashes. This approach remains valid and powerful, but can be limited by requiring dark acclimation before time-domain measurements and often assumes that rate constants determining the photosynthetic response do not change between dark and light acclimation. We show that these limits can be overcome by measuring plant responses to sinusoidally modulated light of varying frequency. By its nature, such frequency-domain characterization is performed in light-acclimated plants with no need for prior dark acclimation. Amplitudes, phase shifts, and upper harmonic modulation extracted from the data for a wide range of frequencies can target different kinetic domains and regulatory feedbacks. The occurrence of upper harmonic modulation reflects nonlinear phenomena, including photosynthetic regulation. To support these claims, we measured chlorophyll fluorescence emission of the green alga Chlorella sorokiniana in light that was sinusoidally modulated in the frequency range 1000-0.001 Hz. Based on these experimental data and numerical as well as analytical mathematical models, we propose that frequency-domain measurements can become a versatile tool in plant sensing.
光合作用研究的基础主要是通过研究植物对光照变化的反应来建立的，通常是在暗适应或光闪烁后突然暴露于恒定光强下。这种方法仍然有效且强大，但可能会受到限制，需要在时域测量之前进行暗适应，并且通常假设决定光合作用响应的速率常数在暗适应和光适应之间不会改变。我们表明，通过测量植物对变化频率的正弦调制光的响应，可以克服这些限制。由于其性质，这种频域特征是在光适应的植物中进行的，无需事先进行暗适应。从广泛频率范围内的数据中提取的幅度、相移和上谐调制可以针对不同的动力学域和调节反馈。上谐调制的出现反映了非线性现象，包括光合作用调节。为了支持这些说法，我们测量了绿藻 Chlorella sorokiniana 在频率范围为 1000-0.001 Hz 的正弦调制光下的叶绿素荧光发射。基于这些实验数据以及数值和分析数学模型，我们提出频域测量可以成为植物感应的一种通用工具。
