Botanical Institute (Plant Physiology), University of Karlsruhe, Kaiserstrabe 12, D-7500, Karlsruhe, FRG.
Photosynth Res. 1987 Jan;14(3):229-40. doi: 10.1007/BF00032707.
Heat emitted during non-radiative de-excitation was determined in vivo by the photoacoustic method. The dependence of the photoacoustic signal on the length of the pulses (modulation frequency) of the excitation light and the effect of continuous light, which saturates photosynthesis but does not directly contribute to the signal, are described. The induction kinetic of heat emission measured with intact leaves differed only slightly from the induction kinetic of fluorescence (Kautsky effect) detected in parallel. The photoacoustic signal at high modulation frequencies (279 Hz), which represents the signal of heat emission, and the photoacoustic signal at low modulation frequencies (17 Hz), interpreted as a signal of pulsed oxygen evolution superimposed on the heat emission, were measured with leaves before and after photoinhibition. It was demonstrated that after photoinhibition the decrease in fluorescence yield and in photosynthetic activity (here detected as photoacoustic signal at 17 Hz) are paralleled by an increase in the yield of non-radiative deexcitation (photoacoustic signal at 279 Hz). The increase of heat emission, which has been hypothized for photoinhibited leaves, could now be proved by measuring the induction kinetics of the photoacoustic signal.
非辐射去激发过程中释放的热量通过光声法在体内进行测定。描述了光声信号与激发光脉冲长度（调制频率）的关系以及连续光的作用，连续光虽然会使光合作用饱和，但不会直接产生信号。用完整叶片测量的热释放感应动力学与同时检测到的荧光（卡尔斯基效应）感应动力学几乎没有差异。在高调制频率（279 Hz）下测量的光声信号（代表热释放信号）和在低调制频率（17 Hz）下测量的光声信号（解释为叠加在热释放上的脉冲氧演化信号）与光抑制之前和之后的叶片进行了测量。结果表明，光抑制后，荧光产率和光合作用活性（此处以 17 Hz 下的光声信号检测）下降，同时非辐射去激发的产率（279 Hz 下的光声信号）增加。已经假设光抑制叶片会增加热量释放，现在可以通过测量光声信号的感应动力学来证明这一点。
