Inverse Yield Changes of Heat and Fluorescence During Photoinhibition of Photosynthesis

1987

Photosynth Res

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.

Section: Discussionmentioning

confidence: 83%

Induction kinetics of heat emission before and after photoinhibition in cotyledons of Raphanus sativus

1987

Photosynth Res

“…The partial parallelism between heat production and <7E-quenching would confirm the assumption that the establishment of the proton gradient across the thylakoid m embrane results in heat illumination time/min [ 201 ] production. During a photoinhibitory treatment, the high-frequency pa signal rises parallel to the decrease of the fluorescence signal (Buschmann & Prehn 1988). This demonstrates that the absorbed light energy is increasingly transferred into heat.…”

Section: (A) Kinetics (I) Induction Kineticsmentioning

confidence: 86%

Photoacoustic measurements: application in plant science

Phil. Trans. R. Soc. Lond. B

1989

By means of the photoacoustic effect light-induced heat can be detected, which is produced during non-radiative de-excitation following absorption of light. This paper gives an overview of the current knowledge of photoacoustic measurements. First, the principle of detection and the different instrumentations are outlined in general. Then the applications of photoacoustic measurements in plant science and in particular in photosynthesis research are described in detail, ( a ) The induction kinetics of intact leaves at high modulation frequencies (where the signal is only determined by heat production) are contrasted with those at low modulation frequencies (where the signal can be determined by photosynthetic oxygen evolution superimposed on the heat production). Examples for ( b ) the determination of time constants and for ( c ) the measurement of the time delay between the excitation and the detection of the signal (phase) are given. Finally, ( d ) photoacoustic spectra are described. These can be used to determine the pigment composition, the depth profile, the efficiency of energy transfer and the pigment activity of a sample.

“…Quantum yield of non-radiative de-excitation determined by PA measurements has directly been compared to quantum yield of fluorescence (Vacek et al, 1979;Buschmann, 1987;Buschmann and KocsBnyi, 1989). The increased quantum yield of heat production during photoinhibition has been demonstrated by PA measurements (Buschmann and Prehn, 1988). Quantum yield of photosynthetic energy storage has been compared in isolated PS I1 particles, broken chloroplasts and bundle sheath cells ofZea mays (Popovic et al, 1988).…”

Section: Energy Transfer and Photosynthetic Quantum Yieldmentioning

confidence: 99%

Photoacoustic Spectroscopy and its Application in Plant Science

1990

Botanica Acta

Self Cite

The principles of photoacoustic spectroscopy are outlined. This new and still developing technique enables one to detect non-radiative de-excitation processes. It is possible to distinguish between signals emenating from different depths of the sample. In plant science photoacoustic spectroscopy has mainly been applied in photosynthesis research. Here it allows the detection of gross oxygen evolution and gives information about the energy balance of the primary photosynthetic reaction.