On the regulation of photosynthesis in pea leaves exposed to oscillating light

Plants grow in nature often in fluctuating irradiance. In the laboratory, the dynamics of photosynthesis is usually explored by instantaneously exposing dark-adapted plants to constant light and detecting the dark-to-light transient, which is only a poor approximation of natural phenomena. Aiming at a better approximation, we exposed pea leaves to oscillating light and measured, during oscillations, changes in function of photosystem I and II and of the proton-motive force at the thylakoid membrane. The dynamics depends on the oscillation period, leaving information about the regulatory networks. As demonstrated for selected period of the oscillation of 60 s, the regulations try to keep reactions centres of photosystems I and II open. A possible evaluation of obtained data is presented and involvement of particular processes in regulation of photosynthesis is discussed. The forced oscillations provide information-rich fingerprint of complex regulatory networks. Further progress in understanding the networks is expected from experiments involving chemical interventions, plant mutants, and by using mathematical modelling and the system identification and system control tools, as already applied in other parts of science. Highlight Measurement of photosynthetic signals during illumination of plants by light, whose intensity oscillates as sinus function provides information about regulation of photosynthesis in fluctuating light.