We rarely think of plants as being dynamic: often, they are simply part of the landscape or ornamentation near south-facing windows. In reality, they are in near-constant adaptation to their ever-changing surroundings. Take light, for example; natural environments have highly variable irradiance. Passing clouds, other plants, or human actions can all influence the amount of available light. Therefore, plants require adaptable systems that promptly regulate factors such as photosynthesis and photoprotection, which are relevant for their fitness and evolution.
However, there is some disconnect between natural settings and how laboratories generally study the dynamics of photosynthesis. Dark-adapted plants are often instantaneously exposed to constant light and examined during the dark-to-light transition. One way of overcoming this poor approximation is by mimicking natural conditions using fluctuating light—thus enriching our “understanding of the dynamics of photosynthetic regulation in nature”.
Forced response to oscillating light
A study published in the Journal of Experimental Botany proposes a better experimental approximation to gain new insights into the regulation of photosynthesis in pea plants (Pisum sativum). Researchers at Palacký University in the Czech Republic and Forschungszentrum Jülich in Germany exposed pea leaves to oscillating light, which “provided an information-rich fingerprint of complex regulatory networks.”
The oscillating sinusoidal red light used by the team can cover the whole range of distinct dynamic components as they occur in particular natural environments. It induced responses from the exposed plants in the form of photosynthetic signals containing additional waves or bumps named “forced oscillations.” These signals were then measured, analysed, and compared across different periods to infer the mechanisms regulating photosynthesis in fluctuating light.
More specifically, the researchers measured the chlorophyll fluorescent signal—a common way of sensing a plant’s response to light changes—among other reporters for photosynthesis. These reporters allowed for interrogations into how oscillating light changes the functioning and regulation of the main proteins and driving force of photosynthesis: photosystem I, photosystem II, and the proton motive force.
The team discovered that the dynamics of photosynthesis “depended on the oscillation period, revealing information about the underlying regulatory networks.” Notably, for a 60-second oscillation period, the photosynthetic regulation acted towards a stable functioning of the proteins even with a fluctuating input.
Another way of looking into photosynthesis
According to the authors, their work shows a high potential for forced oscillations in studying the function and regulation of photosynthesis. They expect to gain further insights by conducting new experiments involving “chemical interventions and plant mutants, and by using mathematical modelling and systems identification and control tools.”
This study was partly funded by the Horizon Europe EIC Pathfinder Open 2021 project DREAM. The methodologies and results being developed and analysed by the authors could prove essential on the journey to achieve the project’s aims: to exploit the dynamical regulation of photosynthesis to foster precision agriculture in optimized and controlled environments.