Light Potentials of Photosynthetic Energy Storage in the Field: What limits the ability to use or dissipate rapidly increased light energy?

Abstract

The responses of plant photosynthesis to rapid fluctuations in environmental conditions are thought to be critical for efficient capture of light energy. Such responses are not well represented under laboratory conditions, but have also been difficult to probe in complex field environments. We demonstrate an open science approach to this problem that combines multifaceted measurements of photosynthesis and environmental conditions, and an unsupervised statistical clustering approach. In a selected set of data on mint (Mentha sp.), we show that the "light potential" for increasing linear electron flow (LEF) and nonphotochemical quenching (NPQ) upon rapid light increases are strongly suppressed in leaves previously exposed to low ambient PAR or low leaf temperatures, factors that can act both independently and cooperatively. Further analyses allowed us to test specific mechanisms. With decreasing leaf temperature or PAR, limitations to photosynthesis during high light fluctuations shifted from rapidly-induced NPQ to photosynthetic control (PCON) of electron flow at the cytochrome b6f complex. At low temperatures, high light induced lumen acidification, but did not induce NPQ, leading to accumulation of reduced electron transfer intermediates, a situation likely to induce photodamage, and represents a potential target for improving the efficiency and robustness of photosynthesis. Finally, we discuss the implications of the approach for open science efforts to understand and improve crop productivity.