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 critical for efficient conversion of light energy. These responses are not well-seen laboratory conditions and are difficult to probe in 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 ‘light potentials’ for linear electron flow and non-photochemical quenching (NPQ) upon rapid light increases are strongly suppressed in leaves previously exposed to low ambient photosynthetically active radiation (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 of electron flow at the cytochrome b 6 f complex. At low temperatures, high light induced lumen acidification, but did not induce NPQ, leading to accumulation of reduced electron transfer intermediates, probably inducing photodamage, revealing a potential target for improving the efficiency and robustness of photosynthesis. We discuss the implications of the approach for open science efforts to understand and improve crop productivity.

Photosynthetic mechanisms underlying NaCl-induced salinity tolerance in rice (Oryza sativa)

“…Light potential (LP), which is defined as the capacity of linear electron flow to respond to sudden changes in light intensity [ 24 ]. Hand-held MultispeQ 2.0 instruments ( https://photosynq.com ) were used to take measurements at DAP 7.…”

“…Water-soaked seedlings were moved to an artificial greenhouse for 1 h of acclimation (~ 50 mol m -2 s -1 ). The dynamic response of PSII quantum efficiency (Φ II ) and linear electron flow (LEF) was evaluated by the LP protocol (ambient, high PAR and then dark) after small modification [ 24 ]. The full protocol ( https://photosynq.org/projects/rapid-ps-responses- acclimation dmk-zuo) required more than 60 s, and most researchers could not steadily clamp a leaf in the instrument.…”

“…In the field condition, the majority of leaves are exposed to rapidly changing light throughout the day. The ability to use rapidly increased light energy during light fluctuations determined light conversion efficiency and crop biomass [ 24 ]. Such robustness measurement for photosynthesis has gained attention, however, these measurements are usually taken under strictly controlled condition.…”