Dynamic non‐photochemical quenching in plants: from molecular mechanism to productivity

Abstract

Summary Photoprotection refers to a set of well defined plant processes that help to prevent the deleterious effects of high and excess light on plant cells, especially within the chloroplast. Molecular components of chloroplast photoprotection are closely aligned with those of photosynthesis and together they influence productivity. Proof of principle now exists that major photoprotective processes such as non‐photochemical quenching (NPQ) directly determine whole canopy photosynthesis, biomass and yield via prevention of photoinhibition and a momentary downregulation of photosynthetic quantum yield. However, this phenomenon has neither been quantified nor well characterized across different environments. Here we address this problem by assessing the existing literature with a different approach to that taken previously, beginning with our understanding of the molecular mechanism of NPQ and its regulation within dynamic environments. We then move to the leaf and the plant level, building an understanding of the circumstances (when and where) NPQ limits photosynthesis and linking to our understanding of how this might take place on a molecular and metabolic level. We argue that such approaches are needed to fine tune the relevant features necessary for improving dynamic NPQ in important crop species.

Atomic structure of a mitochondrial complex I intermediate from vascular plants

“…Thus, CI* may provide additional energy-converting flexibility to plants’ electron flow and energy conservation. This would be analogous to the flexibility seen for the electron transport chain of chloroplasts, which employ several dynamic mechanisms at different levels of regulation to adjust the H + :e - coupling and the energetic and redox outputs to changing environmental conditions ( Heber and Kirk, 1975 ; Scheibe et al, 2005 ; Rochaix, 2011 ; Murchie and Ruban, 2020 ).…”

Arbuscular Mycorrhizal Symbiosis Enhances Photosynthesis in the Medicinal Herb Salvia fruticosa by Improving Photosystem II Photochemistry

“…Efficient photoprotective mechanisms are associated with avoidance of excess energy in chloroplasts [ 79 ] as it was observed in the inoculated plants, implying that inoculation contributes to prevention of excess excitation energy at PSII ( Figure 7 d). It is well defined that NPQ and photoinhibition are strongly interdependent [ 80 , 81 , 82 ] but how much NPQ or dissipation is needed to successfully limit photoinhibition is a complex question to answer [ 83 , 84 ].…”

Photoprotective energy dissipation is greater in the lower, not the upper, regions of a rice canopy: a 3D analysis

“…This is seen in the accumulation of xanthophyll cycle pigmentation at high and low growth light intensities. The explanations for this observation may be critical when discussing the trade offs between using light efficiently for photosynthesis and preventing photoinactivation and photooxidation (discussed at length in (Kromdijk et al, 2016;Hubbart et al, 2018;Murchie and Ruban, 2020;Wang et al, 2020). First the lower leaves should exploit brief periods of high light known as sunflecks (Figure 6c) which are more common in lower regions.…”

“…growing conditions), genetic adaption, and physiological status (Aro et al, 1993;Murchie and Niyogi, 2011;Demmig-Adams et al, 2012). The process employed by plants to relieve excitation pressure on the photosynthetic membrane is nonphotochemical quenching (NPQ) of chlorophyll fluorescence, in which excess energy is dissipated harmlessly as heat (Horton and Ruban, 1992;Jahns and Holzwarth, 2012;Ruban, 2016;Murchie and Ruban, 2020). The fastest component of NPQ is qE, or energy-dependent quenching, and is triggered by the generation of a pH gradient across the thylakoid membrane (Krause, 1974;Horton et al, 2005;Zulfugarov et al, 2007).…”