NPQ_(T): a chlorophyll fluorescence parameter for rapid estimation and imaging of non‐photochemical quenching of excitons in photosystem‐II‐associated antenna complexes

Abstract

In photosynthesis, light energy is absorbed by light-harvesting complexes and used to drive photochemistry. However, a fraction of absorbed light is lost to non-photochemical quenching (NPQ) that reflects several important photosynthetic processes to dissipate excess energy. Currently, estimates of NPQ and its individual components (q , q , q and q ) are measured from pulse-amplitude-modulation (PAM) measurements of chlorophyll fluorescence yield and require measurements of the maximal yield of fluorescence in fully dark-adapted material (F ), when NPQ is assumed to be negligible. Unfortunately, this approach requires extensive dark acclimation, often precluding widespread or high-throughput use, particularly under field conditions or in imaging applications, while introducing artefacts when F is measured in the presence of residual photodamaged centres. To address these limitations, we derived and characterized a new set of parameters, NPQ , and its components that can be (1) measured in a few seconds, allowing for high-throughput and field applications; (2) does not require full relaxation of quenching processes and thus can be applied to photoinhibited materials; (3) can distinguish between NPQ and chloroplast movements; and (4) can be used to image NPQ in plants with large leaf movements. We discuss the applications benefits and caveats of both approaches.

Why Are There so Many Plant Species That Transiently Flush Young Leaves Red in the Tropics?

“…Plants can dissipate excessive light energy absorbed by lightharvesting complexes through non-photochemical quenching (NPQ), which is based on the xanthophyll cycle (Müller-Moulé et al, 2002;Tietz et al, 2017). NPQ as measured in this study does not represent the total capacity for non-photochemical quenching of the samples, but it is rather a measure of the instantaneous level of this process depending on the light incident on the sample surface, light absorptivity, energy pressure on the photosystems and photo-protective potential (i.e., xanthophyll pool size).…”

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

“…The new pNPQ technique (Ruban and Murchie, ), reviewed in Ruban () offered a way of measuring NPQ without the need for dark adaptation. It showed a feasibility for being utilized in studies where dynamics are of greater interest and comparisons of absolute values between species for example are of less interest (Tietz et al , ). All of this needs to take into consideration that not all NPQ will act in a protective manner and it is necessary to consider measurements that distinguish non‐protective NPQ (Ruban and Belgio, ; Ware et al , ,b).…”

Photoprotective, excited-state quenching mechanisms in diverse photosynthetic organisms

“…How and where the different protein complexes involved in NPQ interact remain an open question. The availability of increasingly advanced techniques in spectroscopy, molecular biology and biochemistry, and computational modelling are very important tools in tackling these unknowns (5, [103][104][105].…”