Dissecting the Contributions to Non-photochemical Quenching in a Land Plant Under Fluctuating Light

To safely dissipate excess excitation energy, photosynthetic organisms have evolved multiple photoprotection mechanisms. These mechanisms involve various molecular players functioning on overlapping timescales from seconds to days, making it challenging to isolate and quantify their individual kinetics. In this study, we perform whole-leaf chlorophyll fluorescence lifetime and xanthophyll concentration measurements on wild-type and various newly characterized non-photochemical quenching mutants of Nicotiana benthamiana, an allotetraploid vascular land plant. Based on these measurements, we construct a fluorescence lifetime-based quantitative kinetic model that disentangles individual photoprotection components and, when integrated additively, accurately predicts wild-type and mutant quenching/recovery behaviors under various light-dark regimes. Additionally, the model quantifies the per-molecule quenching efficiencies of various xanthophylls and the contributions of six quenching pathways across different mutants. It also suggests that enhancing VDE, ZEP, and PsbS expression improves overall quenching efficiency, aligning with previous studies and supporting translational efforts to optimize photoprotection and enhance crop yields under dynamic light environments.