High-Resolution Imaging of Plant Delayed Luminescence

Delayed luminescence (DL) is a quantized signal that is characteristic of photoexcited molecules entering a relaxed state. Studying DL provides critical insight into photophysical mechanisms via analysis of specific spatiotemporal dynamics. In this study, we developed a high-sensitivity DL imaging system using a quantitative scientific complementary metal-oxide-semiconductor (qCMOS) camera and a single-photon counting resolution. By optimizing the optical architecture and signal processing algorithms together, we achieved full-field spatiotemporal DL imaging at megapixel resolution (i.e., 2304 $\times$ 4096 pixels). Key findings include the following: (1) we observed spatial heterogeneity in DL intensity across the leaves of Arabidopsis thaliana, with stronger signals detected in veins and at sites of mechanical injury; (2) species-specific DL responses occurred in response to oxidative stress, with Hydrocotyle vulgaris and Ginkgo biloba showing enhanced central DL activity; (3) Excitation using white light induced maximum DL intensity, while red and blue light differentially modulated decay kinetics. Finally, we develop a two-level quantum model that links DL dynamics to the populations of excited-state electrons, thereby developing a theoretical framework for future photophysical research. Overall, this work may help future studies of plant phenotyping under stress and light environment optimization.