An overview of analytical methods for detecting endogenous hydrogen sulfide (H₂S) in plants

The significance of hydrogen sulfide (H₂S) as a crucial gasotransmitter has been shown extensively in plants, and endogenous H₂S is often modulated to activate H₂S signaling when plants respond to numerous developmental and environmental cues. Consequently, elucidating the H₂S physiological concentrations and the H₂S generation intensity of plants is key to understanding the activation mechanism of H₂S signaling, which has attracted increasing attention. Currently, a variety of reaction-based methods have been reported for monitoring H₂S concentration in vivo and in vitro. In this review, we summarize and describe in detail several methods for quantifying and bioimaging endogenous H₂S in plants systems, mainly the spectrophotometer-dependent methylene blue (MB) method and fluorescence probes, including the reaction mechanisms, design strategies, response principles, and application details. Moreover, we also summarize the advantages and disadvantages of these methods as well as the research scenarios in which they are applicable. We expect that this review will provide some guidelines on the selection of methods for H₂S sensing and the comprehensive investigations into H₂S signaling in plants.