Unveiling the interplay between methylglyoxal and plant growth under abiotic adversity via a red‐emissive probe operated by a ring‐closure mechanism

Abstract Methylglyoxal (MGO) functions as a key signaling molecule in plants, regulating plant growth, development, and stress responses, particularly under abiotic stress conditions. Despite its recognized importance, direct evidence linking MGO dynamics to plant growth under abiotic stress remains limited. To address this gap, we developed a benzoindole‐derived fluorescent probe BH‐PDN , which employs o‐phenylenediamine as the recognition group to enable sensitive detection of MGO through a specific ring‐closing reaction, accompanied by a pronounced red turn‐on fluorescence response (20.4‐fold enhancement). BH‐PDN exhibited exceptional detection capabilities, including a large Stokes shift (255 nm) and low detection limit (78 nM), allowing fluorescence visualization of exogenous and endogenous MGO‐associated changes in living cells, zebrafish, and Arabidopsis thaliana . Notably, BH‐PDN imaging revealed pronounced increases in MGO‐associated fluorescence in Arabidopsis roots under salt, extreme‐temperature, and drought stress, accompanied by reduced root elongation. These findings support a close association between stress‐associated MGO changes and reduced root elongation. Thus, BH‐PDN serves as a reliable optical window for dissecting the MGO–growth interplay, enabling real‐time interrogation of stress adaptation pathways.