Dual-Target Fluorescent Imaging of Hg ²⁺ and Cell Membrane Stress in Live Plants

Monitoring mercury ion (Hg²⁺) accumulation and its phytotoxicity in plants requires analytical methods that provide both spatial and functional information beyond simple destructive quantification. We report HBTD-Hg, a dual-target fluorescent probe engineered to anchor to the cell membrane and exhibit a selective fluorescence turn-on response to Hg²⁺. This design enables simultaneous in situ imaging of Hg²⁺ distribution and real-time assessment of membrane integrity in live plant tissues. The probe quantifies Hg²⁺ with a detection limit of 49.7 nM. Importantly, it allows for the nondestructive tracking of Hg²⁺ uptake dynamics directly through leaf imaging. Furthermore, it directly visualizes the ensuing Hg²⁺ induced loss of cellular membrane integrity, including distinct vesiculation. This work provides a versatile tool for the real-time assessment of heavy metal stress, effectively linking environmental ion detection to observable cytological damage in plants.