Dual-Target Fluorescent Imaging of Hg2+ 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.