Mutually reinforcing and transpiration-dependent propagation of H2O2 and variation potential in plants revealed by fiber organic electrochemical transistors.

Plants use hydrogen peroxide (H₂O₂) and variation potential (VP) waves as well as chemical transport by transpiration-driven xylem flow to facilitate cell signaling, cell-to-cell communication, and adaptation to environmental stresses. The underlying mechanisms and complex interplay among H₂O₂, VP, and transpiration are not clearly understood because of the lack of bioengineering tools for continuous in planta monitoring of the dynamic biological processes. Here, we tackle the challenge by developing microfiber-shaped organic electrochemical transistors (fOECTs) that can be threaded into the plants. The sensorized microfiber revealed that both H₂O₂ and VP waves propagate faster toward the leaves than toward the roots because of the directional long-distance transport of H₂O₂ in the xylem. In addition, the revealed interplays among VP, H₂O₂, and xylem flow strongly suggest a transpiration- and intensity-dependent H₂O₂-VP mutual-reinforcing propagation mechanism. The microfiber electronics offer a versatile platform for the in situ study of dynamic physiological processes in plants with high temporospatial resolution.