Growing Fiber Sensors Enable Continuous In Vivo Monitoring of Plant Hormones.

Plant stress during growth, caused by extreme environments and biotic attacks, threatens global biodiversity and crop production, necessitating urgent elucidation of plant adaptation mechanisms. Endogenous hormones of plant growth serve as master regulators and earliest indicators of stress adaptation, making it crucial to monitor their dynamics continuously. However, existing methods, including chromatography and electrochemical probes, fail because of their mismatch with the irreversible and plastic nature of plant growth. Here, we unexpectedly find a growing fiber sensor based on an electrode consisting of a dynamic polymer network infiltrated with liquid metal, termed metalgel. The sensor undergoes irreversible elongation ∼up to 10 times its original length under just 3.2 kPa tensile stress, at least 2 orders of magnitude lower than existing electronic conductive systems, thus achieving synchronous deformation with plant growth without inducing mechanical damage or hormonal disturbances. Hormone dynamics and relevant signaling pathways during plant growth in response to pathogen infection, salt stress, and even extreme ultraviolet radiation are thus revealed by the sensor. This work provides quantitative insights into plant stress resilience mechanisms and offers a feasible route to alleviate the food and ecological crises.