Simultaneous and Continuous Monitoring of Plant Bioimpedance and Phytohormones

In this paper, we present a minimally invasive sensor for the assessment of plant health, based on functionalized inter-digitated electrodes decorated with microneedles. The shaft length of the needles is tuned to pierce the cuticle of the leaf to gain access to the mesophyll layer, where the monitoring of bioimpedance and electrochemical detection of salicylic acid, a phytohormone, is possible. A functional coat of molecularly imprinted polymers is utilized to pre-concentrate the phytohormone around the electrodes to achieve a sufficiently low limit of detection of 2.74 μM. We demonstrate the performance of the device for the in situ detection of salicylic acid and monitoring the diurnal cycling of bioimpedance of live plants to identify light stress.