In this paper, we demonstrate in-vivo plant based dehydration sensing using a bio-electrochemical sensor. In-vivo sensing reports on the plant's status as provided by its gene expression, responding to stress. Plant based sensing provides precise, real-time information acquired from the plants themselves; it complements the information provided by ex-vivo sensors sampling the plant's surroundings, e.g. in the soil, or sensors measuring the plant's electrical conductivity. In this paper, we present a method in which the plant's dehydration levels are monitored in real time using in-vivo techniques using the plant as the sensor. In this method, the expression of the β-Dglucuronidase enzyme, expressed under drought conditions, is monitored using its reaction with a substrate, which produces an electrochemically active product. The product is oxidized on the working electrode of a three-electrode electrochemical chip mounted on the leaves of Nicotiana tabacum plants. Electrochemical sensing showed earlier detection compared to other methods, e.g. visual inspection and conductivity measurements.