Agritech and precision agriculture are emerging as key approaches to enhance the sustainability and efficiency of modern farming systems. Among the various techniques proposed to achieve this goal, the direct monitoring of plants through electrical measurements represents a promising and innovative solution. Building on previous work conducted within the same research group, this thesis focuses on the design and development of an autonomous, battery-free, and low-power system capable of assessing plant health status through stem impedance measurements. The main objective of this work is twofold: to achieve complete energetic independence by exploiting solar energy harvesting, and to design and validate an alternative low-cost and low-power measurement architecture that improves upon the traditional relaxation oscillator circuit previously employed.