A device and a system are for measuring fluid potential in a plant tissue by measuring pressure changes caused due to osmosis of the plant fluid. The measuring device includes a compartment having a ridged body configured for containing an osmoticum. The compartment has at least one opening; at least two selective barrier layers, such as a membrane positioned at least over the openings of the compartment; and at least one pressure sensor configured for detecting changes in pressure of fluid in the compartment. The selective barrier is located for selectively allowing water transfer between the plant fluid and the osmoticum in the compartment. The compartment is configured such that there is a direct contact between the plant fluid and the osmoticum therein via the selective barrier.