An apparatus (1) is used to examine or monitor the state or state of health of plants (2) with the aid of a bipolar electrode (4) which uses its at least two different poles (5) to measure corresponding potentials of the plant and supply them to a detector and/or memory (7), in particular via an amplifier (9), with the result that conclusions regarding the state of, or the possible damage to, a plant (2) can be drawn from changes in the electrical signals and can ensure remedial action.