A structural unit for plant nourishment and air conditioning premises has a circuit (2) for water having an upper overflow vessel (16) and a lower collector (12) in which a support (15) extends between the vessels (16, 12), the supporting surface of which lies inside the cylindrical collector (12), has a cross-section which continuously tapers towards the upper side and over the outside of which the water from the overflow vessel (16) is intended to flow. The collector (12) is connected to a circular container (1) for plants in the manner of communicating vessels so that the liquid level inside the collector (12) and hence that inside the container (1) can be controlled by a control system (3). In addition, the circuit (2) has facilities for the control of the water temperature. Owing especially to the monitoring and control of the liquid level inside the container (1), a unit is provided which, in addition to the easy care of plants, makes a considerable contribution towards the air conditioning of the premises through the film-like outer flow over the support (15).
