An electrical analogue of evaporation from, and flow of water in plants.

The currents generated in the analogue circuit represent vapour loss from leaves, heat loss from leaves, and liquid flow in plant and soil. The plant and soil resistances are defined in such a way that they are consistent with the resistances to transport of vapour in the atmosphere and there is continuity of potential at the analogue liquid: air interface in the leaves. The action of the environment on plant water movement is treated as an application of Thévenin's theorem of electric circuits.