Water transport within the soil-plant-atmosphere continuum

Because water is generally free to move across the plant-soil, soil-atmosphere, and plant-atmosphere interfaces it is necessary and desirable to view the water transfer system in the three domains of soil, plant, and atmosphere as a whole. . . it must be pointed out that, as well as serving as a vehicle for water transfer, the SPAC is also a region of energy transfer.John R. Philip (1966)