A term that combines the processes of evaporation and transpiration associated with plant growth. Evaporation applies to water vapour that evaporates directly from the soil or where rainfall has fallen on the plant. Transpiration is where water from inside a plant converts to water vapour at the surface of its leaves and stem.
This is water that was taken up by a plant’s roots and carried upwards through the plant bringing vital nutrients from the soil. It is difficult to separately measure the evaporation and transpiration across an area of vegetation and therefore convenient to combine them under one term and measurement. The usual units are mm/day or mm/year making it to compare with rainfall measurements.
