Notes on Water Use Efficiency Water use efficiency of plants, also called transpiration efficiency (TE) refers to the amount of water transpired per unit biomass produced by the plant. It is easy to measure for a particular situation if plants are grown in pots and direct evaporation from the pot minimized, just measuring pot weight, assuming that changes are mainly due to transpiration ( a good assumption) and harvesting biomass. Then you will have Biomass/water transpired or TE. The TE is highly influenced by environmental variables but particularly by vapor pressure deficit in the atmosphere (VPD) and by CO2 concentration. To compare results with other determinations of TE you can normalize your values by VPD and CO2 concentration in the atmosphere. As you can see from the previous paragraph you do not need to maintain a constant soil water content to measure TE since what you are really interested in is water loss by transpiration. Of course you can measure TE under well irriga
