Potential transpiration

From Glossary of Meteorology

potential transpiration

The water loss, often expressed as a rate of flux, by a plant (or vegetated surface) when soil water is not limiting.

Usually determined empirically for a plant or vegetation type and referenced to evaporation from a class-A evaporation pan. Potential transpiration may exceed pan evaporation (soybean at peak vegetative stage is about 105% of pan).
See evapotranspiration.