. An element (such as a tree) that contributes to evapotranspiration can be called an evapotranspirator. Potential evapotranspiration (PET) is a representation of the environmental demand for evapotranspiration and represents the evapotranspiration rate of a short green crop, completely shading the ground, of uniform height and with adequate water status in the soil profile. It is a reflection of the energy available to evaporate water, and of the wind available to transport the water vapour fro… (More on Evapotranspiration)