Glossary
Transpiration
The release of water vapor from plants, mainly through tiny pores (stomata) in their leaves. It is biologically controlled water loss from vegetation, distinct from direct evaporation off an open water surface.
Transpiration is relevant when living covers (such as duckweed or water lilies) are used over water, because the plants themselves return some water to the atmosphere. Combined with evaporation from soil and water surfaces, it forms evapotranspiration.