Transpiration is the process in which plants release water back into the atmosphere in the form of water vapor. In simplest terms, transpiration is the evaporation of water from plant leaves. This process occurs from the roots of the plants that carry moisture to the undersides of the leaves and is then released through the pores of the leaves back into the atmosphere. About 10% of the moisture in the atmosphere is released by plants through this process; while the other 90% come from bodies of water.