1. the loss of water from plant tissues in the form of vapor.
This is a water cycle diagram including transpiration. Source:http://www.nps.gov
This image demonstrates the process of transpiration in a plant.
Transpiration is the process by which water vapor escapes from living plants and enters the atmosphere. It includes water which has transpired through leaf stomata, as well as intercepted water which has re-evaporated. When the soil is covered by a growing crop, transpiration geatly exceeds evaporation.