Transpiration 54846 224795299 2008-07-10T13:18:01Z 151.203.6.33 deleted "hi" from beginning of entry {{dablink|Transpiration may also refer to [[sweating]] and [[hyperhydrosis]].}} '''Transpiration''' is the [[evaporation]] of water from the aerial parts of [[plant]]s, especially [[leaf|leaves]] but also [[Plant stem|stem]]s, [[flower]]s and [[root]]s. Leaf transpiration occurs through [[stomata]], and can be thought of as a necessary "cost" associated with the opening of stomata to allow the diffusion of [[carbon dioxide]] gas from the air for [[photosynthesis]]. Transpiration also cools plants and enables [[mass flow]] of [[Plant nutrition|mineral nutrients]] and water from [[root]]s to [[shoot]]s. Mass flow is caused by the decrease in hydrostatic (water) pressure in the upper parts of the plants due to the [[diffusion]] of water out of [[stomata]] into the [[Earth's atmosphere|atmosphere]]. Water is absorbed at the roots by [[osmosis]], and any dissolved mineral nutrients travel with it through the [[xylem]]. The rate of transpiration is directly related to the degree of stomatal opening, and to the evaporative demand of the atmosphere surrounding the leaf. The amount of water lost by a plant depends on its size, along with the surrounding [[light]] intensity, [[temperature]], [[humidity]], and [[wind]] speed (all of which influence evaporative demand). [[Soil]] [[water]] supply and soil temperature can influence stomatal opening, and thus transpiration rate. A fully grown tree may lose several hundred [[gallon]]s (a few cubic meters) of water through its leaves on a hot, dry day. About 90% of the water that enters a plant's roots is used for this process. The '''transpiration ratio''' is the ratio of the mass of water transpired to the mass of dry matter produced; the transpiration ratio of [[Crop (agriculture)|crops]] tends to fall between 200 and 1000 (i.e., crop plants transpire 200 to 1000 kg of water for every kg of dry matter produced) {{Harv|Martin|Leonard|Stamp|1976|p=81}}. Transpiration rate of plants can be measured by a number of techniques, including [[potometer]]s, [[lysimeter]]s, porometers, and heat balance sap flow gauges. [[Desert]] plants and [[conifer]]s have specially adapted structures, such as thick cuticles, reduced leaf areas, sunken stomata and hairs to reduce transpiration and conserve water. Many [[cactus|cacti]] conduct photosynthesis in [[succulent]] stems, rather than leaves, so the surface area of the shoot is very low. Many desert plants have a special type of [[photosynthesis]], termed [[Crassulacean acid metabolism]] or CAM photosynthesis in which the stomata are closed during the day and open at night when transpiration will be lower. == See also == *[[Evaporation]] *[[Active Transport]] *[[Osmosis]] *[[Hyperhydrosis]] *[[Transpirational pull]] <!-- --~~~~ --> == References == * [http://extension.oregonstate.edu/mg/botany/transpir.html A description of transpiration, including a short animation illustrating the process] * {{Harvard reference | Surname1=Martin | Given1=J. | Surname2=Leonard | Given2=W. | Surname3=Stamp | Given3=D. | Title=Principles of Field Crop Production (Third Edition) | Publisher=New York: Macmillan Publishing Co., Inc. | Year=1976 | ID=ISBN 0-02-376720-0}} == External links == *[http://www.ramin.com.au/creekcare/trees.shtml Transpiration by Trees] {{-}} {{Botany}} [[Category:Hydrology]] [[Category:Plant physiology]] [[bg:Транспирация]] [[ca:Transpiració vegetal]] [[cs:Transpirace]] [[da:Transpiration (botanik)]] [[de:Transpiration]] [[et:Transpiratsioon]] [[es:Transpiración]] [[fa:تعرق]] [[fr:Transpiration végétale]] [[id:Transpirasi]] [[it:Traspirazione]] [[he:דיות]] [[lt:Transpiracija]] [[hu:Transpiráció]] [[mk:Транспирација]] [[nl:Transpiratie (hydrologie)]] [[ja:蒸散]] [[no:Transpirasjon]] [[pl:Transpiracja]] [[pt:Transpiração]] [[ru:Транспирация]] [[simple:Transpiration]] [[sk:Transpirácia]] [[sl:Transpiracija]] [[sr:Транспирација]] [[fi:Transpiraatio]] [[sv:Transpiration]] [[tr:Transpirasyon]] [[uk:Транспірація]] [[zh:蒸腾作用]]