transpiration


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transpiration

 [trans″pĭ-ra´shun]
discharge of air, vapor, or sweat through the skin.

tran·spi·ra·tion

(tran'spī-rā'shŭn),
Passage of watery vapor through the skin or any membrane.
See also: insensible perspiration.
[trans- + L. spiro, pp. -atus, to breathe]

transpiration

/tran·spi·ra·tion/ (tran″spĭ-ra´shun) discharge of air, vapor, or sweat through the skin.

transpiration

(trăn′spə-rā′shən)
n.
The act or process of transpiring, especially through the stomata of plant tissue or the pores of the skin.

tran′spi·ra′tion·al adj.

tran·spi·ra·tion

(trans'pir-ā'shŭn)
Passage of water vapor through the skin or any membrane.
See also: insensible perspiration
[trans- + L. spiro, pp. -atus, to breathe]

transpiration

the loss of water vapour from the inside of a leaf to the outside atmosphere, via STOMATA and LENTICELS. Transpiration exerts a considerable upward pressure in the stem and is thought to be part of the explanation of how water ascends from roots to leaves.

The rate at which transpiration proceeds depends upon several physical factors:

  1. (a) the Water Vapour Pressure at the MESOPHYLL cell surface inside the leaf. The evaporating surface is saturated and will have a VAPOUR PRESSURE (WVPsatn) that is highly affected by ambient temperature. For example, at 20 °C the WVPsatn = 2.34 kPa, at 10 °C the WVPsatn = 1.23 kPa.
  2. (b) the Water Vapour Pressure in the outside air (WVPa ir ), the maximum value being equal to WVPsatn at that temperature. If there is the same temperature inside and outside the leaf, the rate of flow of water vapour between the surface of the mesophyll cell and the outside is the difference between WVPsatn and WVPair; i.e:WVPdiff= WVPsatn - WVPair Thus the greater the WVPdi ff value, the greater the diffusion gradient and the higher the transpiration rate.
  3. (c) the size and number of stomatal pores per unit area of a leaf. The smaller the pore diameter, the greater the resistance to water vapour diffusion. The presence of'vapour shells’ over each stoma creates a boundary layer of high Water Vapour Pressure in still air, which will slow down the transpiration rate since it increases the WVPa ir value. This effect is most important when the pore diameter is large. In moving air, the vapour shells cannot form and thus transpiration rates increase.
  4. (d) the stomatal and leaf structure, which are modified in some XEROPHYTES to reduce transpiration rates.
  5. (e) a constant supply of water from the roots.

transpiration

passage of water vapour through any membrane

transpiration

discharge of air, vapor or sweat through the skin.
References in periodicals archive ?
Brachiaria plants grown under full sunlight exhibited a higher transpiration rate (E) than plants grown in plots where intercropping systems were adopted.
This study aimed to adjust the sap flux equation proposed by Granier to African Mahogany and relate its transpiration to leaf area and evapotranspiration.
As salinity is the main reason for drop in gas exchange, it is also responsible for the decline in transpiration of quinoa plants (Sanchez et al.
The transpiration rates evaluated in 'prata' type banana differ between times in every evaluation month, regardless of the cultivar (Table 2), with the occurrence of lower values in the morning and of higher values in the afternoon at 78.
01; Table 2) for stomatal conductance (gs), net photosynthesis rate (Pn), transpiration rate (Tr), substomatal CO2 concentration (Ci) and water use efficiency (WUE) throughout the three developmental phases, at tillering stage (Til), early grain filling stage (EGF) and late grain filling stage (LGF).
Infestation of aphids reduced the photosynthetic parameters except transpiration rate.
This differs from the findings of others; stomatal conductance, transpiration, and photosynthesis in rice under non-flooded mulching cultivation were reported to be higher under mulch treatment in comparison to those without soil cover [13] while mulching was found to increase leaf transpiration in wheat crop [53].
The regulation mechanism of stomatal conductance did not result in corresponding alterations in transpiration because E did not decrease according to the lower values of gs.
Respecting new insights from research, it is a concern that nighttime transpiration has not been considered in small- scale evapotranspiration models (irrigation scheduling of crops), nor for large-scale models (catchments and forest water-use estimations).
Controlling the air temperature and relative humidity therefore also controls the amount of water that can be recovered from transpiration and the amount of energy needed to condense the water vapor.
The transpiration of water is an energetic process, so the more transpiration, the more heat is removed from the environment.
C'est pourquoi il est important de compenser les pertes en buvant au moins 1 litre d'eau par jour Mais dans certains cas, la production de sueur peut atteindre voire depasser dix litres par jour lors d'une transpiration excessive survenant au cours de l'hypertrichose.