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 ?
Foliar application of SA (100 ppm) and L-TRP (15 ppm) may regulate stomatal openings and reduce transpirational water loss under drought conditions enabling the plants to maintain turgor, carry on photosynthesis and be productive under water deficit conditions.
Such vessels can be correlated with high transpirational demands, which in turn are related to the massive size of leaves (which in turn are correlated with infrequency of branching in palms).
transpirational pull: Main phenomenon driving the flow of sap in the xylem tissues of large plants.
This upward movement occurs because of transpirational pull created by the evaporation of water from the leaves.
Abscission of lower leaves and reduced leaflet size in water-stressed senna plants caused >75% reduction in total transpirational surface area.
A more detailed theoretical analysis of plant transpiration, however, has raised doubt as to whether high elevations are environments with rather low transpirational demand simply because of their low temperatures.
This practice also helps control weeds which reduces transpirational losses of water.
However, the ratio of root to leaf biomass decreased sharply in plants grown at moderate and low light, which accords with decreased transpirational demands (Bjorkman et al.
Some nutrients are drawn to root surfaces in the mass flow of water immediately after rainfall, and some are lifted to the canopy by transpirational pull.
The area of transpiring leaves of a vineyard is typically smaller than the transpirational area of a reference grass crop.
2] uptake, transpirational water loss and simulated water use efficiency can either decrease or increase with altitude depending on the mountain system (Figs.