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

(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.
References in periodicals archive ?
With regard to the transpiration rate, the 'BRS Pampa' cultivar presented the highest value in both readings whereas the 'IRGA 421' the lowest one together with the cultivar 'Embrapa 130' in the 1st reading, and the cultivars 'Koshihikari', 'IRGA 422', 'BRS Querencia' (early cycle), and 'IAS Formosa' in the 2nd reading.
The advantage of detecting AE from a living leaf is that the signal generation occurs in the immediate area of the site of transpiration. Although we applied a mild medical contact gel, the mesophyll, in the contact area became necrotic very soon after contact was made.
Increasing irrigation water salinity linearly affected transpiration in soybean plants in the absence of bovine biofertilizer (Figure 2A).
For each transition, the transpiration flow can be modeled many ways.
Another parameter was transpiration rate of plants, in which maximum transpiration rate was observed in non-saline conditions in genotype Q9 and then it decreased significantly (p <0.05) at each level.
The physiological variables, leaf temperature ([T.sub.leaf]), transpiration rate (E) and instantaneous efficiency of water use (A/E) varied with the cultivar regardless of the month and reading time (Table 1).
(2000) found that the 'A' genome chromosomes of wheat carry genes that control high net photosynthesis rate, water use efficiency and below transpiration rate.
An Agricultural Research Service (ARS) Agricultural Engineer, Simon van Donk and his colleagues, have updated the computer model so it now simulates the effects of a mulch layer on soil water content and temperature, soil water evaporation, and crop transpiration. In addition to adding the mulch option, the researchers adjusted some of the mathematical equation in the model, making it faster.
The total water loss due to transpiration and evaporation is called evapotranspiration.
This paper tests the hypotheses (1) that aridity (potential transpiration [E.sub.p]/rainfall P) in tropical alpine environments can be high despite low temperatures, and (2) that aridity in tropical alpine environments may be correlated with scleromorphic habit.
Low aphid infestation significantly increased photosynthetic factors except for transpiration rate.
Mulching with straw has been reported to improve i] crop water use efficiency [11-12], ii] root biomass [13], root length density and root weight density [14], iii] stomatal conductance, transpiration, and photosynthesis characteristics [13] in addition to iv] grain yield [15].