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]

Farlex Partner Medical Dictionary © Farlex 2012

transpiration

(trăn′spə-rā′shən)

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]

Medical Dictionary for the Health Professions and Nursing © Farlex 2012

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:

(a) the Water Vapour Pressure at the MESOPHYLL cell surface inside the leaf. The evaporating surface is saturated and will have a VAPOUR PRESSURE (WVP_satn) that is highly affected by ambient temperature. For example, at 20 °C the WVP_satn = 2.34 kPa, at 10 °C the WVP_satn = 1.23 kPa.
(b) the Water Vapour Pressure in the outside air (WVP_a i_r ), the maximum value being equal to WVP_satn 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 WVP_satn and WVP_air; i.e:WVPdiff= WVP_satn - WVP_air Thus the greater the WVP_di ff value, the greater the diffusion gradient and the higher the transpiration rate.
(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 WVP_a i_r 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.
(d) the stomatal and leaf structure, which are modified in some XEROPHYTES to reduce transpiration rates.
(e) a constant supply of water from the roots.

Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005

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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.

Relationship between root exudation of organic carbon and physiological variables of irrigated rice cultivars/ Relacao entre exsudacao radicular de carbono organico e variaveis fisiologicas de cultivares de arroz irrigado

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.

Acoustic emissions from transpiring plants--new results and conclusions

Increasing irrigation water salinity linearly affected transpiration in soybean plants in the absence of bovine biofertilizer (Figure 2A).

Irrigation with saline water in soybean (Glycine max (L.) Merr.) in a soil with bovine biofertilizer/Irrigacao com agua salina na soja (Glycine max L.) em solo com biofertilizante bovino

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.

Exploring the Potential of Quinoa Accessions for Salt Tolerance in Soilless Culture

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).

Gas exchange in different varieties of banana Prata in semi-arid environment/Trocas gasosas em diferentes cultivares de bananeiras tipo Prata em ambiente semiarido

(2000) found that the 'A' genome chromosomes of wheat carry genes that control high net photosynthesis rate, water use efficiency and below transpiration rate.

PHOTOSYNTHETIC PERFORMANCE IN PLOIDY LEVELS AND AMPHYPLOIDS OF WHEAT DURING DEVELOPMENTAL STAGES

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.

Field management model now better, faster. (Notebook)

The total water loss due to transpiration and evaporation is called evapotranspiration.

Chapter 8: Water conservation

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.

ARE HIGH ELEVATIONS IN TROPICAL MOUNTAINS ARID ENVIRONMENTS FOR PLANTS?

Low aphid infestation significantly increased photosynthetic factors except for transpiration rate.

Effect of Aphid Infestation on Photosynthesis, Growth and Yield of Brassica carinata A. Braun

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].

Effects of rice straw mulch on the diurnal leaf gaseous exchange and growth development of aerobic rice MRQ74 and MR253