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Transpiration rates of plants can be measured by a number of techniques, including potometers, lysimeters, porometers, photosynthesis systems and thermometric sap flow sensors. Isotope measurements indicate transpiration is the larger component of evapotranspiration . [ 11 ]
Potometer. A potometer' (from Greek ποτό = drunken, and μέτρο = measure), sometimes known as transpirometer, is a device used for measuring the rate of water uptake of a leafy shoot which is almost equal to the water lost through transpiration. The causes of water uptake are photosynthesis and transpiration. [1]
Definition. Evapotranspiration is defined as: "The combined processes through which water is transferred to the atmosphere from open water and ice surfaces, bare soil and vegetation that make up the Earth’s surface." [ 2 ]: 2908. Evapotranspiration is a combination of evaporation and transpiration, measured in order to better understand crop ...
Stomatal conductance, usually measured in mmol m −2 s −1 by a porometer, estimates the rate of gas exchange (i.e., carbon dioxide uptake) and transpiration (i.e., water loss as water vapor) through the leaf stomata as determined by the degree of stomatal aperture (and therefore the physical resistances to the movement of gases between the air and the interior of the leaf).
Potential evapotranspiration (PET) or potential evaporation (PE) is the amount of water that would be evaporated and transpired by a specific crop, soil or ecosystem if there was sufficient water available. It is a reflection of the energy available to evaporate or transpire water, and of the wind available to transport the water vapor from the ...
The corresponding equation is: ET0 = Reference evapotranspiration, Water volume evapotranspired (mm day −1) Δ = Rate of change of saturation specific humidity with air temperature. (Pa K −1) Rn = Net irradiance (MJ m −2 day −1), the external source of energy flux. G = Ground heat flux (MJ m −2 day −1), usually equivalent to zero on ...
Water-use efficiency (WUE) refers to the ratio of plant biomass to water lost by transpiration, can be defined either at the leaf, at the whole plant or a population/stand/field level: leaf level : photosynthetic water-use efficiency (also called instantaneous water-use efficiency WUE inst), which is defined as the ratio of the rate of net CO 2 ...
Transpiration stream. Overview of transpiration. 1-Water is passively transported into the roots and then into the xylem. 2-The forces of cohesion and adhesion cause the water molecules to form a column in the xylem. 3- Water moves from the xylem into the mesophyll cells, evaporates from their surfaces and leaves the plant by diffusion through ...