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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 ]
Potential evapotranspiration is expressed in terms of a depth of water or soil moisture percentage. If the actual evapotranspiration is considered the net result of atmospheric demand for moisture from a surface and the ability of the surface to supply moisture, then PET is a measure of the demand side (also called evaporative demand).
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 ...
The water cycle (or hydrologic cycle or hydrological cycle), is a biogeochemical cycle that involves the continuous movement of water on, above and below the surface of the Earth. The mass of water on Earth remains fairly constant over time. However, the partitioning of the water into the major reservoirs of ice, fresh water, salt water and ...
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).
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]
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 ...
Crop coefficients are properties of plants used in predicting evapotranspiration (ET). The most basic crop coefficient, Kc, is simply the ratio of ET observed for the crop studied over that observed for the well calibrated reference crop under the same conditions. Potential evapotranspiration (PET), is the evaporation and transpiration that ...