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Photosynthesis and cellular respiration are distinct processes, as they take place through different sequences of chemical reactions and in different cellular compartments (cellular respiration in mitochondria). [15] [16] The general equation for photosynthesis as first proposed by Cornelis van Niel is: [17]
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 ]
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]
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).
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 carbon assimilation (photosynthesis) to the rate of transpiration or stomatal conductance, [1] then called intrinsic water-use efficiency [2] (iWUE or W i)
Since photosynthesis, transpiration and stomatal conductance are an integral part of basic plant physiology, estimates of these parameters can be used to investigate numerous aspects of plant biology. The plant-scientific community has generally accepted photosynthetic systems as reliable and accurate tools to assist research.
Transpiration: the movement of water from root systems, through a plant, and exit into the air as water vapor. This exit occurs through stomata in the plant. Rate of transpiration can be influenced by factors including plant type, soil type, weather conditions and water content, and also cultivation practices. [ 6 ] :
Of the 150 kWh falling on the crown, 1% is used for photosynthesis, 10% reflected as light energy, 5 to 10% as sensible heat with the remaining 79 to 84% entering the process of transpiration. [3] If a larger tree has a sufficient water supply, it can evaporate more than 100 L of water a day.