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Indirectly - by measuring the distance the water level drops in the graduated tube over a measured length of time. It is assumed that this is due to the cutting taking in water which in turn is necessary to replace an equal volume of water lost by transpiration. Directly - by measuring the reduction in mass of the potometer over a period of time.
The PI (or photosynthesis-irradiance) curve is a graphical representation of the empirical relationship between solar irradiance and photosynthesis. A derivation of the Michaelis–Menten curve, it shows the generally positive correlation between light intensity and photosynthetic rate. It is a plot of photosynthetic rate as a function of light ...
Photosynthesis systems function by measuring gas exchange of leaves. Atmospheric carbon dioxide is taken up by leaves in the process of photosynthesis, where CO 2 is used to generate sugars in a molecular pathway known as the Calvin cycle. This draw-down of CO 2 induces more atmospheric CO 2 to diffuse through stomata into the air spaces of the ...
CO 2 is commonly measured in μmols/(m 2 /s), parts per million, or volume per million; and H 2 O is commonly measured in mmols/(m 2 /s) or in mbars. By measuring CO 2 assimilation, ΔH 2 O, leaf temperature, barometric pressure, leaf area, and photosynthetically active radiation (PAR), it becomes possible to estimate, "A" or carbon ...
Photosynthetic capacity (A max) is a measure of the maximum rate at which leaves are able to fix carbon during photosynthesis. It is typically measured as the amount of carbon dioxide that is fixed per metre squared per second, for example as μmol m −2 sec −1 .
When measuring the irradiance of PAR, values are expressed using units of energy (W/m 2), which is relevant in energy-balance considerations for photosynthetic organisms. [4] However, photosynthesis is a quantum process and the chemical reactions of photosynthesis are more dependent on the number of photons than the energy contained in the photons.
The following is a breakdown of the energetics of the photosynthesis process from Photosynthesis by Hall and Rao: [6]. Starting with the solar spectrum falling on a leaf, 47% lost due to photons outside the 400–700 nm active range (chlorophyll uses photons between 400 and 700 nm, extracting the energy of one 700 nm photon from each one)
The light absorption spectrum for CO 2 and H 2 O overlap somewhat, therefore, a correction is necessary for reliable CO 2 measuring results. [2] The critical measurement for most plant stress measurements is designated by "A" or carbon assimilation rate. When a plant is under stress, less carbon is assimilated. [3] CO 2 IRGAs are capable of ...