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The photosynthesis – photon irradiance (PE) response curve is widely used to characterise photoacclimation through changes in light-harvesting pigment composition. Within this context, the P in PE is generally taken to represent mass-specific photosynthesis normalised to Chl a with units of g C (g Chl a)-1 h‑1, for example, while the E represents photon irradiance between 400 and 700 nm (PAR), with units of µmol photons m-2 s‑1.
As an alternative to the standard PE curve approach, chlorophyll fluorometer-based systems are increasingly being used to run so-called rapid light curves (RLCs) or fluorescence light curve (FLCs). These curves can provide relative values of photosynthesis, calculated as PAR x Fq'/Fm' (where Fq'/Fm' provides an estimate of the photon yield of PSII photochemistry, fPSII).
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Within FastPro8, plots of relative photosynthesis (rP) against PAR can be generated in real time from the FLC data generated by the combination of FastOcean and FastAct. The integral curve fitting process used to analyse rPE data generates values for the widely used parameters, a (initial slope), PM (maximum value of P along the curve) and EK (the inflection point, calculated as PM /a).
The values from the rPE fitting process, plus a number of fluorescence parameters derived from analysis of the underlying FRR data, can be shown within the same plot. In the example below, the rPE data are shown with one of the three curve fit options. Details of the curve fitting process are provided within the FastPro8 handbook, which can be found on our downloads page (go to FastPro8 GUI). This includes the FastPro8 GUI (with sample files). The FastPro8 handbook includes a detailed description of all of our FRR-based sensors and systems.
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