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Gas exchange measurement

Carl Otto Ottosen: University of Aarhus

The IRGA systems (CIRAS-2, Licor, ADC, Walz) with the relevant leaf cuvettes can be used for the measurement of gas exchange parameters. CO2 level and temperature should be set to the reference CO2 and temperature set to to a fixed level (400 ppm CO2, 20°C) between measurements (suggest equal to the setpoints for the growth temperature).

  1. Snap shot measurements:

To get an impression of the steady state photosynthesis a simple static measurement of the cultivars (4-5 leaves per cultivar)

  1. Light response measurements:

The light response might reveal differences in capacity but are rather time consuming as 3-4 measurements per genotype is needed and the time between measurement requires steady state for both Pn and gs

Light response curve of each cultivar is made by using a series of photosynthetic photon flux density (PPFD), 300 (or the just above the ambient light level), 200, 100, 50, 0, 300, 400, 600, 900 and 1200 (or higher) at 24 °C, 60% RH and 400 ppm CO2. Values need to be taken from means of three replications.  It is possible to make curve fits in excel to get the parameters.