This is with the PAR sensor being set to 1000. The LICOR has been used on multiple plant species and leaf types with the values ranging between -0.7 and -2.2. The plants are located in a humid environment that is approximately 100 degrees Fahrenheit. Any help is much appreciated.
There may be several reasons for negative values. You go through the LICOR LI-6400xt Manual. Try these steps 1. Check flow (Zero)2. IRGA zero, 3. If using mixer (Check CO2, H20 Zero)4. Q leaf (whether it is giving the exact light)5. Check Tleaf 6. Then set reference CO2 7. check there is lo leakage in system 8. check the desiccant 9. Matching valves are working, 10. Mixing fan is working Like that. These are general remedies.
Other commons mistakes are forgetting to change the scrub tube setting after testing the IRGAs’ zero, forget to turn on the LED source? correct leaf area? Is the flow rate OK? It is typically between 200 and 700 μmol s-1.
Hayati Akman, it was a cloudy day when the plants were tested and they are still stressed from being replanted the other week. I suspect these are the causes for our results. Thank you so much.
Ashish Chaturvedi, all of these steps were done and similar results were obtained from different users with two separate LICOR machines. We will certainly follow all of these steps with future use of the LICOR, however. Thank you!
Kelsie, as you said that the measurement were performed on cloudy day, and even the stage, plant species and any other environmental stress may affect these traits.
There could be many reasons, a) whether you fixed the CO2 cylinder (steel) or open bottle? It might be easier to address if you share the excel output or you may confirm the CO2S and CO2R in Excel data-sheet. Fix the flow around 400 μmol s-1 and match both the CO2S and CO2R. b) Check the color of both the scrub and soda connected bottles, you may need to change and also check their level. Good luck.
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