We have the irga Li 6800 and when we set up the equipment for plant C3, with 700 of flow, according to the manual instruction, appear in the display of the irga:
The reference water is very low, lower than that of the sample.
Transpiration gives unreal values of 7 mol for photosynthesis of 14.
We did several procedures recommended by the manual, but they did not solve it.
In the manual it is recommended not to increase the amount of reference water too much, as condensation of water (dew point) may occur.
In the face of these occurrences, we do not know how to proceed.
Please, we would like an orientation on how to eresolve it.
If you can help us, we thank you.
Hello Mary! Reference H2O is typically lower than sample, as the leaf adds water to the chamber. But, yes a transpiration rate (E) of 7 is much too high. What are your H2O_r and H2O_s readings? Are you doing survey measurements or response curves? How long are you waiting between measurements?
The LI-6800 actually protects itself from condensation–it sets a lower H2O setpoint or higher temperature until RH drops below 90%. So you don’t have to worry about setting it too high. We recommend working at an RHCham between 50% and 80%.