Installing the Bryophyte Chamber

The Bryophyte Chamber (6800-24) is used to measure CO2and H2O gas exchange from mosses, hornworts, liverworts,and lichens. The chamber holds sample material on wiremesh or in a shallow well during the measurement. It fea-tures a clear Propafilm™ top for measurements under ambi-ent lighting conditions. It is compatible with the Large LightSource for measurements under controlled lighting with anycombination of red, green, blue, and white light. This doc-ument provides installation instructions for the chamber.

Description Part Number

Mesh Screen (1) 197-09025Short Risers (4) 170-04629Short Riser Screws; M3-8 (4) 150-13642Tall Risers (4) 170-16503Tall Riser Screws; M3-25 (4) 150-15454Chamber Bottom Plate (1) 9868-550Chamber Bottom Screws; M4-12 (4) 150-14476Flat Washers; #4 5/16 (8) 167-00155

Detach the chamber from the headSix screws will be removed to detach a chamber — two onthe connector cover, two on the latch mechanism, and twothat hold the chamber to the head. This requires PhillipsPH1 and PH2 screwdrivers, which are in the spares kit. Suit-able screwdrivers are available from most department stores.

Caution: Power off the instrument before following theseprocedures.

1 Using the PH1 Phillips screwdriver, remove the twocover screws and the connector cover from the bot-tom of the head.

2 Unplug the cables from the cable bulkhead (i.e.,LI-190R, leaf temperature thermocouple, and lightsource).

3 Position the chamber latch in the parked position andremove the two latch screws with the PH2 Phillipsscrewdriver.

4 Using a PH2 Phillips screwdriver, loosen both of thecaptive chamber screws until the chamber is free ofthe head.

5 Separate the chamber from the head.

Warning: Do not attempt to operate the mixing fanwithout a chamber in place.

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Installation Guide

While the chamber is removed from the head, inspect the AirFilters and Dust Trap. Clear any dust or debris before attachinga chamber.

Installing the Bryophyte Chamber

1 Install the chamber adapter.

2 Tighten the screws snugly—until they are tight andthen just a little bit more. Reinstall the connectorcover.

3 Remove the chamber top. It lifts off of the chamber.

4 Prepare the chamber bottom for a sample.

There are three options for loading the sample: A) on thescreen with short risers, B) on the screen with tall risers,or C) in a well. The well is on one side of the chamberbottom; the screens mount to the other side. Install thechamber bottom in the orientation that you prefer.

Figure 1. Chamber bottom configurations. A shows theshort risers; B shows the tall risers; and C shows thewell.

5 Power on the LI-6800, if it is not already on, andverify that the instrument recognizes the 6800-24chamber under Start Up > Configuration > Chamber Setup.

6 Choose whether to compute Area-based fluxes or Mass-based fluxes.

7 Press the chamber top into the opening and run theleak test (Start Up > System Tests > Chamber Leak).

Loading a sampleRemove a sample from the substrate using a knife or cookiecutter. You can place a sample on the screen or in the well. Ifyou're computing fluxes on the basis of mass, you'll need toweigh each sample and make a record of the mass. For area-based fluxes, you'll need to determine the sample area. Afterloading the sample, press the chamber top onto the chamber.

Making a measurementBelow we offer some basic settings that will work for a typ-ical measurement.

1 Set the Environment controls.

Flow: Set Flow: On; Pump speed: Auto; Flow rate: 700µmol s-1; Press Valve: 0.0 kPa

H2O: Set H2O: On; RH_air: 50%

CO2: Set CO2 injector: On; Soda Lime: Scrub Auto; TapCO2_s and enter a setpoint of 400 µmol mol-1

Fan: Set Mixing fan: On; Fan Speed: 10,000 rpm

Temperatures: Check the temperatures to see theircurrent values

2 Set the Constants.

Under Constants > Gas Exchange, enter the Area or Mass.3 Configure Logging options.

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Configure the Match Options and Logging Options as desired.Check Prompt on (manual) log, which will open a promptwhen you press the Log button, where you can enter theweight or area.

4 Open a log file.

5 Tap the Log button to record a measurement.

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