Transcript Welcome to I.R.G.A. World! • Stands for InfraRed Gas Analyzer, but commonly known as an IRGA • Uses a laser to measure the.

Welcome to I.R.G.A. World!
• Stands for InfraRed Gas Analyzer, but
commonly known as an IRGA
• Uses a laser to measure the concentration of
CO2 and water vapor
• Uses these measurements to calculate
photosynthetic and respiration rates in real
time!
Welcome to IRGA World!!!
Main idea: IRGA function
• Air passing through the machine is always
measured in the analyzer environment.
• Measuring ambient air means the air goes
through the analyzer, and then the chamber.
• Measuring the chamber air means that the air
is shuttled to the chamber first, then to the
analyzer.
General concepts
• If machines make you nervous, feel free to
watch this video of my introducing the
machine to a 7th grade class at
https://www.youtube.com/watch?v=tzzH6psMj5I
For measuring ambient air (analyzer first)
Path traveled BEFORE the analyzer
Path traveled AFTER the analyzer
Measuring chamber air (analyzer second)
Path traveled BEFORE the analyzer
Path traveled AFTER the analyzer
3/12/2009
CID
6
Path traveled BEFORE the analyzer
Path traveled AFTER the analyzer
Ambient
Chamber
3/12/2009
CID
7
Why does this matter?
• The IRGA tells you which measurement it is
actively taking, chamber or ambient air.
• Indicated by an asterisk on the data screen. If
near the CO2IN ppm, the machine is
measuring ambient air. If after the CO2OUT
ppm, has an asterisk, the chamber air is being
measured.
• You can actually hear the valves switching
every 30 seconds.
Let’s get started
• Make sure the black caps are not on the IRGA
before you power up!
Let’s get started
Programming the computer
1. Setting the file name.
– Hit start/enter. Enter a file name. hitting the 1 button
produces 1, hitting shift and then the number
produces A, hitting shift twice before pressing 1
produces letter B, three times will give C.
– Let’s use “GK12”
If this is a duplicate name, choose another file name. If
you end with a number, the computer will
automatically make your following entries the next
subsequent number.
--Hit enter.
Programming the computer
2. Time interval (in seconds).
Indicates how many seconds there are between
measurements.
Must use a value >0. I like 5 seconds.
--Hit 5, then enter.
Programming the computer
3.Setting Mode:
Default is P for Photosynthesis, so just hit enter.
Programming the computer
4. Control CS, AD, or LA?
Default is zero, so hit enter.
These stand for extra attachments you can add to
the IRGA such as a lamp.
Programming the computer
5. Leaf area? (cm )
This asks for the area of the leaf chamber. The area
is listed on the chamber itself. In this case it says
11cm^2, which is also the default.
Just hit enter.
Programming the computer
6. Flow rate? (lpm = liters per minute)
Default is 0.5, but the company recommends 0.3. so
type “.3” and hit return.
This controls the rate at which gas is pumped
through the chamber.
Programming the computer
7. Open or closed?
Asks if you want to use an open system, where
ambient air is compared to air in the chamber, or
closed, where the amount of CO2 in the chamber
is measured continuously.
Use open if using the leaf chamber
Use close if using the soil respiration chamber (not
included here).
Hit enter.
Taking measurements
Understanding data output
• The IRGA measures many things, for this
session you need only to observe:
– CO2 in and Out
– Where the asterisk is relative to the above 2
measurements
– Pn (photosynthetic rate)
Fun things to do with the IRGA
• Blow on the intake chamber. Have the
students see how high a CO2 concentration
they can get.
• Measure photosynthesis under different light
conditions.
• Water the plant after taking initial readings
– Get really fancy, have 2 identical plants. Water one
with cold water, and one with warm.