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 CO 2 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 7 th grade class at

For measuring ambient air (analyzer first) Path traveled BEFORE the analyzer Path traveled AFTER the analyzer

3/12/2009CID6 Measuring chamber air (analyzer second) Path traveled BEFORE the analyzer Path traveled AFTER the analyzer

3/12/2009CID7 Ambient Chamber Path traveled BEFORE the analyzer Path traveled AFTER the analyzer

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.