Indicator

[negativefx14]

I need a chemical indicator that will tell me when photorespiration occured, such as a chemical that will change colors when Phosphoglycolate or 3-phosphoglycerate comes about.

[MichaelXY]

Mr. Mistery suggested that you use Barium Hydroxide BaOH. Is this hard to come by?
I wonder if you could leave a vile of water in your test setup and use litmus paper to test the acid level changes of the water over time. I am sure Mr. Mistery will smack me for such a suggestion, so I am going to put on my anti mod helmet

[negativefx14]

I am not seeing how tha'd work...

Could you explain.

Im actually testing to see if photorespiration occured.

[MichaelXY]

Well I am assuming that you are looking for a change in CO2 levels. Since CO2 is an acid, you could take a neutral pH substance like H2O and monitor its acid level using litmus paper--which can be purchased easily. As for the water I would use distilled water. I think the CO2 would react with the water and give you an indication by reading pH. More CO2 more acid. Lower pH = more acid.
Ok maybe you should wait for better suggestions like from Mistery.

[negativefx14]

Sorry, but that doesnt really help me at all, thanks for the effort though.

It could be my answer, but im not seeing how CO2 does anything with Phosphoglycolate or 3-phosphoglycerate.

[mith]

Barium hydroxide is used for the titration(measurement) of weak acids, however the question here is for detection of photorespiration or how much oxygen is being used in a reaction with rubisco.

[negativefx14]

Ok, Ive figured it out. Since ammonia is a waste product of photorespiration, ill simply test for that, and if its presnt, photorespiration occured.

So I use nesslers reagent to test for ammonia.

But thank you guys very much for your help.

[mith]

only problem with this is you'll also need to identify the other routes that ammonia can go, does it get taken up metabolically? Does it degrade? Do other processes also contribute to ammonia concentrations?

[negativefx14]

This is true.

This lab design is killing me.

There are too many variables to controll with plants and too many to control with gases:(

[MrMistery]

sorry i misunderstood your experiment. I thought you were using different plants to test for intensity of photorespiration.
My best guess for doing this would be to take the same plant and place it media with increasing temperature. If it is a C3 plant(if it's C4 or CAM the experiment does not really make sense) when the temperature exceeds 25 degrees there will be a decrease in the intensity of photosynthesis(you can measure that by measuring the amount of CO2 as i said). This decrease in photosynthesis is actually an increase in photorespiration and can be plotted accordingly.
However, this is OK if you know what is causing it. Because the only conclusion you can draw from there is that photosynthesis decreases at high temperature. If you want to indicate clearly that photorespiration occured, then you will need to use a radioactive Oxigen isotope and track it through the cloroplast and peroxisome.
However, while the former can be easily done in any college lab, the latter needs ultrasecure conditions to make sure the scientist doesn't get cancer.

[negativefx14]

Thank you MrMistery, you've been a big help on both of my topics.