how to measure CO2 uptake in plants

[SW]

hello. i am a high school student and i am doing a project on carbon dioxide and ways to remove carbon dioxide becuase of the greenhouse effect and increased carbon dioxide in the atmosphere. i wanted to compare different plants an find out whihc plants remove more carbon dioxide beucase it would be more beneficial to have plantsthat remove more carbon dixide. but before i could test the plants, i thought that i needed to know ways to measure carbon dioxide uptake in plants. How would i measure the rate of comsumption of CO2 in plants?

[deleted-2131]

Are you looking to see if plants absorb CO2 from the air? Is so, you will find it difficult because plants use O2 and give off CO2. In general, plants are CO2 producers and animals are CO2 consumers.

If you could give a few more details on what exactly you are hoping to accomplish with plants, I will be able to give a more helpful reply.

[deleted-71447]

SW,
It would be helpful to keep all of your questions in the same topic (use "post reply" to follow up on a question instead of using "post new topic"), because it will allow people to skim the background of your project and what has already been discussed.

If you do a google search for "carbon fixation rates" you will find a variety of articles and discussions that will help you figure out how you can estimate the rate of CO2 update by plants. For example, this page might give you an idea of a very simple (though maybe too simplistic) method that could be used.
http://fins.actwin.com/aquatic-plants/m ... 00269.html

[SW]

for my science project, measuring carbon dioxide uptake by various plants, i have researched for ways to measure carbon dioxide. There were three methods that i've found. It was through titration, chromotography, and the bowen- ratio method. i think that the chromotography would work the best. i was wondering if there were other suggestions of possible ways to measure carbon dioxide uptake in plants, or if you also think chromotography method is reasonable.

[deleted-71447]

Good work on finding possible methods. A gas chromatograph (GC) is certainly a suitable tool to measure CO2 concentrations in gas samples, but this is not a cheap or simple instrument. Do you have access to a GC? Do you plan to team up with a researcher at a local university?

Infrared gas analyzers are also used in CO2 uptake experiments. For solid plant samples, researchers often use an "elemental analyzer", which is another expensive piece of equipment.

If you can find researchers to assist you with these "high-end" techniques, that is great. If not, it is possible to use a very simple and cheap approach to estimate the carbon uptake. For example, take a look at table 5.4 on this page:
http://www.icsu-scope.org/downloadpubs/ ... ter05.html
The total carbon integrated into a growing plant can be estimated from the dry weight of the plant and its roots. These types of estimates will be sufficiently accurate if the differences in growth rate (and carbon uptake) are large.

If you work with terrestrial plants, you might also consider the effects on the carbon budget of plant root exudates and microbial communities associated with the roots. For example, you could design an experiment with (1) plants in potted soils, and (2) identically treated potted soils without plants. Comparing the changes in soil carbon mass in groups (1) and (2) might provide some interesting results. Soil carbon content values of soil can be estimated using an elemental analyzer, or simply by burning the soil in a laboratory furnace and then converting the volatile solid content to a carbon value:
http://compost.css.cornell.edu/calc/carbon.html