Plant Carbon Dioxide Measurement
I'm doing a science project and I was going to do it on on much
carbon dioxide a plant makes.
What type of plant should I use? Will I be able to find a co2 gauge that
is small enough?
NOTE: Dr. Ross' response is based on the assumption that you wanted
to measure oxygen release rather than carbon dioxide. Measuring
oxygen does make much more sense in trying to measure photosynthetic
This is a fairly long answer, but it mainly will tell you web sites to
look at, maybe with help from your teacher. As you think about the
answers people give you, you might want to ask other questions. You
might be asking this question because you want to know about global
- Show quoted text -
climate change, or about crops and food, or even how long people can
live in a space station, if they have plants too. But we'll try to
answer your question as it was asked.
You could watch a plant called/ Elodea/, an aquatic plant, take CO2 out
of the water (bicarbonate in solution), which you don't "see" by
watching it produce O2 (gas) bubbles that you DO see. Do it with and
without a bright light on the plant.
OR, some school demos measure photosynthesis indirectly, by masking part
of a leaf so it doesn't get light (chlorophyll disappears in that part),
and measuring starch produced (or not produced, if it's under the foil
*here are some web sites on photosynthesis*
cute little Flash from Nova / PBS
Simplified version from the Public TV Show, Newton's apple- "
The "Teachers Guide" has an "Activity" that could be used to develop an
Experiment- leaves from different species, OR foil left on for different
amounts of time, OR foil masks on plants growing at different light
levels (or plants growing in different environmental conditions in
general, as long as the light/water/nutrients/toxins were not so
limiting/toxic as to kill the plant).
Cartoonish but accurate from "Flying Turtle"
There is a PBS show, "Middle School Biology- Exploring Photosynthesis".
It's scheduled on August 30th (in Iowa) :
"It reveals the chemical
processes of both respiration and photosynthesis and the products that
are produced. An experiment with a variegated leaf demonstrates that
photosynthesis takes place in the green cells of leaves. " I don't know
when or if it will be scheduled on other PBS stations.
_http://photoscience.la.asu.edu/photosyn/study.html_ (Long, text-filled;
has a section, "Why study photosynthesis?")
cool way to measure O2 evolution in leaf disks, by time-to-float. Very
British (sodium hydrogen carbonate is sodium bicarbonate, aka baking
soda, if you're at home); go down the page to "*STUDENT ACTIVITY GUIDE*"
for explanation and pictures before reading the rest! It's designed as a
species comparison (shade tolerant species vs high-light requiring
species, and white light vs. green light, but could be adapted to
compare plants grown in different conditions, or providing different
amounts of light to the disks in the syringes.
Elodea/ experiment. Uses pH of solutions to determine differences in CO2
depletion. Variable is light intensity- she might think of others, but
it is a short-term experiment)
Another/ Elodea/ experiment -
counts O2 bubbles
(1-/ Elodea/ photosynthesis and respiration, uses pH meter, could
substitute pH paper; 2-pigment separation, no solvent specified)
_http://www.science-projects.com/PhotosynthPigments.htm_ This has some
really cool ideas, but some uncommon (and some nasty) chemicals; does
indicate some ways to simplify. One could choose one of the methods,
and, if it works well at home/school, use it to explore various
questions about plant pigments in relation to photosynthesis or species
more pigment separation-
and only uses rubbing alcohol, not lighter fluid!
by starch production. Impacts of light/dark and of CO2 concentration in
air (CO2 in air of one flask removed by absorption in potassium
hydroxide solution.) Very cool website, mouse-over at bottom. Also
British: / Industrial Methylated Spirit/ is denatured ethanol. Not sure
why the caution about not using pure ethanol. Maybe it's too flammable.
To extract chlorophyll (and measure it by spectrophotometry) we use cold
80% ethanol (in H20), but it takes 2 days in the dark to get it out. Hot
(or warm) is faster. Quite possible that rubbing alcohol (70%
isopropanol, I think) would work.
("Starch pictures"- advanced version of above. Could make the "picture"
in reverse, by masking part of the leaf, and putting it in high light
for the experiment. Sounds a little tricky/messy for setting up at home;
requires hot alcohol and iodine. Lugol's solution (???) in supplies list
never used in procedure.)
Your teacher needs to give you some help on your project because you
have a basic problem:
Plants consume CO2. In general they do not make CO2.
Even when you resolve that understanding, actually measuring the level
of CO2 in the enclosed container you will have to use could be tricky.
Search the web for sites similar to what you propose to do and see how
other people in the past have dealt with, for the objective of your project.
Cellular respiration functioning in plants is dwarfed by animals, so
carbon dioxide production is minimal at best. Photosynthesis would
tend to use up any CO2 produced so measuring any release into the
environment will be next to nothing, except maybe a very small amount
at night with some plants. As a former junior high teacher, I can not
recommend this project.
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Update: June 2012