MadSci Network: Botany

Re: Can plants grow at gretaer than atmospheric air pressure

Date: Mon Feb 2 17:18:09 2004
Posted By: David Hershey, Faculty, Botany, NA
Area of science: Botany
ID: 1075527828.Bt

Growing plants at above normal atmospheric pressure would involve a hyperbaric 
chamber. One recent study on ginkgo found as much as a 250% increase in the 
photosynthesis rate when the carbon dioxide was increased 500% and atmospheric 
pressure was increased 25%. I contacted the lead author, Sara Decherd, and she 
kindly told me that they found no significant effect on photosynthesis with a 
25% increase in atmospheric pressure alone. She was also not aware of much 
other research on plant growth in hyperbaric chambers. It seems to be an area 
that has not been thoroughly studied. The ginkgo research was recently 
featured in a news release, "A Lot of Hot Air: How the Dinosaurs Grew So 

NASA has done work on growing plants at less than atmospheric pressure in 
hypobaric chambers. Hypobaric greenhouses with one-sixteenth the pressure of 
an Earth atmosphere may be required for Mars colonization. 

At normal atmospheric pressures, increasing the carbon dioxide concentration 
up to about 1,000 ppm often increases plant growth. Current atmospheric carbon 
dioxide is about 360 ppm. Thus, you might expect a positive effect on plant 
growth in a hyperbaric chamber. I doubt a soda bottle would be a satisfactory 
hypobaric chamber. It would be difficult and expensive for a school student to 
maintain an elevated carbon dioxide level in a hyperbaric plant growth chamber 
because a plant can rapidly deplete the carbon dioxide given its low 
concentration and the limited chamber volume. Be very cautious if you try to 
make your own hyperbaric chamber because an explosion is always a possibility.

It would be much easier to demonstrate effects of carbon dioxide enrichment at 
normal atmospheric pressures. A soda bottle system to inexpensively induce 
carbon dioxide deficiency in plants can be built using rubber stoppers, 
aquarium tubing, aquarium valves and an aquarium air pump (Hershey 1992, 
1995). The same system could be used to elevate the carbon dioxide level using 
dry ice or acid mixing with calcium carbonate as a source of carbon dioxide.



A Lot of Hot Air: How the Dinosaurs Grew So Monstrous

NASA Greening Mars

Hershey, D.R. 1995. Plant Biology Science Projects. New York: Wiley.

Hershey, D.R. 1992. Plants Can't Do Without CO2. Science Teacher. 59(3): 41-43 

Effect of Carbon Dioxide Enrichment and Light

Crop ecology: Carbon dioxide

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