where will the plant get the CO2 it needs?

Some people grow a common houseplant called pothos completely underwater in their aquariums. I seem to recall there are some few other houseplants that are grown in aquariums.

Grizzman, I was hoping somebody here would know:)
Albert, thanks, I'll try a cutting from my pothos.

I'm not sure what my terrarium plant is, the label just said sedum. Now 11 days underwater, no sign of roots or rot.

There are certain plants that are aquatic and you can grow them completely submerged. I used to have a 40 gallon planted tank before I got married then got rid of it when I was moving out of my parent's house. You supply CO2 to the water through airline tubing running it through a diffuser. I used a "bubble ladder" which the CO2 bubble would zig-zag up a plastic ladder as it made its way up so it delayed it from escaping too fast. The longer you keep the bubble in the water the more it absorbs into the water. None of these plants were edible though, purely ornamental. You can check out www.plantedtank.net for more info.