Can we genetically modify plants to absorb more CO2?

Chris Smith put this to fellow Naked Scientist, Kat Arney...

Chris - Kat, here is one for you from (Toya) who says, "Can we genetically modify plants in order to absorb more CO2?" I presume they're going for the point that we're worried about CO2 levels in the atmosphere.

Kat - Yeah, kind of plant-based carbon scrubbing. I think in theory and it's important to think about how the plants use CO2. So you use carbon dioxide in a process called photosynthesis which is basically sticking together carbon dioxide and water to make sugars. It's kind of the reverse of what we do when we make energy by eating sugar and turning into carbon dioxide and water. So, they do this through a whole series of enzymes. These are kind of chemical catalysts that do all these different processes, that take the carbon dioxide, that take the water, they kind of stick it together, use the energy from light to do that kind of chemical reaction. So in theory, I think that you could probably make some tweaks to those enzymes to make them more efficient, make them run in slightly different ways. I also think that there are other things that would probably speed up that reaction - things like heat tends to speed up biological processes to a certain point. After that point, you tend to damage the enzymes. So I think if you could make those enzymes in some way, run more efficiently at the temperatures that plants normally grow at, or put the entire world in a greenhouse which we're kind of doing, that might work.

Chris - Thank you very much, Kat.