High CO2 boosts plant respiration, potentially affecting climate and crops

Feb 09, 2009
Andrew Leakey and assistants at work in the Soy FACE facility at Illinois. Photo by Don Hamerman

The leaves of soybeans grown at the elevated carbon dioxide (CO2) levels predicted for the year 2050 respire more than those grown under current atmospheric conditions, researchers report, a finding that will help fine-tune climate models and could point to increased crop yields as CO2 levels rise.

The study, from researchers at the University of Illinois and the U.S. Dept. of Agriculture, appears this week in the Proceedings of the National Academy of Sciences.

Plants draw CO2 from the atmosphere and make sugars through the process of photosynthesis. But they also release some CO2 during respiration as they use the sugars to generate energy for self-maintenance and growth. How elevated CO2 affects plant respiration will therefore influence future food supplies and the extent to which plants can capture CO2 from the air and store it as carbon in their tissues.

While there is broad agreement that higher atmospheric CO2 levels stimulate photosynthesis in C3 plants, such as soybean, no such consensus exists on how rising CO2 levels will affect plant respiration.

"There's been a great deal of controversy about how plant respiration responds to elevated CO2," said U. of I. plant biology professor Andrew Leakey, who led the study. "Some summary studies suggest it will go down by 18 percent, some suggest it won't change, and some suggest it will increase as much as 11 percent."

Understanding how the respiratory pathway responds when plants are grown at elevated CO2 is key to reducing this uncertainty, Leakey said. His team used microarrays, a genomic tool that can detect changes in the activity of thousands of genes at a time, to learn which genes in the high CO2 plants were being switched on at higher or lower levels than those of the soybeans grown at current CO2 levels.

Rather than assessing plants grown in chambers in a greenhouse, as most studies have done, Leakey's team made use of the Soybean Free Air Concentration Enrichment (Soy FACE) facility at Illinois. This open-air research lab can expose a soybean field to a variety of atmospheric CO2 levels - without isolating the plants from other environmental influences, such as rainfall, sunlight and insects.

Some of the plants were exposed to atmospheric CO2 levels of 550 parts per million (ppm), the level predicted for the year 2050 if current trends continue. These were compared to plants grown at ambient CO2 levels (380 ppm).

The results were striking. At least 90 different genes coding the majority of enzymes in the cascade of chemical reactions that govern respiration were switched on (expressed) at higher levels in the soybeans grown at high CO2 levels. This explained how the plants were able to use the increased supply of sugars from stimulated photosynthesis under high CO2 conditions to produce energy, Leakey said. The rate of respiration increased 37 percent at the elevated CO2 levels.

The enhanced respiration is likely to support greater transport of sugars from leaves to other growing parts of the plant, including the seeds, Leakey said.

"The expression of over 600 genes was altered by elevated CO2 in total, which will help us to understand how the response is regulated and also hopefully produce crops that will perform better in the future," he said.

Source: University of Illinois at Urbana-Champaign

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Arkaleus
3 / 5 (9) Feb 09, 2009
This is not some radical new discovery in agriculture. Cannabis growers have used this technique for decades to maximize their yields. It's not that complicated - increased CO2 availability encourages higher rates of respiration in plants, increasing energy available to the plant.

The same process holds true for oxygen breathers, the richer the O2 environment, the greater levels of energy are available for use in the organism.
ryuuguu
4.6 / 5 (5) Feb 09, 2009
It is important research. Instead some hand waving and saying higher CO2 changes plant growth, they mesured which enzyme production is afected and by how much. These details are important if you want to understand what is happening in the plants.
dachpyarvile
3.3 / 5 (7) Feb 09, 2009
Yes, and increasing crop yields by ramped up respiration as high as 37 percent is a very good thing. It is not the gloom and doom predicted not too long ago by AGW advocates, wherein crop failures were anticipated. Quick! Look it up before their predictions disappear from the public view! :)

On the growing of cannabis, just moving the plants to the inside of your house does indeed raise CO2 levels with minimal effort. Some houses have ambient CO2 levels as high as 5,000 ppm inside. That is the level also regarded as the maximum safe level of exposure in enclosed spaces long-term. Many plants really like high CO2 levels. :)

Imagine food crops at CO2 levels of prehistoric times--on the order of 1000s ppm! More food; less starvation. Why would that be a bad thing?
SDMike
3.1 / 5 (11) Feb 09, 2009
Please don't tell Gore. Oh nevermind. He'll use this info to predict the return of the dinosaurs. We're all going to DIE!
MikeB
3.5 / 5 (8) Feb 09, 2009
If the temperature continues to moderate as it has with warmer nights and warmer winters, it seems that growing seasons will naturally become a little longer. Also, crops will thrive a little further north. With the improved growing seasons, larger growing areas and increased CO2 available for our crops, this appears to be good news.
gwargh
2.1 / 5 (9) Feb 10, 2009
At the same time, however, increased CO2 increases sugars only. I.e., plants grow, but they are high in sugars and low (by comparison) in proteins. A couple years ago I read studies on the slow decline of butterfly populations, because their larvae are not getting enough proteins and have to eat more.

What this basically means is that increased crop yields won't be such a great thing, since we'll need to eat more to get the same amount of nutrients.
Arikin
2.3 / 5 (6) Feb 10, 2009
Its not just about the amount of CO2. Temperatures will also increase. Which means that the types of plants suited to live in cooler temp zones will need to adapt or die out.

So I guess we should all change our diets to more tropical varieties :-)
Velanarris
4 / 5 (7) Feb 10, 2009
At the same time, however, increased CO2 increases sugars only. I.e., plants grow, but they are high in sugars and low (by comparison) in proteins. A couple years ago I read studies on the slow decline of butterfly populations, because their larvae are not getting enough proteins and have to eat more.

What this basically means is that increased crop yields won't be such a great thing, since we'll need to eat more to get the same amount of nutrients.

That is, unless you're an omnivore or carnivore and get the majority of your nutrients and protein from meat.
MikeB
3.4 / 5 (5) Feb 10, 2009
There is something seriously wrong with this article. It almost seems like it is saying that CO2 is good. We all know that the science is settled and CO2 is very, very bad. Articles like this only confuse the issue. Shame on you Physorg.
Fighting bad CO2 for the children,
Mike
dachpyarvile
3.7 / 5 (3) Feb 10, 2009
At the same time, however, increased CO2 increases sugars only. I.e., plants grow, but they are high in sugars and low (by comparison) in proteins. A couple years ago I read studies on the slow decline of butterfly populations, because their larvae are not getting enough proteins and have to eat more.

What this basically means is that increased crop yields won't be such a great thing, since we'll need to eat more to get the same amount of nutrients.


So, tell us how it was that butterfly populations survived and made it through the day when CO2 levels were in the 1000s ppm. They managed to survive to the present day. I'd also suggest looking for other reasons why butterflies are on the decline. It certainly is not due to CO2. We are nowhere near the levels of prehistoric times.
ontheinternets
2.4 / 5 (5) Feb 10, 2009
The politics of global warming too often stifles this kind of research (As an aside, I do to a large extent blame the Bush administration for lowering the level of discourse and necessitating a political opposition to its stated views.. but this is an aside). I applaud them for having the balls to carry on and risk getting blackballed by their contemporaries in the short term.
dachpyarvile
3.2 / 5 (5) Feb 10, 2009
Its not just about the amount of CO2. Temperatures will also increase. Which means that the types of plants suited to live in cooler temp zones will need to adapt or die out.

So I guess we should all change our diets to more tropical varieties :-)


I do not believe so. Frankly, that is an hypothesis that is not well-grounded in the science. Simply put, CO2 levels have been on the rise but global temps have fallen over the last three years. Remember, Winter 2008 recently was touted as "the coldest winter of the 21st century." And, this, in spite of increasing levels of CO2 ppm.

In addition, life usually adapts and moves with the changing of the climate, which change has been happening without the help of mankind for millions of years.
GrayMouser
3.3 / 5 (4) Feb 10, 2009
(As an aside, I do to a large extent blame the Bush administration for lowering the level of discourse and necessitating a political opposition to its stated views.. but this is an aside).

Bush is no different that AlGo stomping on scientists while he was VP. With the exception that nothing was done to Hansen (when he could have been legally fired) and others were forced out.
Velanarris
4.2 / 5 (5) Feb 10, 2009
(As an aside, I do to a large extent blame the Bush administration for lowering the level of discourse and necessitating a political opposition to its stated views.. but this is an aside).

Bush is no different that AlGo stomping on scientists while he was VP. With the exception that nothing was done to Hansen (when he could have been legally fired) and others were forced out.
Yeah but if you fire Hansen he'd just use it to further his agenda and spread the misinformation that he was "silenced" by the administration.
holmstar
1 / 5 (5) Feb 10, 2009
This study simply assumes a higher level of CO2 and all else remaining constant. That is NOT very likely to be the case if *global* levels of C02 were to rise significantly.
tkjtkj
2.7 / 5 (3) Feb 10, 2009
Such an expensive experiment! And done with no attention to measurement of oxygen generation???

what's going on here!!!!

Velanarris
4.2 / 5 (5) Feb 10, 2009
This study simply assumes a higher level of CO2 and all else remaining constant. That is NOT very likely to be the case if *global* levels of C02 were to rise significantly.
Reasoning for this hypothesis is?
gwargh
1.3 / 5 (3) Feb 11, 2009
At the same time, however, increased CO2 increases sugars only. I.e., plants grow, but they are high in sugars and low (by comparison) in proteins. A couple years ago I read studies on the slow decline of butterfly populations, because their larvae are not getting enough proteins and have to eat more.

What this basically means is that increased crop yields won't be such a great thing, since we'll need to eat more to get the same amount of nutrients.

That is, unless you're an omnivore or carnivore and get the majority of your nutrients and protein from meat.


And that meat at some point got a part of its proteins from plants as well as cellular processes. The point I'm trying to make is that there's two sides to every coin, and you cannot state explicitly that an increase in CO2 is a good thing. It's not all bad, but it's not all good either.

So, tell us how it was that butterfly populations survived and made it through the day when CO2 levels were in the 1000s ppm. They managed to survive to the present day. I'd also suggest looking for other reasons why butterflies are on the decline. It certainly is not due to CO2. We are nowhere near the levels of prehistoric times.


Perhaps because plants had more time to adapt to higher CO2 levels, and so did butterflies. I am not prophesying the extinction of butterflies, I'm merely saying there's a pressure that is causing a decrease in their populations, and it could be increased sugar production.

The butterflies of today are not the butterflies of prehistoric times and neither are the plants. Both have adapted to change, and I expect they will do so again, though change takes time.
dachpyarvile
5 / 5 (2) Feb 11, 2009
And that meat at some point got a part of its proteins from plants as well as cellular processes. The point I'm trying to make is that there's two sides to every coin, and you cannot state explicitly that an increase in CO2 is a good thing. It's not all bad, but it's not all good either.


CO2 is CO2. Increases will indeed be a good thing. Life will adapt or die. The evidence of the past shows that most life will adapt to changes in levels of CO2.

Perhaps because plants had more time to adapt to higher CO2 levels, and so did butterflies. I am not prophesying the extinction of butterflies, I'm merely saying there's a pressure that is causing a decrease in their populations, and it could be increased sugar production.

The butterflies of today are not the butterflies of prehistoric times and neither are the plants. Both have adapted to change, and I expect they will do so again, though change takes time.


Butterflies sip nectar. Nectar contains high amounts of various sugars and also some amino acids. The plants did not have to adapt to high CO2 levels because the CO2 levels already were high when plants emerged onto land in the beginning. If anything, they had to adapt to having *less* CO2 available.
gwargh
1 / 5 (4) Feb 12, 2009
Point taken, however we are discussing butterfly larvae, which do not in any way sip nectar. They eat leaves and shoots, both of which are usually not at all high in sugar and far higher in protein. And plants have now (I think you'll agree) adapted to less CO2 in the environment. So until they readapt, there will be certain repercussions.

And no, CO2 increases are not necesarily a good thing. Yes, life wil adapt, but as humans our concern is humanity and its survival. And so our concern is to figure out HOW to adapt, and how to thrive, not to state that everything will be better now and ignoring any problems that might arise.
Velanarris
5 / 5 (5) Feb 12, 2009
Yes, life wil adapt, but as humans our concern is humanity and its survival.
That may be my concern, and probably the concern of most people, however, looking at the sensationalist journalism about the issue it appears people are more interested in trying to force climate to adapt to us by remaining in a steady state of sorts.
gwargh
1 / 5 (3) Feb 13, 2009
Agreed, however, the same is true of those fighting against sensationalism. If we are to portray truth (or as much truth as we can portray) and not merely one side of the issue, "High CO2 boosts agriculture" sounds quite sensationalist as well.
I am merely appealing for a level-headed approach. Then again, not everyone is able to understand that.
Velanarris
5 / 5 (4) Feb 13, 2009
"High CO2 boosts agriculture" sounds quite sensationalist as well.

Well I'd ask you, how so?

High CO2 does boost agriculture, it's a factual, known element.
Now when you see a headline like "Global warming threatens artic sea life" but the abstract, as well as the original research fail to use any known elements or definitive statements to support the title, that is sensationalism.

I do agree that there are sensationalists on both sides of the argument, and if we're to let science do it's work a more level headed approach is necessary, on both sides.
dachpyarvile
5 / 5 (1) Feb 17, 2009
Point taken, however we are discussing butterfly larvae, which do not in any way sip nectar. They eat leaves and shoots, both of which are usually not at all high in sugar and far higher in protein. And plants have now (I think you'll agree) adapted to less CO2 in the environment. So until they readapt, there will be certain repercussions.


Apparently, you did not read the article--at least not the part about the genes that switched on when the levels of CO2 were raised. That is exactly what "adapting" is all about. Genes switch on. Genes are modified over time. Fact is, these particular plants had the genes all along. Most others do as well. The larvae seem to be doing just fine. In addition, protein synthesis depends on CO2 and amino acids that are based on hydrocarbons. Those that form and are based on metallics/non-metallics in minerals depend on what is in the soil, not the levels of CO2 in the atmosphere. More and more of our soils are depleted of certain minerals and certainly produce less of the amino acids needed for protein synthesis. But, that is caused by mineral depletion, not increases in ppm of CO2. We too often throw out the dead leaves that are dropped by the trees. By interrupting the life cycle in this way, we deprive the trees of the very elements they need to thrive and produce what is needed by the larvae. The minerals lost from the ground must be replaced somehow if we continue to leech minerals out of the soils in which trees grow. No changes in CO2 levels will improve or worsen this situation.

And no, CO2 increases are not necesarily a good thing. Yes, life wil adapt, but as humans our concern is humanity and its survival. And so our concern is to figure out HOW to adapt, and how to thrive, not to state that everything will be better now and ignoring any problems that might arise.


CO2 increases on the order of what we are seeing will be a good thing and are a good thing. Were you aware that the African Savanna has been increasing and that the Sahara has slowed its growth, looking like it is going to turn back and shrink? That certainly will be a good thing for the peoples who live there, as well as the wildlife.

Humans will have no problem adapting to rising CO2 levels. We do not have to figure out anything in that area. Talk to me about how humans will need to adapt when CO2 levels have risen to 15,000 ppm. That will never happen. So long as photosynthesis has been happening, the CO2 levels have never been that high in that part of the history of the world. The highest levels of which I am aware were during the Permian, iirc, and were at just over 7,000 ppm. Life did just fine until the Permian extinction. Humans can handle well over 5,000 ppm of CO2 in open air. 5,000 ppm is regarded as the OSHA safe long-term limit in enclosed areas.
dachpyarvile
5 / 5 (2) Feb 19, 2009
At the same time, however, increased CO2 increases sugars only. I.e., plants grow, but they are high in sugars and low (by comparison) in proteins. A couple years ago I read studies on the slow decline of butterfly populations, because their larvae are not getting enough proteins and have to eat more.

What this basically means is that increased crop yields won't be such a great thing, since we'll need to eat more to get the same amount of nutrients.


One other thing: Your above comment is not true. Plants are growing larger in the wake of rising levels of CO2. This has just been confirmed by observation of trees, which are growing larger and sinking more carbon in their tissues. In point of fact, an article here on Physorg.com discusses this fact.

Plants do not build their superstructure on sugars. They build their superstructures in their tissues by increasing cellulose and protein production. Thus, in order to grow larger the plants must be producing more cellulose and proteins in order for there to be more tissues as they grow larger. Take some botany courses in a reputable and accredited school and you will learn a bit more about this.
Velanarris
5 / 5 (2) Feb 19, 2009
Thus, in order to grow larger the plants must be producing more cellulose and proteins in order for there to be more tissues as they grow larger. Take some botany courses in a reputable and accredited school and you will learn a bit more about this.


Dach, wouldn't the sugars generated be necessary to fuel the processes that allow increased cellulose and protein? I'm not big on botany but in order for animals to grow they could receive all the protein in the world but if they aren't receiving the sugars to burn that protein is mostly wasted, or processed in it's stead rather than used to form structures in the body.
dachpyarvile
5 / 5 (1) Feb 20, 2009
Thus, in order to grow larger the plants must be producing more cellulose and proteins in order for there to be more tissues as they grow larger. Take some botany courses in a reputable and accredited school and you will learn a bit more about this.


Dach, wouldn't the sugars generated be necessary to fuel the processes that allow increased cellulose and protein? I'm not big on botany but in order for animals to grow they could receive all the protein in the world but if they aren't receiving the sugars to burn that protein is mostly wasted, or processed in it's stead rather than used to form structures in the body.


Absolutely in animals they must process glucose to run certain of the processes. However, many of the amino acids must be obtained from plants. Animal tissues manufacture very few of the amino acids needed. However, they most certainly need glucose to fuel the ATP cycle as well as other chemicals.

Plants, on the other hand, manufacture their amino acids from the sugars they previously produced via photosynthesis. These are then converted to proteins in the plants, which become part of the superstructure of the cells in the plants. These proteins are regularly broken down into amino acids and recycled into proteins again to be placed into the superstructures of the cells of the plants. More sugars available mean more raw materials for processing into amino acids and later into proteins.

Excess sugars are stored in the fruits of the plants along with the amino acids and proteins that form part of the superstructure of the fruits/seeds. The highest levels of amino acids are found in the reproductive organs of the plants anyway. This has always been so as far as is known.
Velanarris
5 / 5 (2) Feb 20, 2009
So by your process train above, the presence of more CO2 alone can lead to enhanced growth given that the soil or other medium of the plant is nutrient rich.
dachpyarvile
5 / 5 (1) Feb 20, 2009
Absolutely. Consider prehistoric times. Animals grew to enormous sizes and such growth can only occur when food and nutrients are plentiful. Dwarfism among animals such as that which occurred with Dwarf Mammoths and so forth was a result of lessened available nutrition. In addition, when plant respiration increases during daylight hours, more oxygen is produced as a by-product of photosynthesis.

Latest data suggests that insects also grow larger when oxygen is more plentiful in the atmosphere. This certainly would go toward explaining dragonflies with two-foot wingspans. Increased levels of CO2 also cause increased growth in plants, which would go toward explaining very large plants in prehistoric times when CO2 levels were much higher than they are today. Things do not grow as much or thrive when nutrient levels are low. That is a fact of nature that is observable and has been observed for many years.

Most plants also like it warmer. So, we could be looking at an increase of atmospheric oxygen as a potential corollary to increased CO2 levels, too. Thing of it is, many kinds of plants can continue to grow and do so more rapidly with CO2 levels up to 0.9% of the atmosphere. After that the plants begin having difficulties. This is a scientific fact and has been observed in botanical study. Even General Botany books also state the same thing. Our current levels of CO2 only make up around between 0.03% and 0.04% of the atmosphere. We have a long way to go before getting to such high levels as that given above that interfere with the normal processes in plant biology.