I was doing research for a college assignment over the weekend about Photorespiration and I lean’t something. Its turns out that high carbon dioxide concentration in the atmosphere is not so bad because it prevents Photorespiration.

Photorespiration is a process that occurs at low carbon dioxide concentration and high oxygen concentration where C3 Plants react with ribulose bisphosphate to form 3-phosphoglycerate and 2-phosphoglycolate. The reaction is illustrated below;

In normal Photosynthesis, ribulose-bisphosphate (RUBP) reacts with carbon dioxide (CO₂) to form 2 molecules of 3-phosphoglycerate (3PGA) like this;

( RUBISCO is an enzyme that speeds up the reactions)

When the RUBP reacts with oxygen, plants must convert the phosphoglycolate to 3PGA which would have been formed if RUBP had reacted with CO₂.

So to do this, it goes through a series of reactions which include conversion to glycolic acid then to glycine, serine (glycine and serine are both amino acids ) and finally to 3PGA.
But all this consumes energy that would be used for other processes. So its a wasteful process.

If Carbon dioxide Concentrations were high, the phosphoglycolate wouldn’t be formed so there would be no waste. And since the energy comes from breakdown of food stored in the plant, there is a net loss in total food a plant would produce when phosphoglycolate is formed. Most important crops photorespire about half of their potential yield away.

So if carbon dioxide concentrations were high, the net loss of food by the plant would be reduced and so plants would give high yields. Problems like famine would be reduced and a whole range of other things.

Just want to point out that high carbon dioxide concentration causes GLOBAL WARMING so its bad.

But it also improves crop yields, so on the other hand its good. So basically high carbon concentration is good and bad.

So when measures are being taken to reduce carbon concentrations, both the good and bad sides should be considered so as to benefit both plants and the environment. Because both of them are essential to our livelihood.

Read More about Photorespiration at;
http://www.steve.gb.com/science/photorespiration.html
http://www2.mcdaniel.edu/Biology/botf99/photodark/photorespiration.htm
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/C4plants.html
http://www.marietta.edu/~spilatrs/biol103/photolab/photresp.html
http://en.wikipedia.org/wiki/Photorespiration