While this protective mechanism minimizes the damage to plants, he adds, it also minimizes their ability to photosynthesize when ozone levels are high, because the stomatal pores are also the breathing holes in leaves through which carbon dioxide enters leaves. The result is diminished plant growth or at least less than one might expect given the rising levels of carbon dioxide.
Some scientists assessing the impacts of rising greenhouse gases had initially estimated that increased plant growth generated from extra carbon dioxide in the atmosphere could sequester much of the excess atmospheric carbon in plant material. But in a paper published last July in Nature, researchers from Britains Hadley Centre for Climate Prediction and Research concluded that the damage done to plants by increasing ozone pollution would actually reduce the ability of plants to soak up carbon from the atmosphere by 15 percent which corresponds to about 30 billion tons of carbon per year on a global scale---a dire prediction given that humans are already putting more carbon into the atmosphere than plants can soak up.
The discovery of the ozone-responsive plant gene was made when Jaakko Kangasjarvi and his collaborators at the University of Helsinki in Finland found a mutant form of the common mustard plant, Arabidopsis, that was extremely sensitive to ozone. They next found that this mutant does not close its stomatal pores in response to ozone stress.
When the mutant plant is exposed to ozone, the leaves lose their dark green color and eventually become white, said Kangasjarvi, who is also one of the principal authors of the study. This is because the stomatal pores in the leaves stay open even in the presence of high ozone and are unable to protect the plant.
The scientists found th
|Contact: Kim McDonald|
University of California - San Diego