New knowledge of how plants "breathe" may help us breed and select plants that would better survive scorching summers, says a University of Toronto study.

The paper, which offers the first example of a gene that controls how leaves close their surface pores, appears in the July 12 issue of Current Biology. "It's very exciting," says University of Toronto botany professor and senior author Malcolm Campbell. "This is a gene that helps regulate carbon dioxide uptake. If plants are the Earth's lungs, we've just discovered a key piece of information about how the Earth breathes."

The pores on the surface of plant leaves, called stomata, function like little mouths that open and close in response to cues such as light, temperature, and water availability. Using mouse-ear cress, a relative of mustard, cabbage and radish plants, Campbell and co-authors from University of Toronto and the University of Lancaster compared the cooling rates of plants with normal, high and low levels of gene activity. From their data, they were able to link the gene to plant exhalation.

The discovery is another step in understanding how plants respond to their environment. In hot temperatures, plants keep their mouths "shut" longer than usual, to avoid losing gases and water through evaporation. However, they must open their stomata at some point, both to pick up carbon dioxide needed for photosynthesis and to release oxygen back into the atmosphere. This new information will be important to plant breeders looking to improve crop resistance to drought, as well as to those seeking to understand plants' evolutionary responses to climate, says Campbell.

"These genes are of paramount importance. They allow plants to adapt to changes in light, carbon and water availability. Ultimately, they shape the flux of carbon and water throughout entire ecosystems and affect the carbon cycle on a global-scale." The study was supported by the University of Toronto, the Natural Sciences and Engineering Research Council of Canada and the Biotechnology and Biological Sciences Research Council of the U.K.