In response to drought, sunlight, and other stimuli, guard cells control the opening and closing of microscopic stomatal pores on leaves of plants through which the plant gives off water vapor and oxygen to the atmosphere and takes in carbon dioxide for photosynthesis. Guard cells thereby moderate the amount of water and carbon dioxide in the plants. Researchers Sarah M. Assmann, professor of biology at Penn State, and Xi-Qing Wang, a postdoctoral scholar at Penn State, along with collaborators at the University of North Carolina, discovered that by altering a specific protein in the guard cells those cells had less control over the amount of water lost by the plants through their stomatal pores. The research team's results will be published in the 15 June 2001 edition of Science.
"The potential agricultural significance is being able to regulate stomatal apertures," Assmann says. "From a farmer's perspective, finding a way to maximize photosynthesis and yield, and a way to minimize irrigation, which can be expensive, would be important."
In Arabidopsis thaliana, the researchers' model organism, also known as mouse-ear cress, the natural hormone abscisic acid (ABA) usually promotes water conservation under drought conditions by signaling guard cells to change their volume, thereby decreasing the size of the stomatal pores and limiting the amount of water lost by plants. The North Carolina researchers identified Arabidopsis plants in which a naturally occurring G-protein component within the guard cells, the G-protein alpha subunit, had been eliminated. The Penn State group analyze
Contact: Steve Sampsell