The discovery of this signaling mechanism, a kind of biological Morse code used by plants to control the opening and closing of stomata, is described in the June 28 issue of Nature by biologists at the University of California, San Diego working with two German collaborators. Their achievement opens up a new area of study for plant scientists and may one day allow them to engineer drought-resistant crops that can more effectively survive water shortages by limiting water loss during droughts.
"Much of the land used for agriculture is not irrigated because water is either unavailable or too expensive," says Julian I. Schroeder, a professor of biology at UCSD who headed the research team. "So if crops can be engineered to respond to droughts by more rapidly and effectively closing their stomatal pores, where 95 percent of the water loss in plants occur, they could better survive drought periods by conserving water until the next rain hits. The commercial impact would be substantial. In the past decade, the average loss in the corn crop in the United States during three major droughts was 30 percent."
In their study, the scientists discovered that specialized cells in the leaves called guard cells that surround each pore, or stoma, "tune in" to the frequency of calcium
oscillations in the cell, just as we might tune into a specific radio signal on the FM dial. When these oscillations of calcium concentrations in the cell are at just the right frequency, the scientists discovered, the guard cells respond by closing the stomata for extended periods. When the oscillations are not at the right frequency, the stomatawhich initially close in response to elevations in calciumreopen within an hour.