Fresh water, a critical resource for life on Earth, soon may become dangerously scarce. Water use has been growing at more than twice the rate of population increase in the last century, and by 2025, the demand for fresh water will exceed available resources for two-thirds of the world population, according to the United Nations.
Now, thanks in part to a $1.5 million collaborative grant from the National Science Foundation, researchers at UGA, the University of California at Riverside, the University of Texas and the University of Buffalo are looking to Mother Nature for clues about how plants survive in water-limited environments and what people can do to engineer crops that require less of this precious commodity.
“Agaves, yuccas and their relatives, together with orchids living in the canopies of tropical dry forests, are known for their ability to thrive in water-limited environments,” said Jim Leebens-Mack, an associate professor of plant biology in UGA’s Franklin College of Arts and Sciences and principal investigator for the project. “If we can understand how these plants adapt to water stress at the molecular level, we can learn how to increase water efficiency in economically important plants like biofuel and food crops.”
During normal photosynthesis, most plants absorb carbon dioxide from the atmosphere through pore-like structures on leaves known as stomata. The CO2 combines with water and sunlight to produce the carbohydrates a plant needs to grow as well as oxygen.
The same pores that absorb CO2 also allow water to escape through evaporation. That’s not a problem for plants that receive plenty of rainfall or help from irrigation, but it could be fatal for vegetation growing in dry climates.
Using a unique process known as crassulacean acid metabolism, or CAM photosynthesis, orchids and agave close these pores during the daytime when rising temperatures cause the most evaporative water loss. In CAM species, the pores open and take in CO2 during the cooler evening and the carbon is stored for photosynthesis of carbohydrates when the sun is out during the day.
“It’s as if a plant is deeply inhaling CO2 at night and doing photosynthesis while holding its breath during the part of the day when it is in greatest danger of losing valuable water,” Leebens-Mack said. “If we get a firm grasp of the genetics involved in this process, we may be able to transfer it to biofuel and feed crops that are sensitive to water shortages.”