New chemical could combat drought
Farmers in the U.S. witnessed record-breaking extremes in temperature and drought during the last two summers, which caused worldwide increases in the costs of food, feed, and fiber. Indeed, many climate scientists caution that extreme weather events resulting from climate change are the new normal for farmers in North America and elsewhere, requiring novel agricultural strategies to prevent crop losses. Now a research team led by Sean Cutler, a plant cell biologist at the University of California, Riverside, has found a new drought-protecting chemical that shows high potential for becoming a powerful tool for crop protection in the new world of extreme weather.
Named “quinabactin” by the researchers, the chemical mimics a naturally occurring stress hormone in plants that helps the plants cope with drought conditions.
Study results appear online this week in the Proceedings of the National Academy of Sciences. All land plants have intricate water-sensing and drought-response systems that are tuned to maximize their fitness in the environments they live in. For example, plants in environments with low water grow slowly so that they don't consume more water than is available.
“But since farmers have always desired fast-growing varieties, their most valued strains did not always originate from drought-tolerant progenitors,” explains Cutler, an associate professor of plant cell biology. “As a result, we have crops today that perform very well in years of plentiful water but poorly in years with little water. This dilemma has spawned an active hunt for both new drought-tolerant crops and chemicals that farmers might use for improving crop yield under adverse conditions.”
Working on Arabidopsis, a model plant used widely in plant biology labs, Cutler and his colleagues focused their efforts on tinkering with one of the plant's endogenous systems involved in drought responses. Plant leaves are lined with tiny pores, called stomata, which dynamically open and close to control the amount of water lost to the environment by evaporation. So that the plants can acquire carbon dioxide from the atmosphere, the pores need to be open some of the time, resulting in some loss of water.
During drought the stomata close firmly to limit water loss.
Behind the scenes, a small hormone called abscisic acid (ABA) orchestrates the opening and closing of the pores. Cells throughout the plant produce increasing amounts of ABA as water levels decrease. ABA then moves throughout the plant to signal the stressful conditions and close the stomata. Inside plant cells, ABA does its job by turning on a special class of proteins called receptors. The discovery in 2009 of ABA receptors by the same team behind the current breakthrough was heralded by Science magazine as one of the top breakthroughs of 2009 because of its relevance to the drought problem.
“If you can control the receptors the way ABA does, then you have a way to control water loss and drought-tolerance,” Cutler said. “It has been known for many years that simply spraying ABA on plants improves their water use and stress tolerance, but ABA itself is much too expensive for practical use in the field by farmers.”