Farming has long focused on chemicals that can fight insects or kill weeds. Now scientists have discovered a molecule that could help crops deal with droughts, report findings appearing online this week in the Proceedings of the National Academy of Sciences.
Leaves are lined with tiny pores known as stomata that open and close to control the amount of water plants lose to the air through evaporation. During droughts, plants close stomata to limit water loss, but plants need carbon dioxide from the atmosphere to carry out photosynthesis and stay alive, so they need to open their stomata at least some of the time, leaving them vulnerable to dehydration.
A stress hormone called abscisic acid or ABA helps control the opening and closing of stomata, with plant cells producing increasing amounts of ABA as water levels fall to shut the pores down. Although spraying ABA on plants can improve how they respond to drought, it is too expensive for practical use in the field by farmers, leading researchers to hunt for cheaper ways to mimic it.
Plant cell biologist Sean Cutler at the University of California, Riverside, and his colleagues searched through many thousands of molecules to identify inexpensive synthetic chemicals that could imitate ABA. They discovered a molecule they named quinabactin that, in experiments with Arabidopsis, a plant used widely in biology labs, is nearly indistinguishable from ABA in its effects, activating the receptor molecules that ABA also binds with and triggering stomata closure, suppressing water loss and promoting drought tolerance. However, quinabactin is much simpler chemically than ABA and therefore easier to manufacture.
The success that Cutler and his colleagues saw with quinbactin might be surprising, given how quinbactin only activate three of the 13 receptors ABA targets in Arabidopsis — they initially thought they might need a molecule that activated more receptors to achieve the same effects. Similar results were seen with quinbactin on soybean, but not on corn. Future research that aims to help crops such as corn might look for synthetic chemicals that activate different or more receptors than quinbactin does. Toxicology and environmental impact studies will also be needed if companies hope to ever deploy such chemicals in the field.
As climate undergoes change globally and environments degrade worldwide, agricultural research will increasingly need to find ways for crops to deal with problems like too little water, Cutler said. “We’re not talking about making corn grow in the desert, but we hope we can maybe rescue 10 or 20 percent of crop yields under modest droughts,” Cutler said. The research team is now working with Syngenta Biotechnology to develop the technology.