To simulate an insect attack, the scientists painted a solution of jasmonic acid, a chemical messenger that plants produce in response to various types of stress, onto the leaves of poplar trees in a closed chamber. They then administered carbon dioxide gas "labeled" with radioactive carbon-11 to individual leaves, where it is quickly converted to sugar, and traced the movement of this radiolabeled sugar through the plants using autoradiography and other techniques. Autoradiography allows for taking a snapshot in time showing the precise location of the radiotracer within the plant. With this and other techniques, the scientists can compare what that plant does with the carbon dioxide both before and after an attack.
"Carbon dioxide is a plant's major resource. To see how it is allocated into various biochemical pathways is an incredibly powerful tool for learning how plants cope with stress," says plant scientist Michael Thorpe who is helping to build the plant-imaging program at Brookhaven.
Plants subjected to the jasmonic acid "attack" produced more radiolabeled sugar and delivered more of it to the roots than plants untreated with the hormone. "This is pretty convincing evidence that plants can respond 'passively' by redirecting their nutrients away from the site of attack and placing them into storage for later regrowth," Ferrieri said.
Supporting evidence comes from the amount of carbon-11 the scientists detected in isoprene, a hydrocarbon gas that is a byproduct of sugar synthesis in the leaves. That research, reported in Plant, Cell & Environment, shows that, in response to jasmonic acid "attack," the plants diverted more newly acquired carbon into isoprene production. "Scientists are only just beginning to realize that isoprene has a vital role as an antioxidant in helping plants tolerate ma
Contact: Karen McNulty Walsh
DOE/Brookhaven National Laboratory