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Surprising study results give reason for optimism in searching for greater environmental sustainability and developing plantation-scale biomass sources that can serve as fossil fuel alternatives. 32 April 2020 Inhalation Back Page Poplar trees genetically modified not to damage air quality grow as well as non-modified trees Surprising results toward greater environmental sustainability and fossil fuel alternatives Science Daily has reported that "while providing benefits to the environment, some trees also emit gases to the atmosphere that worsen air pollution and alter climate. Field trials in Oregon and Arizona show that poplar trees, which emit trace amounts of the gas isoprene, can be genetically modified not to harm air quality while leaving their growth potential unchanged." e finding were published in Pro- ceedings of the National Academy of Sciences by a team of scientists from e University of Arizona; the Institute of Biochemical Plant Pathology at Helmholtz Research Center Munich, Germany; Port- land State University and Oregon State University. Scientists from the University of California, Riv- erside, NASA's Goddard Space Flight Center and the Institute for Microbiology in Greifswald, Ger- many also supported the study. Poplar trees grow quickly and are a source of biofuel and other prod- ucts including paper, pallets, ply- wood and furniture frames. Over the past 15 years, poplar planta- tions have more than doubled and now cover 9.4 million hectares (36,294 square miles) globally. Isoprene contributes to global warming In response to climate stress- ors such as high temperature and drought, poplars and other trees produce isoprene in their leaves, which signals cellular processes to produce protective molecules, ex- plained Science Daily. However, isoprene is volatile and millions of metric tons leak into the at- mosphere each year. In turn, the emitted isoprene reacts with gases produced by tailpipe pollution to produce ozone, a respiratory irri- tant. In addition, "isoprene causes higher levels of atmospheric aero- sol production, which reduces the amount of direct sunlight reaching the earth (a cooling effect), and it causes the global warming poten- tial of methane in the atmosphere to increase (a warming effect). e warming effect is most likely greater than the cooling effect. e net effect of emitted isoprene is to worsen respiratory health and, most likely, warm the atmosphere." Genetic modifications for isoprene suppression During the study, poplars were genetically modified using RNA interference so they would not produce isoprene, then tested in three- and four-year trials at plan- tations in Oregon and Arizona. e genetic tools for modifying the trees, and the protein analyses that revealed changes in the use of biochemical pathways, were devel- oped by scientists at the Institute of Biochemical Plant Pathology, Helmholtz Research Center in Munich, Germany. continued on page 31 Mature poplar trees at a commercial plantation

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