Trees emit high levels of isoprene, a hydrocarbon that forms ozone with human-made nitrogen oxides. Warming is worsening the problem.
Should we cut down all the oak trees?” The question is rhetorical, but it has a serious context, because the person asking it—Tom Sharkey, a plant researcher at Michigan State University—has noticed an ominous connection: some trees—especially oaks, but also As warming advances, poplar trees emit much more than they already do of a hydrocarbon that, when combined with nitrogen oxides from factory smokestacks and car exhaust, forms ozone, the gas that protects against UV radiation. high in the atmosphere, but which harms the health of people close to the ground also because of plants: isoprene, C5H8 (Pnas 5. 10.).
This is rarely heard of, it only briefly attracted attention when US President Ronald Reagen rejected any tightening of air pollution control measures in the early 1980s, arguing that “about 80 percent of our air pollution comes from of hydrocarbons emitted by plants. Therefore, let us not exaggerate the standards of human sources” (Sierra 65, p. 15).
It was only late that people realized that the gas was in the air
Two things were true about this: after methane, isoprene is the hydrocarbon that enters the atmosphere most frequently – 600 to 800 million tons per year – and it comes mainly from plants, often from deciduous trees, with oaks topping the trees. poplars. However, the gas – which was discovered in the laboratory in 1860 as a product of the decomposition of rubber – for a long time was not noticed in the atmosphere; Unlike monoterpenes from conifers, we don’t feel it. Guivi Sanadze of Tbilisi University in Georgia was the first to publish about it in 1957. The news did not spread in the West, it was only noticed there in 1965 and aroused little interest – except among researchers. whose findings Reagen referred to – In 1999, a group led by Peter Kaufman (University of Michigan) decreed that “isoprene does not occur in nature” as a “free gas” (Natural Products from Plants p. 343).
This ignorance is over, but the “biology of isoprene is still mysterious.” Thomas Sharkey (Michigan State University) and Russell Monson (University of Arizona) lamented that on the occasion of the 60th anniversary of the publication of Sanadze (Plant, Cell and Environment 40, p. 1671), little has changed in the state of knowledge for today, except that it has been observed that there are also other sources of isoprene: abiotic ones, such as the extremely thin surface film of the seas, a soup of organic molecules (Scientific Reports 5: 12741): and living ones, among them us, who find it in muscles, we produce different amounts depending on the level of stress, then excrete it through our breath and skin: When there is a lot of excitement at the cinema, the levels increase so much – from sliding around in the seats – which a group led by Jonathan Williams (MPI Chemie Mainz) 2018 suggested that the air in the room should be used to decide whether films should be given to children or not (PLoS One e0203044).