Study Confirms That Health-Damaging Ground-Level Ozone Formation Can Be Suppressed Without Negative Consequences for Trees
In order not to affect air quality by ground-level ozone formation, certain tree species emitting large quantities of isoprene should not be planted in large numbers in urban and suburban areas. Genetic suppression of isoprene emissions can help to reduce the negative health effects for humans. Researchers at Helmholtz Zentrum München have now been able to prove that this can be done without damaging the tree's biomass production, which in turn can have a positive effect on regional air quality.
Plants emit large quantities of volatile organic compounds (VOCs). Isoprene is one of them. It is found especially in fast-growing tree species, which are cultivated for bio-economic use but also as urban trees. Isoprene is a hydrocarbon compound with high reactivity, which can have a major impact on regional air quality. If isoprene meets nitrogen oxides from car exhaust gases or other combustion processes, the formation of ozone near the ground is increased. Ozone, in turn, can penetrate deep into the human lung and affect the respiratory tract, disrupt heart function and weaken general performance. In order to reduce above mentioned health risks, scientists are conducting research into generating plants with low isoprene emissions without impairing plant fitness and growth. For plants themselves, isoprene is beneficial. For example, the compound can protect plant photosynthesis from thermal and oxidative stress.
Suppressed isoprene emission does not harm trees and protects humans
Using the RNA interference method (RNAi), researchers at Helmholtz Zentrum München in cooperation with the University of Arizona, Oregon State University and Portland State University switched off the isoprene emission from poplars. In order to test a possible effect on their biomass production, long-term field experiments in Oregon and Arizona were conducted. The scientists were able to prove that the genetic suppression of isoprene emission does not significantly affect biomass production. This result is explained by the fact that biomass production is highest at the beginning and end of the growing seasons, which are spring and autumn. During the hot summer months, when isoprene would be beneficial to protect the photosynthesis of the plant, growth stops. The reduced protection of photosynthesis in summer therefore has no negative effect on biomass production.
Prof. Jörg-Peter Schnitzler, Head of the Research Unit of Environmental Simulation at Helmholtz Zentrum München: "The investigations show that isoprene emission in plants can be suppressed without affecting biomass production. This in turn can benefit human health in cities by reducing the potential for ozone formation ".
In future, new genome editing methods such as CRISPR/Cas could be used to suppress isoprene emissions in other widespread bioenergy crops such as willows or reeds and accordingly improve regional air quality.
Scientists from the University of California, Riverside, NASA's Goddard Space Flight Center and the Institute of Microbiology in Greifswald also contributed to the study.
The study was co-financed by the joint project 'PRO-BIOPA' (No. 0315412) of the Federal Ministry of Education and Research (BMBF).
R.K. Monson et al., 2020: <link www.pnas.org/content/early/2020/01/01/1912327117 - extern>High productivity in hybrid-poplar plantations without isoprene emission to the atmosphere. </link>PNAS, DOI: 10.1073/pnas.1912327117