During 1989–1994 the emission rates of VOCs (primarily isoprene and monoterpenes) from various plant species were assessed by different sampling methods, including the use of excised plant material (leaf disc method) and a dynamic flowthrough branch enclosure, developed during the course of this work. Both stressed and unstressed plants have been studied.Various tree (conifer and broadleaf), crop and herbaceous UK species were screened (leaf disc method), as were 19 typical Mediterranean species (enclosure method). All plants sampled with the enclosure method have been screened for their tendency to emit oxygenated compounds (BOVOCs). For example, maize emitted negligible amounts of isoprene and monoterpenes but various aldehydes and ketones.The effects of both elevated ozone (O3) and carbon dioxide (CO2) have been investigated. Elevated ozone levels had an inconclusive effect on emission rates. On the other hand, exposure to elevated levels of CO2 resulted in increased emissions of VOCs.Relationships between environmental conditions and emission rates were studied. Of the UK species, emissions of isoprene from Sitka spruce, gorse and oak, and of monoterpenes from gorse, demonstrated a relationship with temperature. Relationships to the PAR regime were inferred, but not directly quantified, due to the uncontrolled nature of field measurements made under ambient conditions. Monoterpene emissions from the Mediterranean species Quercus ilex demonstrated a better relationship with light than temperature. Emissions from Eucalyptus globulus were exponentially related to temperature.Comparisons between laboratory samples, field samples and different ages of vegetation, have revealed differences in chemical speciation and absolute emission rates, which may be a result of their different growth environments and physiology. It was concluded that extrapolations from a few samples, or those based on laboratory measurements, must be treated with caution.
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- Emissions of VOCs from Stressed and Unstressed Vegetation
R. A. Street
S. C. Duckham
C. N. Hewitt
- Springer Berlin Heidelberg