Emissions of oxygenated volatile organic compounds from plants - part II: Emissions of saturated aldehydes

Emissions of hexanal, heptanal, octanal, nonanal, and decanal from 6 different plant species were measured in continuously stirred tank reactors when the plants were exposed to ozone. Pathogen- and insect attack on plants also led to these emissions. The emission rates of individual aldehydes were related to each other implying a common mechanism for the emissions of these aldehydes. Furthermore, the emission pattern was similar in all cases indicating a similar emission mechanism for different plant species and different elicitors. Measurements with ozone exposed Scots pine plants (Pinus sylvestris L.) showed that the emission rates were dependent on temperature as well as on the ozone flux into the plants. The diurnal variation of aldehyde emissions from ozone exposed Scots pine were described quite well using a formalism including temperature and ozone flux as variables. Assuming the aldehyde emissions to be general for plants exposed to ozone, the global emissions were estimated to be in the range between 7 and 22 Tg/a. Because these emissions can be induced by other factors than ozone uptake alone this estimate may be a lower limit.