Isoprenoid emission in trees of Quercus pubescens and Quercus ilex with lifetime exposure to naturally high CO₂ environment^†

Abstract

The long-term effect of elevated atmospheric CO 2 on isoprenoid emissions from adult trees of two Mediterranean oak species (the monoterpene-emitting Quercus ilex L. and the isoprene-emitting Quercus pubescens Willd.) native to a high-CO 2 environment was investigated. During two consecutive years, isoprenoid emission was monitored both at . Long-term exposure to high atmospheric levels of CO 2 did not significantly affect the actual isoprenoid emissions. However, when leaves of plants grown in the control site were exposed for a short period to an elevated CO 2 level by rapidly switching the CO 2 concentration in the gas-exchange cuvette, both isoprene and monoterpene basal emissions were clearly inhibited. These results generally confirm the inhibitory effect of elevated CO 2 on isoprenoid emission. The absence of a CO 2 effect on actual emissions might indicate higher leaf temperature at elevated CO 2 , or an interaction with multiple stresses some of which (e.g. recurrent droughts) may compensate for the CO 2 effect in Mediterranean ecosystems. Under elevated CO 2 , isoprene emission by Q. pubescens was also uncoupled from the previous day's air temperature. In addition, pronounced daily and seasonal variations of basal emission were observed under elevated CO 2 underlining that correction factors may be necessary to improve the realistic estimation of isoprene emissions with empirical algorithms in the future. A positive linear correlation of isoprenoid emission with the photosynthetic electron transport and in particular with its calculated fraction used for isoprenoid synthesis was found. The slope of this relationship was different for isoprene and monoterpenes, but did not change when plants were grown in either ambient or elevated CO 2 . This suggests that physiological algorithms may usefully predict isoprenoid emission also under rising CO 2 levels.

History effect of light and temperature on monoterpenoid emissions from Fagus sylvatica L.

“…Moreover, they appear also to depend on light and temperature levels experienced by the plant in the previous hours, days or even weeks. The dependence on temperature during previous days or weeks has been observed in the case of isoprene (Monson et al, 1994;Sharkey et al, 1999;Pétron et al, 2001;Rapparini et al, 2004) and 2-methyl-3-buten-2-ol (MBO) (Gray et al, 2003(Gray et al, , 2006. This dependence is apparently due to changes in the concentration of enzymes responsible for the production of these compounds (Schnitzler et al, 1997) and is consistent with their hypothesized role as thermal protectant (Sharkey et al, 2008).…”

Changes in Monoterpene Emission Rates of Quercus ilex Infested by Aphids Tended by Native or Invasive Lasius Ant Species

“…that emit mainly isoprene (Kesselmeier and Staudt 1999). The blend produced by holm oak has been studied mainly in relation to its modulation by abiotic factors (temperature, light, drought, different CO 2 concentrations) (Staudt and Bertin 1998;Llusia and Peñuelas 1999;Rapparini et al 2004;Peñuelas and Staudt 2010). In accordance with previous reports of holm oak terpene emissions, we found that the blend produced by holm oak saplings was composed mainly of α-and β-pinene, sabinene and myrcene (Street et al 1997;Staudt and Bertin 1998).…”

The use of branch enclosures to assess direct and indirect effects of elevated CO2 on photosynthesis, respiration and isoprene emission of Populus alba leaves

“…It is interesting to observe that many exper iments in which the inhibition of isoprene by elevated CO2 was not observed, were based on branch enclosure long-term measure ments (e.g., Rapparini et al 2004). We there fore also put forward the suggestion that branch enclosures strongly and independent ly affect many physiological features, and do not offer representative indications of the ac tual impact of elevated CO2 on primary and secondary carbon metabolism in nature.…”