Abstract
Mediterranean vegetation emits a wide range of biogenic volatile organic compounds (BVOCs) among which isoprenoids present quantitatively the most important compound class. Here, we investigated the isoprenoid emission from two Mediterranean Cistaceae shrubs, Halimium halimifolium and Cistus ladanifer, under controlled and natural conditions, respectively. For the first time, diurnal emission patterns of the diterpene kaurene were detected in real-time by Proton-Transfer-Reaction-Time-of-Flight-Mass-Spectrometer. Kaurene emissions were strongly variable among H. halimifolium plants, ranging from 0.01 ± 0.003 to 0.06 ± 0.01 nmol m−2 s−1 in low and high emitting individuals, respectively. They were in the same order of magnitude as monoterpene (0.01 ± 0.01 to 0.11 ± 0.04 nmol m−2 s−1) and sesquiterpene (0.01 ± 0.01 to 0.52 nmol m−2 s−1) emission rates. Comparable range and variability was found for C. ladanifer under natural conditions. Labelling with 13C-pyruvate suggested that emitted kaurene was not derived from de novo biosynthesis. The high kaurene content in leaves, the weak relationship with ecophysiological parameters and the tendency of higher emissions with increasing temperatures in the field indicate an emission from storage pools. This study highlights significant emissions of kaurene from two Mediterranean shrub species, indicating that the release of diterpenes into the atmosphere should probably deserve more attention in the future.
Highlights
Vegetation is the largest global emission source of biogenic volatile organic compounds (BVOCs) with an estimated 1000 Tg of carbon yr−11, having a profound impact on the atmosphere’s chemistry and biogenic secondary aerosol formation
It is assumed that these compounds are involved in physiological and ecological processes, that most likely contribute to plant survival in such harsh environments[28]. We hypothesize that these characteristic Mediterranean shrubs Cistus ladanifer and Halimium halimifolium emit a wide variety of isoprenoids
We investigated the dynamics of isoprenoid emissions of C. ladanifer and H. halimifolium under natural and controlled conditions, respectively
Summary
Vegetation is the largest global emission source of biogenic volatile organic compounds (BVOCs) with an estimated 1000 Tg of carbon yr−11, having a profound impact on the atmosphere’s chemistry and biogenic secondary aerosol formation. Diterpenes were generally considered as non-volatile compounds, even though first records of emissions in three plant species were reported[19,26,27]. To shed new light on the potential role of the emission of isoprenoids with high molecular weight masses, we selected two Mediterranean shrubs from the Cistaceae family. Considering that these species contain high molecular weight isoprenoids such as diterpenes, we hypothesize that they may emit such large isoprenoids into the atmosphere. To assess these hypotheses, we investigated the dynamics of isoprenoid emissions of C. ladanifer and H. halimifolium under natural and controlled conditions, respectively. A particular emphasis was placed on the emission patterns of high molecular weight compounds, which we discuss in terms of their emission sources, function, and possible ecological relevance
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