Abstract
Abstract. Drought events are expected to become more frequent with climate change. To predict the effect of plant emissions on air quality and potential feedback effects on climate, the study of biogenic volatile organic compound emissions under stress is of great importance. Trees can often be subject to a combination of abiotic stresses, for example due to drought or ozone. Even though there is a large body of knowledge on individual stress factors, the effects of combined stressors are not much explored. This study aimed to investigate changes of biogenic volatile organic compound emissions and physiological parameters in Quercus robur L. during moderate to severe drought in combination with ozone stress. Results show that isoprene emissions decreased while monoterpene and sesquiterpene emissions increased during the progression of drought. We exposed plants with daily ozone concentrations of 100 ppb for 1 h for 7 d, which resulted in faster stomatal closure (e.g., a mean value of −31.3 % at an average stem water potential of −1 MPa), partially mitigating drought stress effects. Evidence of this was found in enhanced green leaf volatiles in trees without ozone fumigation, indicating cellular damage. In addition we observed an enhancement in (C8H8O3)H+ emissions likely corresponding to methyl-salicylate in trees with ozone treatment. Individual plant stress factors are not necessarily additive, and atmospheric models should implement stress feedback loops to study regional-scale effects.
Highlights
Plants, in both natural and managed ecosystems, release biogenic volatile organic compounds (BVOCs), covering over 30 000 known compounds (Peñuelas and Llusiá, 2004)
This shows that trees of drought stress (DS) × OS closed their stoma quickly at higher stem water potential after the first ozone fumigation session and confirms what was reported in other studies that moderate ozone concentrations can induce partially closed stomata (Khatamian et al, 1973; Farage et al, 1991; Wittig et al, 2007)
The changes in BVOC emissions of Q. robur subject to continuously increasing drought were investigated, and differences in the drought progression were observed in plants with and without ozone fumigation
Summary
In both natural and managed ecosystems, release biogenic volatile organic compounds (BVOCs), covering over 30 000 known compounds (Peñuelas and Llusiá, 2004). These molecules have different physical and chemical characteristics and they differ in their metabolic origins in plants (Peñuelas and Llusiá, 2001; Laothawornkitkul et al, 2009; Maffei, 2010). The estimated global annual flux of IS ranges from 440 to 600 Tg C yr−1 (Guenther et al, 2012) These values correspond to 2 % of the photosynthetically fixed carbon (Lal, 1999) and comprise a significant part of the total annual emission of BVOCs on a global scale of 1150 Tg C (Guenther et al, 1995). BVOCs are thought to play a role in protecting vegetation from abiotic (Peñuelas and MunnéBosch, 2005; Velikova et al, 2005) and biotic stress
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