Constitutive versus heat and biotic stress induced BVOC emissions in Pseudotsuga menziesii

Induced volatiles have been a focus of recent research, as not much is known of their emission behavior or atmospheric contribution. BVOC emissions were measured from Pseudotsuga menziesii saplings under natural environmental conditions, using a dynamic branch enclosure system and GC–MS for their analysis. We determined temperature and light dependency of the individual compounds, studied seasonality of the emissions and discuss the effect of heat stress in comparison with two specific biotic stresses that occurred naturally on the trees.A standardized emission rate of 6.8 μg g(dw)−1 h−1 for monoterpenes under stressed conditions was almost a magnitude higher than that obtained for healthy trees (0.8 ± 0.2 μg g(dw)−1 h−1), with higher beta factors characterizing the stressed trees. The response of the emissions to light intensity was different for the individual compounds, suggesting a distinct minimum light intensity to reach saturation. Heat stress changed the relative contribution of specific volatiles, with larger extent of increase of sesquiterpenes, methyl salicylate and linalool emissions compared to monoterpenes. Biotic stress kept low the emissions of sesquiterpenes, (E)-4,8-dimethyl-1,3,7-nonatriene and methylbutenol isomers, and increased the level of methyl salicylate and monoterpenes. The ratio of β-pinene/α-pinene was also found to be significantly enhanced from 1.3 to 2.4 and 3.2 for non-stressed, heat stressed and combined biotic and heat stressed, respectively.

Graphical abstractEmissions of biogenic volatile organic compounds were characterized from (a) healthy, (b) aphid infested and (c) a severely diseased (with symptoms similar to Phytophthora spp.) Pseudotsuga menziesii trees.Figure optionsDownload full-size imageDownload high-quality image (125 K)Download as PowerPoint slideHighlights► MT emission under stress was a magnitude higher than obtained for healthy trees. ► Ratio of β-pinene/α-pinene was enhanced under stress, among other compound ratios. ► Saturated emission rates were observed at different light intensities for compounds.