In-field yellow starthistle (Centaurea solstitialis) volatile composition under elevated temperature and CO2 and implications for future control

Abiotic stressors may affect biogenic volatile organic compounds (BVOCs) involved in plant communication. We examined how certain environmental conditions affect plant signaling via BVOC emission. Specifically, we investigated the effects of elevated CO2 and temperature in situ on BVOCs produced by mechanically damaged leaves of Centaurea solstitialis L. (yellow starthistle), a major invasive weed in western North America, grown in grassland plots in the foothills of northern California. The headspace BVOCs of C. solstitialis were collected in situ by a customized Teflon(A (R)) bag and solid-phase microextraction and analyzed by gas chromatography-mass spectroscopy. Damaging leaves led to the release of 14 volatile compounds, predominantly sesquiterpenes. The co-occurrence of five compound pairs was highly significant across all treatments, which may be explained through synthesis by the same enzyme. We found no significant effect of treatment on the levels of individual or total volatiles. The stability of volatile profile for this invasive under future conditions should therefore (1) not alter indirect defense signaling and (2) support the selection of biological controls on the basis of their specificity to the identified in-field host plant BVOCs.