Drought and salt are key abiotic stressors in temperate cities. Biogenic volatile organic compound (BVOC) emissions, often dominated by trees, influence the urban troposphere and mediate plant-plant and plant-insect interactions. While knowledge on constitutive BVOC emissions is increasing, modulation of blends by stress has yet received little attention. We thus investigated BVOC blends and herbivore-related subsets (‘bouquets’) of Quercus robur, Fagus sylvatica, Betula pendula and Carpinus betulus seedlings under control, and after 2-weeks of drought and salt stress using PTR-Tof-MS. 22 BVOCs were related to metabolic pathways, and changes among blends and bouquets were assessed. Drought led to a slight increase of isoprene and monoterpene emissions from Q. robur and F. sylvatica, respectively, while total non-isoprene emissions generally declined under water stress. Both drought and salinity led to distinct, species-specific changes in the emission rates of single BVOCs, and resulted in markedly different herbivore-related bouquets in F. sylvatica and C. betulus. Oxygenated VOCs and green leaf volatiles in particular increased in these two salt-sensitive species, while pathway-specific effects were less clear under drought. Findings indicate significant consequences of common urban stressors on BVOC emission spectra, including tropospheric ozone formation and severely hampered plant communication cues under stress.

干旱和盐分是温带城市的主要非生物压力因素。生物挥发性有机化合物 (BVOC) 排放通常以树木为主，影响城市对流层并调节植物与植物和植物与昆虫的相互作用。虽然对组成型 BVOC 排放的了解不断增加，但通过压力调节混合物却很少受到关注。因此，我们研究了Quercus robur、Fagus sylvatica、Betula pendula和Carpinus etulus 的 BVOC 混合物和食草动物相关子集（“花束”）使用 PTR-Tof-MS 控制幼苗，并在干旱和盐胁迫 2 周后。22 种 BVOC 与代谢途径相关，并评估了混合物和香味之间的变化。干旱分别导致Q. robur和F. sylvatica的异戊二烯和单萜排放量略有增加，而非异戊二烯排放总量在水分胁迫下普遍下降。干旱和盐度都会导致单一 BVOC 排放率发生明显的物种特异性变化，并导致F. sylvatica和C. betulus中与食草动物相关的花束明显不同. 在这两个对盐敏感的物种中，含氧 VOC 和绿叶挥发物尤其增加，而在干旱条件下，特定途径的影响不太明显。研究结果表明，常见的城市压力源对 BVOC 排放光谱产生了重大影响，包括对流层臭氧的形成和压力下植物交流线索的严重受阻。