Diversity and Interrelations Among the Constitutive VOC Emission Blends of Four Broad-Leaved Tree Species at Seedling Stage

Abstract

Volatile organic compounds (VOCs) emitted by plants consist of a broad range of gasses which serve purposes such as protecting against herbivores, communicating with insects and neighboring plants, or increasing the tolerance to environmental stresses. Evidence is accumulating that the composition of VOC blends plays an important role in fulfilling these purposes. Constitutional emissions give insight into species-specific stress tolerance potentials and are an important first step in linking metabolism and function of co-occurring VOCs. Here, we investigate the blend composition and interrelations among co-emitted VOCs in unstressed seedlings of four broad-leaved tree species, Quercus robur, Fagus sylvatica, Betula pendula, and Carpinus betulus. VOCs of Q. robur and F. sylvatica mainly emitted isoprene and monoterpenes, respectively. B. pendula had relatively high sesquiterpene emission; however, it made up only 1.7% of its total emissions while the VOC spectrum was dominated by methanol (∼72%). C. betulus was emitting methanol and monoterpenes in similar amounts compared to other species, casting doubt on its frequent classification as a close-to-zero VOC emitter. Beside these major VOCs, a total of 22 VOCs could be identified, with emission rates and blend compositions varying drastically between species. A principal component analysis among species revealed co-release of multiple compounds. In particular, new links between pathways and catabolites were indicated, e.g., correlated emission rates of methanol, sesquiterpenes (mevalonate pathway), and green leaf volatiles (hexanal, hexenyl acetate, and hexenal; lipoxygenase pathway). Furthermore, acetone emissions correlated with eugenol from the Shikimate pathway, a relationship that has not been described before. Our results thus indicate that certain VOC emissions are highly interrelated, pointing toward the importance to improve our understanding of VOC blends rather than targeting dominant VOCs only.

Volatile organic compounds as mediators of plant communication and adaptation to climate change

“…The effects of climate change factors on the production and emission of VOCs into the atmosphere have recently been demonstrated, which could impact their ecological and biological activities (Sun et al, 2022). According to modeling research, tropospheric O 3 levels could restrict the maximal downwind distance of highly reactive flower smells from kilometers in pre-industrial times to <200 m due to currently high pollution levels (Fitzky et al, 2021).…”

“…The effects of climate change factors on the production and emission of VOCs into the atmosphere have recently been demonstrated, which could impact their ecological and biological activities (Sun et al, 2022). According to modeling research, tropospheric O 3 levels could restrict the maximal downwind distance of highly reactive flower smells from kilometers in pre‐industrial times to <200 m due to currently high pollution levels (Fitzky et al, 2021). Under high CO 2 conditions, Quercus ilex produced less monoterpenes (such as, alpha‐pinene, sabinene, and beta‐pinene), probably due to suppressed monoterpene synthases accountable for the production of these compounds, while the emission of limonene (monoterpene) was increased and correlated to higher limonene synthase activity (Hantson et al, 2017; Trivedi et al, 2022).…”

“…Plants release more than 30,000 different biogenic VOCs into the atmosphere, including terpenoids (iso-, mono-, and sesquiterpenes), oxygenated chemical species (ethanol, acetone, methanol, and acetaldehyde), and green leaf volatiles such as hexenals (Fitzky et al, 2021).…”

“…Together, plant VOCs play crucial roles in plant survival and successful reproduction in natural habitats, and have a great impact on both agriculturally-and commercially-relevant characteristics (Fitzky et al, 2021;Rauschkolb et al, 2022). Furthermore, several VOCs have been utilized in flavoring, cosmetics, perfumes, pharmaceutical, and biofuel industries.…”

“…Plants release more than 30,000 different biogenic VOCs into the atmosphere, including terpenoids (iso‐, mono‐, and sesquiterpenes), oxygenated chemical species (ethanol, acetone, methanol, and acetaldehyde), and green leaf volatiles such as hexenals (Fitzky et al, 2021). Isoprene constitutes 44% of all biogenic VOCs released, and monoterpenes and methanol each account for 11% of total VOC emissions, while sesquiterpenes and a variety of other chemicals are frequently emitted at lower levels (Niinemets et al, 2013).…”