Diversification of terpenoid emissions proposes a geographic structure based on climate and pathogen composition in Japanese cedar.

Biogenic volatile organic compounds emitted from plants are important constituents of atmospheric chemistry and play a major role in the resistance of plants against various environmental stresses. However, little is known about how abiotic and biotic environments on a geographic scale relate to diversifications of the emission. Here, we present variations of terpenes stored in and emitted from leaves of a single species in a common garden, using genetically differentiated local populations of Japanese cedar, the most dominant and widely distributed tree species in Japan. Furthermore, we determined the composition of fungal communities in 50 locations, based on the presence or absence of 158 fungal species inhabiting the cedar. The results showed that terpenoids, especially those that are emitted, were highly diversified and geographically structured among the 12 populations. The total amount of stored terpenes was negatively affected by warm and less-snow climates. On the other hand, variations in some emitted terpenoid species among the populations were correlated to antagonistic fungal species inhabiting the Japanese cedar. We propose that the diversification of composition and amount of stored and emitted terpenoids in the tree species is not only structured by climate, but also antagonistic fungal communities through biological interactions.

Determination and potential importance of diterpene (kaur-16-ene) emitted from dominant coniferous trees in Japan.

Reactive volatile organic compounds (VOCs) are known to affect atmospheric chemistry. Biogenic VOCs (BVOCs) have a significant impact on regional air quality due to their large emission rates and high reactivities. Diterpenes (most particularly, kaur-16-ene) were detected in all of the 205 enclosure air samples collected over multiple seasons at two different sites from Cryptomeria japonica and Chamaecyparis obtusa trees, the dominant coniferous trees in Japan,. The emission rate of kaur-16-ene, was determined to be from 0.01 to 7.1 µg dwg(-1) h(-1) (average: 0.61 µg dwg(-1) h(-1)) employing branch enclosure measurements using adsorbent sampling followed by solid phase-liquid extraction techniques. The emission rate was comparable to that of monoterpenes, which is known major BVOC emissions, collected from the same branches. In addition, total emission of kaur-16-ene at 30°C was estimated to exceed that of total anthropogenic VOC emissions.