Development of a reliable method to determine monoterpene emission rate of plants grown in an open-top chamber

To measure monoterpene emissions from plants grown in widely used open-top chambers (OTCs), we developed a gas sampling method that does not involve the stimulation of leaves and branches. Four clones of Japanese cedar (Cryptomeria japonica) were grown in the OTC (60 x 60 x 120 cm). To sample the monoterpenes, the existing OTC was used for a dynamic enclosure system. The open side (top) of the OTC was covered using a transparent acrylic plate with a hole (10 cm in diameter) in the center. Purified air was supplied through 50 holes (3 mm in diameter) made in a ring-shaped Teflon tube horizontally fixed near the bottom of the OTC. Monoterpene emission rates measured during the afternoon (n = 8-10) were well correlated with temperature (r(2) = 0.94 - 1.00), and the total monoterpene emission rate during a certain period of the experiment can be estimated using this relationship and recorded temperature. Our results suggest that the developed gas sampling system using the existing OTC is a reliable method to collect monoterpenes emitted from plants without stimulating leaves and branches. It can be used to compare the monoterpene emission potential of plants affected by environmental stresses applied for OTC experiments.