Measurement of isoprenoid content in leaves of Mediterranean Quercus spp. by a novel and sensitive method and estimation of the isoprenoid partition between liquid and gas phase inside the leaves

We used a novel. simple and sensitive method to extract isoprenoids contained in the leaves and compared emission and content of isoprenoids in the leaves of three Mediterranean oak species emitting isoprene (Quercus puhcsccws), monoterpenes (Querc~s ilrs) or non-emitting isoprenoids (Quercus cerris). The content is qualitatively consistent with the emission of isoprenoids by Qucrczls spp. However. the fraction of isoprenoids in the gas phase was estimated to be r 0.02 and 5% of the total content for monoterpenes and isoprene, respectively. On the other hand, the content of monoterpenes in the leaf was much higher than that of isoprene and particularly rich of compounds which can hardly be detected in an emission such as linalool. It is concluded that isoprenoids are contained in temporary pools and that the different partition between gas and liquid phases plays an important role in determining the pool size in isoprene and monoterpene-emitting oaks. The pools of isoprenoid-emitting oaks sustain the emission for few minutes when isoprenoid formation is prevented. which rules out the presence of specialized organs for isoprenoid storage and are absent altogether in non-emitting species.