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 co ntained in the leaves and compared emission and content of isoprenoids in the leaves of three Mediterranean oak species emitting isoprene (Q uercus pubescens), monoterpenes (Quercus ilex) or non-emitting isopren oids (Quercus cerris). The content is qualitatively consistent with th e emission of isoprenoids by Quercus spp, However, the fraction of iso prenoids in the gas phase was estimated to be approximate to 0.02 and 5% of the total content for monoterpenes and isoprene, respectively. O n the other hand, the content of monoterpenes in the leaf was much hig her than that of isoprene and particularly rich of compounds which can hardly be detected in an emission such as linalool, It is concluded t hat isoprenoids are contained in temporary pools and that the differen t partition between gas and liquid phases plays an important role in d etermining the pool size in isoprene and monoterpene-emitting oaks. Th e pools of isoprenoid-emitting oaks sustain the emission for few minut es when isoprenoid formation is prevented, which rules out the presenc e of specialized organs for isoprenoid storage and are absent altogeth er in non-emitting species. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.