SIMULTANEOUS FIELD-MEASUREMENTS OF TERPENE AND ISOPRENE EMISSIONS FROM 2 DOMINANT MEDITERRANEAN OAK SPECIES IN RELATION TO A NORTH-AMERICANSPECIES

We investigated the emission of monoterpenes and isoprene from tree sp ecies growing at a site near Montpellier (South France). We compared t he emission pattern and behaviour of two important oak species represe ntative of the Mediterranean ecosystem, namely, Quercus ilex (Holm oak ), a strong monoterpene emitter, and Quercus pubescens (White oak), a strong isoprene emitter by measuring the two species growing side by s ide simultaneously. Additionally, we included a Californian oak specie s Quercus agrifolia (Coast Live Oak), which is anatomically and morpho logically comparable with Quercus ilex. The data show that Live Oak an d Helm oak though they appear identical, differ as far as the emission of terpenoids is concerned, emitting isoprene or terpenes, respective ly. The isoprene emitting White oak and the monoterpene emitting Helm oak react identically to the same environmental conditions, fluctuatin g light and temperature, indicating that close metabolic pathways are involved in the actual emission of the C5 and C10 compounds from these two species, as seen under field conditions. (C) 1998 Elsevier Scienc e Ltd. All rights reserved.