XVI International Botanical Congess

Mediterranean oaks are isoprene, monoterpene or non-emitters. The emission matches oak taxonomy. Monoterpene emitters belong to the subgenus Sclerophyllodrys. The widespread Quercus ilex emits 14 monoterpenes. a-pinene, sabinene, b-pinene and myrcene, make > 70% of the emission, are rapidly labeled with 13C, and are only made by photosynthetic carbon. Other monoterpenes are labeled slowly or incompletely. Monoterpenes contained in the leaves are labeled less than the emitted monoterpenes. Therefore, a secondary C source contributes to form monoterpenes. Monoterpene content reflects qualitatively but not quantitatively the emission. Soluble monoterpene emission is low but the content is relevant. Thermotolerance of Q. ilex, and of the non-emitter Q. suber, slightly improved in leaves fumigated with monoterpenes. Monoterpenes, as other isoprenoids, may have a protective action.