BIOGENIC EMISSIONS AND CO2 GAS-EXCHANGE INVESTIGATED ON 4 MEDITERRANEAN SHRUBS

In order to investigate the impact of plant physiology on emissions of biogenic volatile organic compounds monoterpene emission rates from R osmarinus officinalis (L.) and Pistacia lentiscus (L.) and isoprene em ission rates from Erica arborea (L.) and Myrtus communis (L.) were det ermined. The study, an activity in the framework of BEMA (Biogenic Emi ssions in the Mediterranean Area), was carried out in May 1994 at Cast elporziano near Rome in Italy, using a dynamic enclosure technique com bined with recording CO2 gas exchange, temperature and irradiance data . The monoterpenes dominating the emission pattern were 1,8-cineol, al pha-pinene and beta-pinene for rosemary and alpha-pinene, linalool and beta-pinene + sabinene for pistachio. Total monoterpene emission rate s standardized to 30 degrees C of 1.84 +/- 0.24 and 0.35 +/- 0.04 mu g C g(-1) dw h(-1) were found for rosemary and pistachio, respectively (on a leaf dry weight basis). Myrtle emitted 22.2 +/- 4.9 mu g C g(-1) dw h(-1) at standard conditions (30 degrees C, PAR 1000 mu mol photon s m(-2) s(-1)) as isoprene and erica 5.61 mu g C g(-1) dw h(-1). The c arbon loss due to terpenoid emissions per photosynthetically carbon up take was about 0.01-0.1% for the monoterpene emitters. The isoprene em itting shrubs lost 0-0.9% of the assimilated carbon. The rapid inducti on of emissions in the sun after temporary shading indicates that isop rene emissions were closely linked to photosynthesis. A higher proport ion of the assimilated carbon was lost as isoprene under conditions of high light and temperature compared to the morning and evening hours. (C) 1997 Elsevier Science Ltd.