Laboratory and field measurements of enantiomeric monoterpeneemissions as a function of chemotype, light and temperature

[摘要] Plants emit significant amounts of monoterpenes into theearth's atmosphere, where they react rapidly to form a multitude of gas phasespecies and particles. Many monoterpenes exist in mirror-image forms orenantiomers. In this study the enantiomeric monoterpene profile for severalrepresentative plants (Quercus ilex L., Rosmarinus officinalis L.,and Pinus halepensis Mill.) was investigated as a function ofchemotype, light and temperature both in the laboratory and in the field.Analysis of enantiomeric monoterpenes from 19 Quercus ilexindividuals from Southern France and Spain revealed four regiospecificchemotypes (genetically fixed emission patterns). In agreement with previouswork, only Quercus ilex emissions increased strongly with light.However, for all three plant species no consistent enantiomeric variation wasobserved as a function of light, and the enantiomeric ratio of α-pinene was found to vary by less than 20% from 100 and1000 μmol m⁻² s⁻¹ PAR (photosynthetically activeradiation). The rate of monoterpene emission increased with temperature fromall three plant species, but little variation in the enantiomericdistribution of α-pinene was observed with temperature. There wasmore enantiomeric variability between individuals of the same species thancould be induced by either light or temperature. Field measurements ofα-pinene enantiomer mixing ratios in the air, taken at aQuercus ilex forest in Southern France, and several other previouslyreported field enantiomeric ratio diel cycle profiles are compared. All showsmoothly varying diel cycles (some positive and some negative) even overchanging wind directions. This is surprising in comparison with variations ofenantiomeric emission patterns shown by individuals of the same species.

[学科分类] 地球化学与岩石