Influence of environmental factors and air composition on the emission of alpha-pinene from Quercus ilex leaves

We studied the emission of alpha-pinene from Quercos ilex leaves. Only the abaxial side of the hypostomatous Q. ilex leaf emits alpha-pinene. Light induced photosynthesis and alpha-pinene emission. However, the response of photosynthesis to dark-to-light transitions was faster than that of alpha-pinene, suggesting that ATP controls the emission. The emission was higher at 30 than at 20 degrees C, whereas photosynthesis did not change. Therefore, the relationship between photosynthesis and alpha-pinene emission does not always hold. When CO2 was removed from the air, transpiration was stimulated but photosynthesis and alpha-pinene emission were inhibited. alpha-Pinene inhibition was more rapid under low O-2. When CO2 in the air was increased, photosynthesis was stimulated and transpiration was reduced, but alpha-pinene emission was unaffected. Therefore, the emission depends on the availability of photosynthetic carbon, is not saturated at ambient CO2, and is not dependent on stomatal opening. The pattern of alpha-pinene emission from Q. ilex is different from that of plants having specialized structures for storage and emission of terpenes. We suggest that alpha-pinene emitted by Q. ilex leaves is synthesized in the chloroplasts and shares the same biochemical pathway with isoprene emitted by isoprene-emitting oak species.