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

Abstract

We studied the emission of α-pinene from Quercus ilex leaves. Only the abaxial side of the hypostomatous Q. ilex leaf emits α-pinene. Light induced photosynthesis and α-pinene emission. However, the response of photosynthesis to dark-to-light transitions was faster than that of α-pinene, suggesting that ATP controls the emission. The emission was higher at 30 than at 20°C, whereas photosynthesis did not change. Therefore, the relationship between photosynthesis and α-pinene emission does not always hold. When CO2 was removed from the air, transpiration was stimulated but photosynthesis and α-pinene emission were inhibited. α-Pinene inhibition was more rapid under low O2. When CO2 in the air was increased, photosynthesis was stimulated and transpiration was reduced, but α-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 α-pinene emission from Q. ilex is different from that of plants having specialized structures for storage and emission of terpenes. We suggest that α-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.