Comparison of Isoprene Emission, Intercellular Isoprene Concentration and Photosynthetic Performance in Water-Limited Oak (Quercus pubescens Willd. and Quercus robur L.) Saplings |
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Authors: | N Brüggemann J-P Schnitzler |
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Institution: | Institut für Meteorologie und Klimaforschung, Bereich Atmosphärische Umweltforschung (IMK-IFU) Forschungszentrum Karlsruhe, Garmisch-Partenkirchen, Germany (formerly: Fraunhofer-Institut für Atmosphärische Umweltforschung [IFU]) |
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Abstract: | Abstract: The influence of prolonged water limitation on leaf gas exchange, isoprene emission, isoprene synthase activities and intercellular isoprene concentrations was investigated under standard conditions (30 °C leaf temperature and 1000 μmol photons m-2 s-1 PPFD) in greenhouse experiments with five-year-old pubescent oak ( Quercus pubescens Willd.) and four-year-old pedunculate oak ( Quercus robur L.) saplings. Net assimilation rates proved to be highly sensitive to moderate drought in both oak species, and were virtually zero at water potentials (Ψpd) below - 1.3 MPa in Q. robur and below - 2.5 MPa in Q. pubescens . The response of stomatal conductance to water stress was slightly less distinct. Isoprene emission was much more resistant to drought and declined significantly only at Ψpd below - 2 MPa in Q. robur and below - 3.5 MPa in Q. pubescens . Even during the most severe water stress, isoprene emission of drought-stressed saplings was still approximately one-third of the control in Q. robur and one-fifth in Q. pubescens . Isoprene synthase activities were virtually unaffected by drought stress. Re-watering led to partial recovery of leaf gas exchange and isoprene emission. Intercellular isoprene concentrations were remarkably enhanced in water-limited saplings of both oak species during the first half of the respective drought periods with maximum mean values up to ca. 16 μl l-1 isoprene for Q. pubescens and ca. 11 μl l-1 isoprene for pedunculate oak, supporting the hypothesis that isoprene serves as a short-term thermoprotective agent in isoprene-emitting plant species. |
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Keywords: | Drought isoprene emission isoprene synthase oak photosynthesis Quercus pubescens Quercus robur |
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