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Front. Plant Sci. | doi: 10.3389/fpls.2018.00187

Resilient leaf physiological response of European beech (Fagus sylvatica L.) to summer drought and drought release

  • 1Forest Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research, Switzerland
  • 2Institute of Agricultural Sciences, ETH Zurich, Switzerland
  • 3Paul Scherrer Institute, Switzerland
  • 4University of Basel, Switzerland
  • 5School of Forest Science and Resource Management, Technische Universität München, Germany

Drought is a major environmental constraint to trees, causing severe stress and thus adversely affecting their functional integrity. European beech (Fagus sylvatica L.) is a key species in mesic forests that is commonly expected to suffer in a future climate with more intense and frequent droughts. Here, we assessed the seasonal response of leaf physiological characteristics of beech saplings to drought and drought release to investigate their potential to recover from the imposed stress and overcome previous limitations. Saplings were transplanted to model ecosystems and exposed to a simulated summer drought. Pre-dawn water potentials (ψpd), stomatal conductance (gS), intercellular CO2 concentration (ci), net-photosynthesis (AN), PSII chlorophyll fluorescence (PItot), non-structural carbohydrate concentrations (NSC; soluble sugars, starch) and carbon isotope signatures were measured in leaves throughout the growing season. Pre-dawn water potentials (ψpd), gS, ci, AN and PItot decreased as drought progressed, and the concentration of soluble sugars increased at the expense of starch. Carbon isotopes in soluble sugars (δ13CS) showed a distinct increase under drought, suggesting, together with decreased ci, stomatal limitation of AN. Drought effects on ψpd, ci and NSC disappeared shortly after re-watering, while full recovery of gS and AN was delayed by one week and full recovery of PItot by two weeks. The fast recovery of NSC was reflected by a rapid decay of the drought signal in δ13C values, indicating a rapid turnover of assimilates and a reactivation of carbon metabolism. After recovery, the previously drought-exposed saplings showed a stimulation of AN and a trend towards elevated starch concentrations, which counteracted the previous drought limitations. Overall, our results suggest that the internal water relations of beech saplings and the physiological activity of leaves are restored rapidly after drought release. In the case of AN, stimulation after drought may partially compensate for limitations on photosynthetic activity during drought. Our observations suggest high resilience of beech to drought, contradicting the general belief that beech is particularly sensitive to environmental stressors.

Keywords: 13C, non-structural carbohydrates, Photosynthesis, Recovery, Water shortage

Received: 14 Aug 2017; Accepted: 31 Jan 2018.

Edited by:

Sebastian Leuzinger, Auckland University of Technology, New Zealand

Reviewed by:

Mauro Centritto, Trees and Timber Institute (CNR), Italy
Fábio M. DaMatta, Universidade Federal de Viçosa, Brazil  

Copyright: © 2018 Pflug, Buchmann, Siegwolf, Schaub, Rigling and Arend. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence:
Prof. Nina Buchmann, ETH Zurich, Institute of Agricultural Sciences, Zurich, Switzerland, nina.buchmann@usys.ethz.ch
Dr. Matthias Arend, Swiss Federal Institute for Forest, Snow and Landscape Research, Forest Dynamics, Birmensdorf, Switzerland, matthias.arend@unibas.ch