title: Photosynthetic performance and water relations in young pubescent oak (Quercus pubescens) trees during drought stress and recovery.
abstract: The capability to withstand and to recover from severe summer droughts is becoming an important issue for tree species in central Europe, as dry periods are predicted to occur more frequently over the coming decades. Changes in leaf gas exchange, chlorophyll a fluorescence and leaf compounds related to photoprotection were analysed in young Quercus pubescens trees under field conditions during two summers (2004 and 2005) of progressive drought and subsequent rewatering. Photochemistry was reversibly down-regulated and dissipation of excess energy was enhanced during the stress phase, while contents of leaf pigments and antioxidants were almost unaltered. Plant water status was restored immediately after rewatering. Net photosynthesis (P(n)) measured at ambient CO2 recovered from inhibition by drought within 4 wk. P(n) measured at elevated CO2--to overcome stomatal limitations--was restored after a few days. A network of photoprotective mechanisms acted in preserving the potential functionality of the photosynthetic apparatus during severe drought, leading to a rapid recovery of photosynthetic activity after rewatering. Thus, Q. pubescens seems to be capable of withstanding and surviving extreme drought events.
authors.affiliation: Institute of Plant Sciences, University of Bern, Altenbergrain 21, CH-3013 Bern, Switzerland.
authors.forename: Alexander
authors.initials: A
authors.lastname: Gallé
authors.affiliation: Institute of Plant Sciences, University of Bern, Altenbergrain 21, CH-3013 Bern, Switzerland.
authors.forename: Pierre
authors.initials: P
authors.lastname: Haldimann
authors.affiliation: Institute of Plant Sciences, University of Bern, Altenbergrain 21, CH-3013 Bern, Switzerland.
authors.forename: Urs
authors.initials: U
authors.lastname: Feller
mesh_terms: D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D002980:Climate; D004190:Disasters; D005740:Gases / Q000378:metabolism; D010788:Photosynthesis; D018515:Plant Leaves / Q000502:physiology; D029963:Quercus / Q000254:growth & development / Q000502:physiology*; D013557:Switzerland; D014867:Water / Q000378:metabolism*
chemical_list: D005740:Gases; D014867:Water; D002734:Chlorophyll; D000077194:Chlorophyll A