Effects of drought and canopy ozone exposure on antioxidants in fine roots of mature European beech (Fagus sylvatica)
Kristine Haberer (1), Karin Herbinger (2), Maria Alexou (1), Heinz Rennenberg (1) and Michael Tausz (2, 3, 4)
1. Institute of Forest Botany and Tree Physiology, Chair of Tree Physiology, Albert-Ludwigs-University, Georges-Köhler-Allee
053/054, D-79110 Freiburg, Germany / 2. Department for Plant Sciences, Karl-Franzens-University of Graz, Schubertstraße 51, A-8010 Graz, Austria / 3. Present address: School of Forest and Ecosystem Science, University of Melbourne, Water Street, Creswick, Victoria 3363, Australia / 4. Corresponding author () / Received August 2, 2007; accepted October 1, 2007; published online March 3, 2008
Summary
We quantified ascorbate, glutathione and α-tocopherol in fine roots of mature Fagus sylvatica L. under free-air canopy ozone (O3) exposure (twice ambient O3 concentration, 2×[O3]) during two growing seasons that differed in the extent of summer drought (exceptional drought year 2003, average year 2004).
This design allowed us to test whether O3 exposure or drought, or both, affected root antioxidants during the growing season. In both years, root ascorbate and α-tocopherol
showed a similar relationship with volumetric soil water content (SWC): ascorbate concentrations on a root dry mass basis
increased from about 6 to 12 µmol g–1 when SWC dropped from 25 to 20%, and a-tocopherol increased from 100 to 150 nmol g–1 at SWC values below 20%. Root glutathione showed no relationship with SWC or differences between the dry and the average
year, but it was significantly and consistently diminished by 2×[O3]. Our results were inconclusive as to whether shoot–root translocation of glutathione or glutathione production in the roots
was diminished. Phloem glutathione concentrations in the canopy remained constant, but reduced transport velocity in the phloem
and, as a consequence, reduced mass flow of glutathione cannot be ruled out.
