Kranzberg Forest Experiment: Differences in gas exchange and antioxidative compounds between young and adult beech trees at the branch and tree level exposed to defined ozone regimes Karin Herbinger 1*, Christiane Then 2,3**, Klaus Remele 1, Dieter Grill 1, Gerhard Wieser 2 & Michael Tausz 1,4 *First speaker **Second speaker 1 Institute of Plant Sciences, University of Graz, Austria 2 Federal Office and Research Centre for Forests, Department of Forest Tree Physiology, Innsbruck, Austria 3 Ecophysiology of Plants, WZW, Technische University of Munich, Freising, Germany 4 School of Forest and Ecosystem Science, University of Melbourne, Creswick, Australia

Background ●Many studies on O 3 effects have been carried out on seedlings under controlled laboratory conditions or in OTC. But it is difficult to transfer these results to predict O 3 responses of adult trees in the field. This is because… - microclimatic conditions are not the same as in the field - ozone sensitivity of young and old trees is different because of morphological and physiological differences between old and young trees ●Further it is still unclear if O 3 effects observed in branch cuvette O 3 fumigation experiments are representative for entire adult trees

Are beech seedlings good surrogates for ozone response of adult trees? I. comparison seedlings vs. adult trees under the same microclimatic conditions

Are cuvette branches surrogates for ozone response of entire trees? II. cuvette vice versa experiment

Investigations Gas exchange measurements –Net photosynthesis –Stomatal conductance Biochemistry –Ascorbate system –Glutathione system –  -Tocopherol –Photoprotective pigments –Carbohydrates

α-Tocopherol

Chlorophyll a+b *

Seedlings versus adult trees Adult tree = 100% *denotes significant (p<0.05) differences between seedlings and adult trees Sun crown 2004

Seedlings versus adult trees Adult tree = 100% Sun crown 2003 *denotes significant (p<0.05) differences between seedlings and adult trees

Seedlings versus adult trees Adult tree = 100% Shade crown 2004 *denotes significant (p<0.05) differences between seedlings and adult trees

Seedlings versus adult trees Adult tree = 100% Shade crown 2003 *denotes significant (p<0.05) differences between seedlings and adult trees

2xO 3 versus 1x O 3 Sun crown xO 3 = 100% *denotes significant (p<0.05) differences between 1xO 3 and 2xO 3

2xO 3 versus 1x O 3 Sun crown xO 3 = 100% *denotes significant (p<0.05) differences between 1xO 3 and 2xO 3

Shade crown xO 3 versus 1x O 3 1xO 3 = 100% *denotes significant (p<0.05) differences between 1xO 3 and 2xO 3

2xO 3 versus 1x O 3 Shade crown xO 3 = 100% *denotes significant (p<0.05) differences between 1xO 3 and 2xO 3

Seedlings versus adult trees Seedlings differ from adult trees in gas exchange measurements, pigments and antioxidants. Shade leaves differ from sun leaves. Significant ozone effects only in shade leaves. Even under comparable site conditions seedlings are uncertain surrogates for ozone response of adult trees. Summary

Are cuvette branches surrogates for ozone response of entire trees? II. cuvette vice versa experiment

Are O 3 effects observed in former branch cuvette O 3 fumigation experiments representative for entire adult trees ? Test: the relevance of branch cuvette experiments as a tool for whole tree reactions to O 3 Does biochemical defense metabolism (antioxidants) of cuvette twigs differ from twigs outside the cuvettes ? Or do cuvette twigs profit from the defense capacity of neighbouring crown parts as a whole tree response? Questions

1xO 3 2xO 3 vice versa – experimental set up

2 x O 3 1xO 3 Kranzberg Forest – free air O 3 fumigation

cuvette position in the sun crown

branch cuvette fumigation

Gas exchange measurements in situ standardised conditions ambient CO 2 20 °C leaf temperature 10 Pa kPa -1 VPD LA light saturation Pigments + antioxidants Carbohydrates (data not shown) Stable isotope ratios (data not shown) measurements performed in was an extremely dry year ! …at the end of the fumigation period:

Results gas exchange trees vs. cuvettes 1xO 3 2xO 3

1xO 3 2xO 3 Results pigments trees vs. cuvettes

1xO 3 2xO 3 Results Antioxidants Xanthophylls trees vs. cuvettes

Irrespective of O 3 exposure cuvette enclosure does not affect gas exchange behaviour, pigments and antioxidant contents in leaves of adult trees O 3 effects similar inside and outside the cuvettes Antioxidant contents further indicate that: Twigs seem to possess autonomy in their defense metabolism This has to be confirmed by other methods….. Conclusions

Thus, our measurements confirm that: Branch cuvette O 3 experiments are relevant for whole-tree risk assessment in adult trees Cuvette branches are good surrogates for adult trees Seedlings are more sensitive to O 3 than adult trees Seedlings are uncertain surrogates for adult trees Conclusions Part I + II

1xO 3 2xO 3 cuvettes with same O 3 regime as outside

Poster: Dose- response relationships

Thank you