Diagnostics in beech exposed to chronic free-air O 3 fumigation: Ozone uptake and gas exchange responses of adult trees Markus Löw, A. J. Nunn, C. Heerdt, K.-H. Häberle and R. Matyssek

Climatic data drought period of 2003 Pre dawn water potential (branches sun crown): -1.4 MPa C. Heerdt

Photosynthesis Error bars indicate standard error Sun crown

Stomatal conductance gH 2 O Error bars indicate standard error Sun crown *** ** Ozone effect disappeared during drought

Stomatal conductance gH 2 O sun – sha 2004 Error bars indicate standard error Sun & Sha crown *** **

Nighttime conductance gH 2 O Error bars indicate standard deviation Risk of O 3 injury during night is not to be neglected.

Ozone data comparison ~50% increase ~100% increase Calculation based on length of growing season! Risk assessment: High „ozone threat“ in 2003?

Ozone data comparison ~50% increase ~100% increase ~ % decrease Due to low stomatal conductance leaves are protected from high ozone threat.

Ozone data 2003 ? ?

Imaging PAM Portable - can be used in the tree crowns assess fluorescence parameters on an area basis non invasive stress response diagnosis visible leaf area 8,84 cm 2 to 0,15 cm 2 (max. Magnification 40x)

Area calculation and quantification Histogram: Image segmentation: 5 classes

Time course May 12, June 22, August 7, September 9

Time course II May 14, June 30, August 8, September 7 Overall 12 “incomplete” time lines, but 8 leaves could be followed throughout the season

Validation by microscopy Picture by P. Vollenweider, WSL (CH) Validated as ozone stipple But – which stipple is it?

Microspcopy + IPAM

Conclusions I The high ozone regime in 2003 increased SUM0 and AOT40 strikingly. In 2003 stomatal conductance and photosynthesis were low because of the dry summer. Stomatal conductance showed a significant decrease under 2xO3 conditions in 2004.

Conclusions II trees were more affected by drought than by ozone in 2003 Drought protected the leaves from severe damages by high ozone concentrations as stomata were closed. Ozone influx was significantly lower in 2003 than in humid years. High ozone concentrations per se do not cause injuries under dry conditions.

Thank You!

Black

Conductance gH 2 O Error bars indicate standard error Ozone effect decreases with prolonged drought humid yeardrought period