Indicators of ozone effects on Fagus sylvatica L

In this paper optical indices calculated from leaf reflectance measurements, acquired with a high resolution spectroradiometer, were investigated to monitor 03 stress on Fagus sylvatica L. from the strain phase to the damage phase when visible symptoms occur (e.g. chlorosis, leaf browning). The CI (Chlorophyll Index) was the most sensible index to a wide range of chlorophyll (Chl) concentrations (R(2)=0.93), the simple ratio R(695)/R(740) (Ctr2) was the most correlated to carotenoids/chlorophyll (Car/Chl) ratio (R(2)=0.65), while Yl (Yellowness Index) was sensible to Car/Chl ratio and to low Chl values but tends to saturate at moderate to high Chl concentrations. PRI (Photochemical Reflectance Index) was correlated with the physiological parameters NPQ (Non Photochemical Quenching) and Delta F/F(m)' confirming this index is a good indicator of photosynthetic efficiency. Results from this experiment showed that Cl, Ctr2 and PRI were reliable indices of 03 effects on Fagus sylvatica L. before visible symptoms occurred, while Yl was able to detect the senescence anticipation when visible symptoms already spread. These results were confirmed by physiological parameters measured in field (F(v)/F(m), NPQ and Delta F/F(m)').