840 
In Fig. 7 a daily cycle recorded on maize is shown. The upper panel shows the ratio I(685)/I(/735) 
and the lower I(685)/I(480). It can be seen that the signal-to-noise ratio is just slightlv less in the sinale- 
shot case than in the case of 100 shots integrated. 
blue 470nm 
685nm 740nm 
Fig. 8. Example of multi-colour 
fluorescence imaging for a maize 
plant. The optical filters used in 
front of each telescope segment 
were BG7 (blue/. and 
interference filters centred at 
470 . 685 and 740 nm. 
respectively. Below the four sub 
images. a processed image is 
shown, displaying the ratio of 
I(685nm)/I(blue). The excitation 
wavelength was 397 nm and the 
distance was about 40 m. The 
target diameter was about 40 cm. 
Fig. 8 is an example of a measurement performed with the imaging system on a maize plant. The 
upper part of the picture is the raw image achieved with the system. The filters used were a blue cut-off 
coloured-glass filter transmitting the broadband feature of the blue fluorescence, and three interference 
filters with peak transmission at 470. 685 and 740 nm. transmitting a narrow blue band and the two 
chlorophyll peaks, respectively. In the lower part of the picture the signal from 685 nm is divided with the 
blue broadband fluorescence signal. In this figure the laser hot spots are lost in the division, and the true 
ratio is displayed. This measurement was performed just before the field was sprayed with the herbicide 
DCMU. DCMU binds at the QB-site in Photosvstem II. hindering the electron transport from Photosvstem 
II to Photosvstem I. This results in a higher chlorophyll fluoroscence in the DCMU treated plants. This can 
be seen in Fig. 9. The upper part is exactly the same picture as the divided picture in Fig. 8 , but the scale is 
slightly different. The lower part of Fig. 9 is the same plant after treatment with DCMU shown on the 
same intensity scale. It can be seen that the chlorophyll-to-blue fluorescence ratio increased, probably due 
to the expected increase in chlorophyll fluorescence. 
4. CONCLUSIONS 
Some examples of fluorescence measurements performed on different sites in Europe have been presented. 
The measurements performed with the new detector of the spectrally resolving system show that the