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- For a damaged foliage 
a) At 680nm, the reflectance is higher than that of 
the healty one and increases with the withering. 
b) with respect to the yellow band, the relative 
reflectance Rogo increases with the damages ; <n summer, when this 
factor is higher than one, it is an assured signal of necrosis. 
c) in the near infrared, R is no more a constant, but 
increases between 800nm and 900nm ; the worse is the sanitary state, 
the higher is the slope dR/dA. 
Those characteristics, emphasized on the laboratory registered 
spectrum can be found, but slightly attenuated, on the spectrum 
registered in situ (see figures). 
Remark : by measuring reflected energies in the laboratory, we 
have noticed that the reflectance of a plant in the near infrared 
part of the spectrum decreases meanwhile the damaged surface increase 
The absolute value of R on trees 4{n s{tu would certainly give a 
significant extra parameter. 
These results show that the relative spectral distributions of 
reflected energy are very significant of the sanitary State of observec 
plants. 
It appears that it is necessary to go on with this study and its 
application to the teledetection method by improving the four following 
points 
1, To reduce both the storage and calculation times of data in 
order to register a lot a spectra on a greater number of plants. 
2. To extend the spectrum towards the infrared to seek for other 
eventual necrosis significant parameters for different species. 
3. To build a spectroradiometer which can be used on board of an 
helicopter. 
4. To do in 4itu absolute energy measurements with references 
given by pyrheliometer and pyranometer. 
  
Since july 1976, we are working jointly with : 
- Institut für Physikalische Weltraumforschung 
(MM. H.J. BOEHNEL et W. FISCHER) 
- Abteilung Luftbildmessung U.- Interpretation des Institutes 
für Forsteinrichtung der Universität Freiburg. 
(Pr, G. HILDEBRANDT).