480 
From a physiological point of view thin leaves can 
be found in spring when young leaves are develop- 
ping or under stress conditions as e.g. water 
stress. In this paper we presented only the effect 
of different pigmentations. 
As mentioned before a second effect may influence 
the blue shift of the red edge, the shift of the ab 
sorption line to shorter wavelegths. This phenome 
non can be observed in the laboratory when leaves 
are treated with the herbicide DCMU, solved in 
alcoholic solution, in order to investigate e.g. the 
Kautsky effect to obtain physiological data of the 
plant. Under these special conditions, the pigment 
concentration remains constant as well as the leaf 
thickness so that the observed shift of the red edge 
may be attributed to a shift of the absorption line 
due to the influence of the solvent and the hebizide. 
It is well known that the type of solvents can chan 
ge the position of absorption lines. 
The revised version of the stochastic leaf model has 
demonstrated its usefulness in calculating reflectan 
ce spectra. 
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