12. Advances in understanding the mechanisms of fluorescence emission 
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Considerable progress is observed in understanding the mechanism of laser induced fluorescence emission. Three 
significant advances were presented : 
— a new model describing the fluorescence response of algae to pulsed laser excitation, presented by 
Gorbunov and Chekalyuk (Russia). 
— a comprehensive analysis of blue-green fluorescence of leaves presented by Cerovic et al (LURE, France). 
— a time dependent canopy model enabling to separate partly the effects of changes in plant physiology and 
canopy geometry by S. Biala (Germany). 
2 - APPLICATION DOMAINS 
The recent advances provide a solid basis for the development of new approaches based on Ildars for monitoring 
crops and forest stresses. The new promising results in this field have been presented in particular by Moya et al. 
(France), Colao et al. (Ihdy) and Takahashi et al. (Japan). 
Lidar possesses also a great potential in environmental applications. A new method to quantify residue 
cover has been reported by Daughtry et al. (USA). Patsayeva (Russia) presented a paper devoted to new 
techniques for distinguishing the fluorescent response lirom oil in film (on water surface) and in dispersed form, 
as well as from dissolved organic matter. 
The review on the state of the art in the field of oceanographic lidar fluorosensors has been presented 
by Chekalyuk and Gorbunov (Russia) 
3 - FUTURE DEVELOPMENTS : 
The laser-induced fluorescence offers new possibilities for monitoring land and sea. Its advantages as compared 
to the other systems are : 
— capability for real time day and night continuous monitoring (in particular for water pollution); 
— space and time scales intermediate between satellite and ground-based measurements; 
— high spatial resolution (10 m) 
— weak dependence on weather condition; 
— recent development of operational system (Germany) to monitor the coastal zones; 
However, the main problem to solve is the development of reliable and universal algorithms for data 
interpretation. 
4 - CONCLUSION 
The research activity in the domain of laser-active remote sensing has grown quite fast in the last years. The 
mechanism of plant fluorescence are better understood and actually the remote determination of the physiological 
status of the plants can rely on three parameters : 
— the fluorescence life time 
— the fluorescence emission spectrum from blue to red; 
— the photo-induced variable fluorescence (pump an probe technique). 
In addition, the analysis of the elastically reflected signal enables a fast and accurate description of the 
architecture of a plant canopy. 
The comprehension of the laser-induced fluorescence mechanisms offers also new perspectives for the 
development of passive measurements in the Fraunhofer lines.