Utilisation de la fluorescence des plantes en teledetection

The aim of this paper is to give an overview of the information currently available on plant canopy fluorescence and its possible use for remote sensing measurements. Two approaches are analysed and discussed: laser induced fluorescence (active remote sensing) and solar stimulated fluorescence (passive remote sensing). The active methods are based on the use of LIDAR systems. These systems are able to detect Laser-Induced-Fluorescence (LIF) at distances up to a few hundreds of meters when the signal is properly collected by telescope. Two methods are generally proposed. The first one consists of determining fluorescence ratios. The second active method for characterising the photo-synthetic activity consists in determining the fluorescence quantum yield. As its determination based on remote measurements of LIF intensities is affected by some uncontrolled parameters (chlorophyll content, instrumental characteristics...), the determination of the mean fluorescence lifetime τ seems to be a better alterntative. It has been shown that it is possible to characterise the physiologcial plant status using measurements of fluorescence lifetime. Because of the effects of the canopy structure, the classical analysis technique of time-resolved fluorescence cannot be used for the canopy response. An inversion model has been developed. Experimental results show the possibility of monitoring plant canopy status and determining the geometry of complex plant canopies. Based on time-resolved remote measurements. We present also the capabilities of the passive techniques for measuring the canopy fluorescence which could be more easily performed aboard a satellite or an airborne platform. -from English summary