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Since the second half of the 1980s several efforts started to establish the laser induced vegetation fluorescence as remote sensing tool to detect the growth and/or stress status of plants. The most extended European project, the EUREKA project LASFLEUR (1989 - 1994), demonstrated the technical feasibility and the significance of the sensed data. Exciting leaves with strong light pulses anywhere in the UV-A region of the electromagnetic spectrum stimulates a broad fluorescence emission from 400 to 750 nm. This emission is separated in two main components, the 'blue-green' (400 - 600 nm) and the red fluorescence region (680 - 750 nm). The blue-green band is originated by polyphenolic compounds of the cell walls, NADPH of the photosynthetic apparatus and possibly by several other plant pigments, except chlorophyll, which is the only emitter of the fluorescence at two bands in the red and in the NIR respectively. On the basis of the photon flux in these channels and with additional information, derived from e.g. the elastic back scattered signal, the time duration of back scatter and fluorescence signal, environmental light conditions, etc. a large set of vegetation parameters could be determined. During several demonstration campaigns status parameters as e.g. the chlorophyll concentration, photosynthetical activity and canopy structure were investigated. Additionally stress conditions as e.g. drought-, UV-stress and infection with different kinds of fungi were examined as well as the differentiation of plant types as e.g. mono-and dicotyledons. Extrapolating the knowledge of the EUREKA project leads to two different main applications. First with an advanced airborne remote sensing system monitoring of the vegetation status and stress conditions may be possible independently of other remote sensing techniques or the data may be used as input parameter for e.g. passive radiometer images. The second application will be a miniaturized sensor for agricultural machines giving direct access to plant parameter and hence the possibility for individual plant treatment as e.g. determining the growth state, fertilization or weed protection.
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