Abstract: A device for analyzing plants, by luminous excitation and fluorescence measurement, can be used on site without preparation of the plants. The device evaluates the content of a compound in the skin or epidermis of a plant. The geometry of the device is characterized by a direction of the excitation light rays and a direction of the fluorescence light rays which are non-collinear with each other. The device includes several sets of emitters of different wavelengths, each including several emitters, and makes it possible to measure a plurality of excitation-fluorescence combinations. A method for evaluating and monitoring the development and maturity of a crop, as well as a method for monitoring and controlling plant treatment are also described.

Abstract: A method and device for determining the ratio of the contents of chlorophyll and of a chromophorous compound that is non-fluorescent in the band of chlorophyll fluorescence in a plant tissue, without determining the contents. The method includes: emission of two excitation radiations of chlorophyll fluorescence, one of the excitation radiations being absorbed by the chromophorous compound and the other not, measurement of the fluorescence radiations induced, the fluorescence radiation induced by the excitation radiation absorbed by the chromophorous compound being measured outside of the absorption spectrum of chlorophyll and the fluorescence radiation induced by the excitation radiation not absorbed by the chromophorous compound being measured within the absorption spectrum of chlorophyll, the ratio of the contents is determined from the ratio of the measured fluorescence radiations.

Abstract: A method and a system for jointly determining the content of a first chromophorous and fluorescent compound and a second chromophorous compound in a biological tissue (30). The determination of the content of the chromophorous and fluorescent compound (33) is carried out by optical measurement of the differential absorption of this chromophorous and fluorescent compound (33) and the determination of the content of the second chromophorous compound (34) is carried out by optical measurement of the fluorescence of the chromophorous and fluorescent compound (33). Optical radiations (11-14) are utilized which are suitably chosen in combination with at least one operation of filtering these radiations suited to using single detection (21) and measurement element for the two determinations.