Patent ID: 8228504

Claim:
A device for determining the rate of hydration of a plant element ( 10 ) in the plant's natural environment, said device comprising: an optoelectronic probe ( 1 ) to take a measurement of an optical transmission coefficient of the plant element ( 10 ), said probe comprising i) a first light source ( 3 ) that emits light limited to a narrow-band spectrum at a first wavelength corresponding to a band of high water absorption, ii) a photoreceptor ( 5 ) having a spectral response corresponding to the first wavelength narrow-band spectrum light emitted by the first light source, the light emitted by the first light source having a mean optical power, and iii) a space between the first light source and the photoreceptor, the space sized a) for allowing placement of a plant element ( 10 ) between the first light source and the photoreceptor such that the plant element ( 10 ) is sampled in the plant's natural environment, b) so that the light emitted by the first light source passes through the plant element ( 10 ) and, after absorption by water contained in the plant element ( 10 ), the light emitted by the first light source leaves the plant element corresponding to an absorption spectral line of the water contained in the plant element, and c) to allow both the light emitted by the first light source leaving the plant element ( 10 ) corresponding to the absorption spectral line of the water and ambient light to be received by the photoreceptor; and a measuring box ( 2 ) connected to the probe, the measuring box ( 2 ) housing i) a modulator ( 6 ) arranged to modulate the mean optical power of the light emitted by the first light source ( 3 ) by modulating the first light source ( 3 ) at a determined imposed frequency and thereby creating an alternating light component illuminating the plant element ( 10 ) at the first wavelength, and ii) a synchronous detector ( 8 ) arranged for synchronous detection and rectification of the alternating light component received by the photoreceptor at the absorption spectral line of the water, the wherein relevant information relating to a hydration rate in the plant element ( 10 ) is indicated by the measured alternating light component emitted by the first light source and leaving the plant element corresponding to the absorption spectral line of the water contained in the plant element ( 10 ) and the ambient light received by the photoreceptor is eliminated from the detection.