It is effective to control the water stress of satsuma mandarin trees artificially in order to yield fruits with high sugar content. In the remote sensing, it is known that the water stress will cause the blue shift of the red edge wavelength in spectral reflectance of leaves.
In the present paper, the spectral reflectance measurement device with two optical systems and angular velocity sensor, which the spectrum characteristic of tree equator part can be acquired by scanning, was developed, and its basic performance was evaluated. As the result, it was confirmed that the spatial resolution was about 20mm in the diameter, and that it has the ability to catch the spectrum reflection characteristic of the measurement object excellently. Additionally, the author thought the average characteristic of the row of the spectrum characteristic that had been acquired in the scanning to be a standard value. Next, the square mean of the rest error of an individual spectrum characteristic was evaluated, and the spectrum characteristic that had come off from the standard values most was deleted one by one. The spectrum characteristic that had remained at the end was judged to be the spectrum of green leaves. And this procedure was proven to be correct as a result of processing the spectrum characteristic of the tree equator part.
And finally, the water potential and the spectrum characteristic that had been acquired using the spectral reflectance measurement device were comparing evaluated with the satsuma mandarin in the experimental field. As a result, it was confirmed that a time response to the water stress was late, and it was confirmed to be able to presume the water potential by the accuracy of SEP=0.12MPa and R
2=0.50 if the spectrum characteristic was used.
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