Inexpensive Method for Determining the Growth Stage of Cut Japanese Gentian Flowers from Far-red Images

概要

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Japanese gentian (Gentiana triflora var. japonica) is one of the most important floriculture crops grown in Iwate Prefecture; it is generally grown for cut flowers. Because the flowers gradually deteriorate after harvest, along with the commercial value, the growth stage of harvested flowers could be essential information for scheduling storage and transport so as to maintain the commercial value for as long as possible. However, to date, no practical technique has been developed to discriminate the growth stages. By examining the corollas of the flowers destructively by spectroradiometer, we found that the spectral radiance of older samples was lower than that of younger samples at wavelengths between 700 and 900 nm. However, for practical application of this information, an inexpensive, nondestructive technique is needed. So we attempted to distinguish the growth stage by measuring the pixel values of the corollas in far-red (720 nm) images with a new, low-cost imaging system. The pixel values decreased gradually and significantly with senescence of the flowers. Furthermore, a test of the technique's ability to discriminate younger from older samples showed fairly good performance. We discuss the suitability of the method and the cost performance of the imaging system.