Relationship between color characteristic and reflectance index by groundbased remote sensing for flue-cured leaves and green leaves harvested

摘要

To search the critical level for optimum maturity of flue-cured tobacco leaves(KF118) on the stalk position from cutter to tips, the reflectance indexes by groundbased remote sensors as well as a measurement of chlorophyll meter were investigated for harvested leaf classified by 5 groups from light green to dark green. The sensors estimated were Crop CircleTM (Holland Scientific), GreenSeekerTM (Ntech Industries), Spectro-radiometer (LICOR, LI-1800), Chlorophyll meter(SPAD502, Minolta), and Field ScoutTM Chlorophyll meter(CM-1000, Spectrum). And L, a, b values and greenness for flue-cured leaf were measured and estimated for correlation with sensor's measurement of harvested leaf. The reflectance peaks on the wavelength of 550nm and 675nm for the reflectance curve of whole wavelength from 340nm to 1100 nm on harvested leaf were lowered as change from light green to darker green. Since the darker green leaf harvested made flue-cured leaf increase the greenness, the reflectance on the wavelength of 675nm for flue-cured leaf was decreased as to increase greenness of harvested leaf. This result means that the red edge band of 675nm wavelength was related to the absorbance of chlorophyll for photosynthesis. The greenness of flue-cured leaf showed significantly positive correlation with the entire reflectance indexes for harvested leaf while the L value by colorimeter showed negative correlation with greenness of cured leaf. Consequently the critical level for optimum maturity of harvested leaf were less than 22, 135, and 0.43 for SPAD reading, CM-1000 reading, and gNDVI by Crop CircleTM, respectively. Consequently ground-based remote sensing providing a non-destructive real-time assessment of plant greenness should be a useful tool for selection of optimum maturity of flue-cured tobacco leaves in relation to the high quality of flue-cured tobacco