Comparison of optical reflectance spectrum at blade and vein parts of cabbage and kale leaves

Abstract

: Objective of the study was to compare reflectance spectrum in the blade and the vein parts of cabbage and kale leaves. A total 6 cabbage and kale leaves were taken from a plant factory in Chungnam National University, Korea. Spectra data were collected with a UV/VIS/NIR spectrometer (model: USB2000, Ocean Optics, FL, USA) in the wavelength region of 190 -1130 nm. Median filter smoothing method was selected to preprocess the obtained spectra data. We computed reflectance difference by subtraction of averaged spectrum from individual spectrum. To estimate correlation at different parts of cabbage and kale leaves, cross -correlation method was used. Differences between cabbage and kale leaves are clearly manifested in the green, red and near -infrared ranges. The percent reflectance of cabbage leaves in the NIR wavelength band was higher than that of kale leaves. Reflectance in the blade part was higher than in the vein part by 18%. Reflectance difference in the different parts of cabbage and kale leaves were clear in all of the wavelength bands. Standard deviation of reflectance difference in the vein part was greater for kale, while the value in the blade part was greater for cabbage leaves. Standard deviation of cross -correlation increased from 0.092 in the first sensor (UV/VIS) and 0.007 in the second sensor (NIR) to 0.099 and 0.015, respectively.

Determination of the sample number for optical reflectance measurement of vegetable leaf

“…2) as suggested by Ngo et al (2013), and the reflectance spectra were obtained at wavelength bands from 190 to 1130 nm in a dark condition. The spectrometer was constructed by two detector systems: a CCD detector for 190-890 nm (UV/VIS) and a CCD detector for 470-1130 nm (NIR).…”

“…Sampling location is one of the important issues for proper measurement of optical reflectance to obtain reliable and representative measurement and to save time on data collection. According to a study of Ngo et al (2013) on effects of location of sampling for Chinese cabbage and kale leaves, reflectance measurements were slightly more stable in the upper part of the blade area.…”