Number of sampling leaves for reflectance measurement of Chinese cabbage and kale

Abstract

: Objective of this study was to investigate effects of pre-processing method and number of sampling leaves on stability of the reflectance measurement for Chinese cabbage and kale leaves. Chinese cabbage and kale were transplanted and cultivated in a plant factory. Leaf samples of the kale and cabbage were collected at 4 weeks after transplanting of the seedlings. Spectra data were collected with an UV/VIS/NIR spectrometer in the wavelength region from 190 to 1130 nm. All leaves (mature and young leaves) were measured on 9 and 12 points in the blade part in the upper area for kale and cabbage leaves, respectively. To reduce the spectral noise, the raw spectral data were preprocessed by different methods: i) moving average, ii) Savitzky-Golay filter, iii) local regression using weighted linear least squares and a 1 st degree polynomial model (lowess), iv) local regression using weighted linear least squares and a 2 nd degree polynomial model (loess), v) a robust version of 'lowess', vi) a robust version of 'loess', with 7, 11, 15 smoothing points. Effects of number of sampling leaves were investigated by reflectance difference (RD) and cross-correlation (CC) methods. Results indicated that the contribution of the spectral data collected at 4 sampling leaves were good for both of the crops for reflectance measurement that does not change stability of measurement much. Furthermore, moving average method with 11 smoothing points was believed to provide reliable pre-processed data for further analysis.

Estimation of functional components of Chinese cabbage leaves grown in a plant factory using diffuse reflectance spectroscopy

“…The diameter of the measurement probe ferrule was 6.35 mm. As reported in previous studies, the leaf spectral reflectance data were collected at 12 evenly distributed locations over the entire top surface.…”

Estimation of Glucosinolates and Anthocyanins in Kale Leaves Grown in a Plant Factory Using Spectral Reflectance

“…The spectrometer was operated by software provided by the manufacturer. Following the methodology of the previous studies of [9,37,40], the spectral reflectance data were measured from 9 sampling points over the blade part of each sampling leaf, as shown in Figure 3.…”

“…The effects of various fertilizer treatments and light intensity on functional components in white head cabbage and Chinese kale were also inspected, respectively [25,26]. A comparison was also carried out to show the similarities of wavelength ranges for estimating the functional components of kale and Chinese cabbage cultivated in plant factory and reported that leading wavelengths were found under 470~1050 nm and 317~960 nm, respectively [27].…”