SCABRA BUNGE
The gentiopicroside contents in different parts (94 tissue culture, 68 shoot and 68 root
samples) of G. scabra Bunge samples are shown in Table 3.1. It can be seen that the
gentiopicroside content in G. scabra Bunge whole grown plant (including shoot and root)
increased after G. scabra Bunge tissue culture was transplanted into the greenhouse for
higher in root than in shoot, indicating that during greenhouse cultivation, the
gentiopicroside was mainly stored in the root.
Table 3.1 The gentiopicroside content in tissue culture and grown plants of G. scabra
Bunge.
Sample n
Gentiopicroside Content (%)
Min. Max. Mean SD CV
Tissue Culture 94 2.69 8.18 5.35 1.29 0.24
Grown Plant
Shoot 68 1.34 5.90 3.26 0.91 0.28
Root 68 2.24 8.77 4.68 1.62 0.35
3.3.2 CORRELATION BETWEEN NIR SPECTRA AND GENTIOPICROSIDE
CONTENT
The NIR spectra of the 94 G. scabra Bunge tissue culture samples and the 136 grown
plant samples (68 shoot and 68 root) were acquired using the MSC treatment. As shown
in Fig. 3.1(A) and 3.1(B), there were absorption peaks in both visible region of blue
light (452 nm) and red light (666 nm) because the chlorophyll in G. scabra Bunge
would absorb the majority of blue and red light during photosynthesis. The spectra of
tissue culture and shoot were similar, which could be attributed to the fact that, during
the domestication period, the tissue is mainly composed of shoots, while the root
development of G. scabra Bunge is not obvious at that time. The root spectra in the
visible region showed a significant difference, with high absorption from green to
yellow light (492 to 586 nm) and low absorption (flat waveform) from orange to red
light (606 to 700 nm). This could be due to lack of chlorophyll in the roots of G. scabra
Bunge plant, which reduces absorption of blue and red light, and reflects green light.
(A) (B)
Fig. 3.1 The spectra of G. scabra Bunge powder post-MSC (A) tissue culture and (B)
grown plants.
After MSC treatment, the spectra of G. scabra Bunge tissue culture and grown plant
were analyzed using the following pretreatments: (1) smoothing; (2) smoothing with 1st
nd
the tissue culture spectra (smoothing points / gap) were (1/0), (6/6) and (8/8), whereas
the best ones of the grown plant spectra were (1/0), (2/2) and (3/3); both the smoothing
points and the gap were less than 10, indicating that NIRS 6500 spectrophotometer is
stable, and the spectra of G. scabra Bunge powder exhibits minimal noise.
The correlation between the spectra and gentiopicroside of G. scabra Bunge powder
was analyzed before selecting the specific wavelength regions. The gentiopicroside
correlation coefficient distribution of G. scabra Bunge tissue culture samples and grown
plant samples were compared using the original spectra, 1st derivative spectra, and 2nd
derivative spectra, and the threshold value (|r| > 0.55) was set to determine the degree of
correlation. It is unnecessary to avoid the O-H bond absorption band around 1450 nm
and 1900 nm because the influence of water absorption on the spectra of G. scabra
Bunge powder has been eliminated. Fig. 3.2(A) shows that the bands of high correlation
between the spectra and gentiopicroside of tissue culture were mainly distributed in the
NIR region, with only a few in the visible region. The absorption bands of the original
spectra were located in the 1st overtone of the C-H bond and C-C bond, whereas the
absorption bands of the 1st derivative spectra were located in the orange light and the
combination of the 1st overtone of C-H bond. Moreover, the absorption bands of the 2nd
derivative spectra were found to locate in the 2nd overtone of C=O bond stretch.
The correlation coefficient distributions between absorbance values of the spectra and
gentiopicroside contents of the G. scabra Bunge grown plants were also compared using
the original spectra, the 1st derivative spectra, and the 2nd derivative spectra (Fig. 3.2(B)).
It can be seen that there were highly correlated bands in both visible region and the NIR
region. The absorption bands in the original spectra were located between the yellow
and orange light, as well as the combination of two C-H bonds. The absorption bands in
the 1st derivative spectra were located between the orange and red light, the 4th overtone
of C-H bond, the 3rd overtone of C-H bond, the 1st overtone of C-H bond, and the
combination of two C-H bonds, whereas the absorption bands of the 2nd derivative
spectra were located in the blue and red light, the 3rd overtone of N-H bond, and the
combination of two C-H bonds. Because the spectra of shoot and root showed obvious
differences in the visible region, the correlation of blue and red light to gentiopicroside
was improved, indicating that the amount of chlorophyll contained in different parts of
the grown plant also affect the performance of the specific wavelength regions. The
specific wavelength regions of both tissue culture and grown plant in the NIR region
were located in the combination of two C-H bonds and the overtones of C-H bond,
indicating the C-H bonds are the main absorption of NIR. According to the absorption
bands of the C-H bonds in the spectrum, Fig. 3.2 showed that the wavelength range of
900 to 1300 nm, 1500 to 1800 nm, and 2200 to 2300 nm were the major absorption
bands, and these wavelengths can be used to provide a basis to select the appropriate
specific wavelength regions when conducting MPLSR analysis. As for the spectral band
400 to 650 nm, which belonged to the absorption band of blue to red light, color
information was also reflected in the spectra.
(A) (B)
Fig. 3.2 Correlation coefficient distributions between absorbance values of the spectra
and gentiopicroside contents of the G. scabra Bunge powder (A) tissue culture
and (B) grown plants.