# Fluorescence Hyperspectral Imaging for Early Diagnosis of Heat-Stressed Ginseng Plants
## 3 Results
### ANOVA Analysis  
Band Ratio Images for the Visualization of Stressed Plants  
According to Figure 8, the highest F-values at 731 and 745 nm correspond to discrimination between the two groups of plants, with a threshold of 2.08 with 96.26% overall accuracy. The obtained results are based on the calibration data, which shows the critical wavelengths for discriminating stressed ginseng plants from the control. However, the range from 680 nm to 735 nm presented prominent bands with sharper peaks. The primary purpose of this approach was to determine the optimal thresholding value that corresponds to the detection of stressed plants based on the ratio image generated in response to the averaged intensity pixel value of the plants. Hence, the intensity pixel values for sensitive and resistant groups of samples in the stressed group were observed to be different. Therefore, it was essential to determine the optimal thresholding value in the responses of different bands combined with the range of observed changes based on conformation by the ANOVA results, which are plotted in Figure 8 and show the range between 600 and 830 nm for better visualization.  
Additionally, we combined different range bands with the suggested bands from 683 to 745 nm and calculated each band's combination performance based on correctly detecting the number of control and stressed plants (see Table 1). The higher F-value indicates more convenient discrimination relative to our targets. The computed maximum F-value is marked in Figure 8.  
Consequently, Table 1 shows the generated ratio images based on (F683.9/F731.6) bands plotted in Figures 9a-d and Figure 9e-h, providing a clear discrimination of stressed ginseng plants, respectively, that presented a high accuracy of 98% using a 1.12 threshold value. However, the results closely correlate with the exact bands suggested by ANOVA, with 96.26% accuracy. As seen in Figure 9, the image ratio visualizations based on spatial information from the surfaces of the plants showed that the sensitive groups (**a,b**) of plants were slightly more affected than the resistant (**c,d**) groups of plants. After heat treatment, the images represent the affected range, from blue to red. Specifically, the sensitive plants  
Figure 7: Reference measurements of SPAD values.  
are closer to yellow (**e,f**) than the resistant plant (**g,h**) group on the color bar east of the y-axis in Figure 9. Additionally, the changes can be observed based on the color bar on the right side of the plot on the y-axis.  
\begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline
**Total** & **Ratio** & \multirow{2}{*}{**TH**} & \multicolumn{2}{c}{**No. of**} & \multirow{2}{*}{**Sensitivity**} & \multicolumn{2}{c}{**No. of**} & \multirow{2}{*}{**Specificity**} & \multirow{2}{*}{**Accuracy**} \\
**Plants** & **WB [nm]** & & & **Correctly** & & **[\%]** & & **Detected CP** \\ \hline
160 & 683/693 & 1.13 & 66/80 & 82.5 & 80/80 & 100 & 91.25 \\
160 & 683/703 & 1.04 & 68/80 & 85 & 80/80 & 100 & 92.5 \\
160 & 683/731 & 1.12 & 78/80 & 97.5 & 80/80 & 100 & 98.75 \\
160 & 683/745 & 1.92 & 76/80 & 95 & 80/80 & 100 & 97.5 \\
160 & 731/745 & 2.08 & 74/80 & 87.5 & 80/80 & 100 & 96.26 \\ \hline \hline \end{tabular} Abbreviations stand for WB (wave band), TH (thresholding), control plants (CP), and stressed plants (SP).  
\end{table}
Table 1: Statistical analysis of two optimal wavebands for discriminating between the control and stressed plants based on the ratio image to find the optimal thresholding value.  
Figure 8: Obtained F-value of two-band ratio (731.6/745.9) by one-way ANOVA. The color scale on the right side of the contour plot presents the increase in F-values from blue to red.  
Figure 9: Resulting images visualizing the control (**top**) and heat-stressed ginseng plants (**bottom**): (**a,b**) before being subjected to heat stress; (**e,f**) after exposure to heat stress. Images in (**c,d**) show plants before exposure to heat stress, and (**g,h**) are after heat treatments.