3.6 Combination of nano-Se and melatonin affect the VOCs of wheat seedlings under aphid infection.
As can be seen in Figure 6A, there was a significant difference among the four treatments based on the results of fingerprint similarity analysis, and collaboration of Se and MT was the greatest. For convenient comparison, the three dimensional spectrum is shown in Figure 6B. 1) The background of the spectrogram is blue, and the red vertical line at abscissa 1.0 is the RIP peak (reaction ion peak and normalized treatment).2) The vertical axis represents retention time(s) of the gas chromatograph, the abscissa represents the ion migration time.3) Each point on either side of the RIP peak represents a kind of VOC. White color means a low concentration, and red color means a high concentration. There was a difference in the types and concentrations of VOC among all samples (Figure 6C-D). Therefore, the levels of volatile compounds were estimated according to the degree of the colors.
Overall, there were 45 VOCs detected in the wheat seedlings by GC-IMS. The detailed information on the VOCs in Figure 7A was shown in Table S7. The identified VOCs included 6 alcohols, 10 ketones, 6 esters, 5 alkenes, 5 aldehydes, and 3 furans. The distributions of the molecular fingerprints in the differently treated wheat samples (nano-Se, MT, the combination of nano-Se and MT, as well as the control) were plotted in Figure 7B. The row in Figure 7B represents all the signal peaks from a specific sample, and the column represents the signal intensity of a specific VOC in different wheat samples. In addition, the numbers in the Figure represent the uncertainty of the identified substances in the migration spectrum library. The specific VOCs related to aphid resistance were plotted against the treatment of nano-Se, MT, and their combination as well as the control (Figure 7C).