## 4 Discussion  
### Spectral Signature of Hybrids  
Each sorghum hybrid evaluated by the multispectral sensor showed a distinct spectral signature. This task of differentiating genetic materials has become a promising tool in the agricultural field, especially for plant breeding, through high-throughput phenotyping. Genotype-specific spectral signatures are influenced by the anatomical, morphological and physiological characteristics of each one, and this fact can be used in breeding programs to select distinct genotypes, increasing the genetic variability required to develop superior genotypes [32; 33; 34]. Pigments such as chlorophyll, carotenoids, and anthocyanins absorb light intensely in the visible range from 400 to 700 nm. It can be seen that the reflectance of sorghum hybrids is low until near the 660 nm range (Figure 2). Ref. [35] reported that the reflectance of healthy green leaves is low in the visible range, with a slight increase at 550 nm, which corresponds to the green region. The low reflectance in the visible wavelengths is due to the greater absorption by chlorophyll, which reflects less. In the 475 nm wavelength blue region, the hybrids had little differentiation in their spectral signature. The 475 nm band, which covers the blue region, is related to the light absorption of green to yellow leaf pigments used in photosynthesis, being strongly related to the presence of xanthophylls, carotenes, and chlorophyll \(\alpha\) and \(\beta\) pigments [36; 37]. The red band (660 nm), is highly absorbed by chlorophylls to carry out photosynthesis and by phytochromes to be used in photoperiod processes. Both blue and red spectral bands are of significant importance for various plant biochemical processes, specifically photosynthesis. [PERSON] [38] states that in addition this spectrum, the Rededge and NIR bands are also necessary for photoperiod processes and tissue elongation. Figure 7: Boxplot for the F-score coefficient accuracy metric of the six machine learning algorithms used with three different inputs tested for each algorithm. Equal uppercase letters does not differ between the 5% probability model inputs by the Scott–Knott test. Equal lowercase letters does not differ between mL to 5% probability by Scott–Knott test. SB: wavelengths; VIs: vegetation indices; RL: Logistic Regression; ANN: Artificial Neural Network; SVM: Support Vector Machine; J48: decision trees J48; RF: Random Forest; DT: REPTree. Another factor that contributes to the spectral range covering the NIR and Rededge reflecting more is that biochemical light absorption is low, which varies according to leaf structure [39]. This is evident in Figure 2, where there was greater differentiation between the hybrids from the 735 nm wavelength onwards. These findings can be attributed to the different biochemical abilities and leaf structure of the hybrids and also to the fact that the 790 nm wavelength is more sensitive in differentiating between them. The sorghum hybrids behaved differently at the different wavelengths, as mentioned above. At B_475 nm (Figure 2A), hybrid H1 had the highest reflectance, followed by hybrids H3, H5, and H6, which had similar reflectance, and hybrids H2 and H4, which had the lowest and similar reflectance. Blue light in plants acts as a signaling agent and not as an energy source. This signaling is related to stomatal opening and is essential in the early hours of the day [40]. The hybrids with the lowest reflectance at this wavelength consequently absorbed blue SB, which means that these hybrids may have slightly higher photosynthetic efficiency than the others. It should be noted that the stomatal opening caused by blue light does not depend directly on the guard cell or the photosynthesis of the mesophyll in response to it, but is enhanced by red light because the action of blue light alone tends to be less effective for stomatal opening [40; 41; 42]. Hybrids H1 and H3 had the highest reflectance in SB R_660 (Figure 2C).