# Analysis of Floral Scent Component of Three Iris Species at Different Stages
## 3 Results  
Figure 1 illustrates the radar map depicting the characteristic response of three Iris species at each stage. The ten sensors exhibit varying responses to the aromas of the three Iris species, generally distributed between 1 and 10. Across all samples, sensors W1W (sulphur-organic), W1S (broad-methane), W2W (sulph-chlor), and W5S (broadrange) consistently display significantly higher response values compared to other sensors. The difference between the response values of these four sensors is notable, indicating that the major classes of substances corresponding to these sensors have higher relative contents in the floral fragrance of Iris plants at all stages. During the bloom stage of _Iris uniflora_, the response values of each sensor are notably higher than those of the other eight samples. This suggests that the relative content of each type of compound in the aroma of these samples is higher compared to other stages. In the samples from various periods of _Iris twphifolia_, and the decay stage of _Iris uniflora_ and _Iris sanguinea_, the response values for each sensor detecting aroma are lower, indicating a lower concentration of aromatic compounds in these samples compared to others. In comparison with other samples, the response value of W1S replaces W5S in the top three during the decay stage of _Iris uniflora_ and the decay stage of _Iris sanguinea_. This shift indicates that the relative content of methane is higher than that of nitrogen oxides in the aroma components of the samples during these three periods, while the opposite holds for other samples. Figure 2 depicts the principal component analysis (PCA) pattern for each flowering stage of _Iris uniflora_, _Iris sanguinea_, and _Iris twphifolia_, facilitating the differentiation of floral aromas among different stages of the same Iris variety. The contribution rate of the first principal component is 97.15%, the contribution rate of the second principal component is 1.98%, and the cumulative contribution rate of the two principal components is 99.13%. This  
Figure 1: The radar map of the characteristic response of the volatile components in three Iris species at different stages. indicates that these two principal components effectively represent the main information characteristics of the samples. In Figure 2, it is evident that among the three types of Iris, only the bud stage, bloom stage, and decay stage of _Iris sanguinea_ can be significantly distinguished. In contrast, the principal component analysis pattern diagrams for each flowering stage of _Iris uniflora_ and _Iris typhifolia_ exhibit overlap, indicating that they cannot be significantly differentiated in this mode. This lack of distinction is attributed to the relatively similar odors of _Iris uniflora_ and _Iris typhifolia_ across various periods. Principal component analysis, in this context, proves insufficient for distinguishing the internal flowering stages of _Iris uniflora_ and _Iris typhifolia_. Electronic nose loading analysis is a research method employed to distinguish volatile substances in a sample using electronic nose sensors. It primarily investigates which gas substances in the sample play a key role in this distinction and determines their contribution rates. The results of electronic nose loading analysis for each stage of _Iris uniflora_, _Iris typhifolia_, and _Iris sanguinea_ are illustrated in Figure 3. The positions of sensors W1W (sulphur-organic), W2W (sulph-chlor), W1S (broad-methane), W5S (broadrange), and W2S (broad-alcohol) significantly deviate from the origin, indicating the importance of these five sensors in distinguishing the volatile components of the three Iris varieties at different stages. This observation underscores that the variations in floral composition across different periods are predominantly associated with volatile substances, such as sulphur-organic, sulph-chlor, broad-methane, broadrange, and broad-alcohol.