# Analysis of Floral Scent Component of Three Iris Species at Different Stages
## 4 Discussion  
This study investigates differences in floral scent composition among various species and developmental stages of Iris plants, specifically _Iris uniflora_, _Iris twhifolia_, and _Iris sanguinea_. PCA results indicate that the cumulative contribution rates of the first two principal components for the nine samples reach 99.13%, with only the floral scents of _Iris twhifolia_ at different stages significantly differentiated. However, due to their similar fragrances, the PCA pattern plots for _Iris uniflora_ and _Iris twhifolia_, overlapping in various flowering periods, do not show significant differentiation. With Linear Discriminant Analysis, the cumulative contribution rate reaches 86.64%, effectively distinguishing the floral scent samples at different stages of the same species. Sensor contribution analysis reveals that five sensors, namely W1W, W2W, W1S, W5S, and W2S, are most sensitive to identifying floral scents from the three Iris species at various stages, playing a significant role in differentiation. The results indicate substantial differences in floral fragrances, and the variations in floral scent components among different samples are mainly related to sulfur compounds, terpen, organic sulfur compounds, aromatic compounds, methane, nitrogen compounds, and alcohols. This conclusion provides a theoretical foundation and evidence for subsequent Gas Chromatography-Mass Spectrometry (GC-MS) analysis. The application of headspace solid-phase microextraction-gas chromatography-mass spectrometry confirms significant differences in volatile components among the three Iris species. Throughout all stages, common volatile compounds include alcohols, aromatics, aldehydes, ketones, alkanes, and esters. Among these compounds, nonyl aldehyde, capric aldehyde, 2,4-di-tert-butylphenol, and n-heptadecane are present in all samples. Cluster analysis reveals that the decay stage samples of _Iris twhifolia_ and _Iris sanguinea_ are grouped together due to their high levels of terpenes and esters. This grouping stems from the abundant presence of terpenes during the decay stages of these two Iris species. Nonyl aldehyde significantly contributes to the aroma profile of the three Iris species during all stages, owing to its high odor activity value (OAV). In the case of _Iris uniflora_, the prominent presence of 2-methyl-4-glutaraldehyde indicates its utility as an intermediate in the synthesis of the medicinal compound sleperture and an insecticide [19]. 3-hexenol, renowned for its refreshing scent, is a crucial aromatic ingredient in perfumery production worldwide [20]. Additionally, 3-hexenal, known for its strong grassy and apple-like aroma, is approved for use as a food flavoring [21]. The inclusion of \(\alpha\)-pinene not only offers inhibition against _Candida albicans_ but also serves as a raw material for soap and detergent manufacturing [22]. Many compounds with economic and medicinal value were detected in different flower samples. In the analysis of _Iris twhifolia_, notable constituents with high relative contents include 2-hexenal, which can be applied in food additives and organic synthesis intermediates [23]. Compounds such as acetaldehyde, nonanal, trans-2-hexenal, 6-methyl-5-hepten-2-one, geraniol, decanal, and heptanal are extensively employed in edible fragrance formulations [24; 25; 26; 27; 28; 29; 30], 2,4-di-tert-butylphenol is primarily used in the production of natural rubber and synthetic rubber antioxidants, plastic stabilizers, fuel stabilizers, UV absorbers, as well as intermediates in pesticides and dye production [31]. Linalool can be harnessed for basil alcohol production and is valued for its anti-inflammatory and antimicrobial properties [32]. The application of 2-pinenes encompasses the synthesis of pine oil alcohol,linalool, and some sandalwood-scented fragrances [33]. Methyl heptenone contributes to the synthesis of ionone and citral, being of great significance as a pharmaceutical intermediate [34].