# Analysis of Floral Fragrance Components in Different Parts of _Iris typhifolia_
## 4 Discussion  
In this study, flag petals, pendant petals, stamens, and pistil samples of _Iris typhifolia_ in the bloom stage were used as experimental materials, and electronic nose technology together with solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) were used to explore the differences of floral components in different parts. In order to explore whether volatile substances in different parts can be significantly distinguished, this study used principal component analysis (PCA), linear discriminant analysis (LDA), and sensor differentiation contribution rate analysis (Loading) for detection. The results showed that the cumulative contribution rate of principal components 1 and 2 of the four parts reached 99.22% after principal component analysis, but, due to the similarity of the pendant petals and pistil odor, they could not be significantly distinguished by this method. By using linear discriminant analysis, the cumulative contribution rate reached 94.69%, which could completely distinguish the floral components of each part. According to the analysis of the contribution rate of sensor differentiation, it was found that W1W, W2W, W1S, W5S, and W2S were the most sensitive sensors for the recognition of flowers in different parts of _Iris typhifolia_ and played the main role in differentiation. The results showed that there were significant differences in floral odor, and the differences of floral components were mainly related to sulfur compounds, terpen, organic sulfur compounds, aromatic compounds, methane, nitrogen oxides, alcohols, and other substances. This conclusion provides the theoretical basis and evidence for the subsequent GC-MS.  
Solid-phase microextraction and gas chromatography-mass spectrometry (GC-MS) confirmed that there were significant differences in the volatile components of _Iris typhifolia_. In addition, nonylaldehyde, capric aldehyde, and 2, 4-di-tert-butylphenol were the main volatile substances in all phases. Pistil is rich in hexal, linalool, methyl heptone, d-terfendiene, and other substances. The mass fractions of 3-hexenal, trans-2-hexenal, and 2, 4-di-tert-butylphenol were higher in flag petals and pendant petals. Stamens contain 2, 4-di-tert-butylphenol, hexal, methylheptone, and other substances. These high-content volatile substances provide ideas and reference for extraction, utilization, and development. In this study, the volatile substances detected in various parts of _Iris typhifolia_ are mostly aldehyde, aromaticity, terpene, alcohol, and alkane. In cluster analysis, the pistils are grouped together with the other three parts only in the third-tier classification, due to their higher content of terpen. By calculating the Odor Activity Value (OAV), it is found that the two substances with the highest OAV values are contained in the pistils, indicating that the pistils are the primary contributor to the aroma components and aroma profile of _Iris typhifolia_. In this study, the following compounds with higher mass fractions are detected in various parts of _Iris typhifolia_ during the bloom stage. 3-hexenal is commonly used as a flavor because of its strong grass and apple aroma [24]; 2-hexenal can be utilized in creating flavors of apple, strawberry, berry, and other fruits [22]. Chlorophylll aldehyde has a fresh green leaf fragrance, which can be used in artificial flowers, essential oils, and various kinds of floral fragrances [25]. Linalool is used in fragrances, deodorants, anti-caries, and insecticides [26]; 2-pinene can serve as a solvent for paints and varnishes and as a raw material for synthetic fragrances [27]. (+)-Dipentene and methylheptone are allowed to be used as edible flavors, mainly for the preparation of flavors [28; 29]. 2, 4-di-tert-butylphenol can be used as antioxidant, stabilizer, and ultraviolet absorber intermediate [30]; nonylaldehyde is widely used in flavor formulations, and it can also be used as a food flavor [31].