The Characteristics Of Organ And Analysis Of Volatile Components Of Michelia Crassipes

Michelia crassipes is the only garden plant with purple flowers in the genus Michelia of the Magnoliaceae.The flowers are rare in color and rich in fragrance.In order to elucidate the anatomical structure characteristics,volatile components and aroma characteristics of different flower organs in different flowering stages of Michelia crassipes Law.In this study,three kinds of floral organs,such as tepals,stamens and pistils,were used as materials in the three flowering stages(bud stage,first-open stage and fully-open stage)of M.crassipes in the sensory perception,and the paraffin section technique was used.The anatomical structure of their flower organs was studied,and their volatile components were studied by headspace solid-phase microextraction high-resolution gas chromatography-mass spectrometry(HS-SPMEGC-Orbitrap-HRMS).The main results are as follows:(1)The morphology of flower organs and the anatomical structure characteristics of cross-section at different flowering stages showed that the tepals of M.crassipes were mainly composed of upper and lower epidermis,basic parenchyma and vascular bundles.The cross-section structure of the stamen,like a butterfly,is divided into left and right halves,the middle is connected by a drug compartment,and there are 4 pollen sacs on both sides.There are pollen grains in the pollen sacs.The pistil belongs to the centrifuge pistil,with 5 carpels and 5 ventricles.The 5 ovary chambers are connected by the axial placenta,and each ovary chamber has an ovule.The number of anatomical features,oil cell density,and parenchyma cell content of floral organs increased with the change of flowering stage.The increase of epidermal cells and parenchyma of each floral organ promotes the increase of its length.Oil cells were distributed in the basic parenchyma of tepals,stamens and pistils in different periods.(2)A total of 878 kinds of volatile constituents were identified.Among them,352 kinds of tepals are in bud stage,392 kinds in first-open stage,and 434 kinds in fully-open stage;329 kinds of stamens in bud stage,383 kinds in first-open stage,and 405 kinds in fully-open stage;587 kinds of pistil in bud stage,615 kinds in first-open stage,663 kinds of fully-open stage.The types and contents of terpenoids dominated the flower organs in different periods.The pistil is the main source of volatile components in M.crassipes.(3)OAV analysis showed that the characteristic aroma components of perianth tablets at the bud stage of M.crassipes were methyl benzoate and α-pinene,which were herbal-type;The first-open stage is methyl benzoate,α-pinene and β-ionone,which are obviously herbal and floral;the fully-open stage is methyl benzoate,α-pinene,β-ionone and benzyl acetate,which are herbal,Intense sweet floral scent.The characteristic aroma components of stamens at bud stage,first-open stage and fully-open stage are ethyl 3-methylvalerate and methyl benzoate,which are fruity and herbal.The characteristic aroma components of pistil in bud stage,first-open stage and fully-open stage are ethyl 3-methylvalerate,methyl benzoate,β-damascenone,β-caryophyllene and α-pinene,which are fruity and herbal and woody.Floral and sweet aroma mainly comes from tepals,fruity aroma mainly comes from pistil and stamen,and herbal mainly comes from stamen.(4)PCA analysis and clustering heat map ’showed that pistils belonged to a single category,tepals and stamens belonged to one category.It indicated that the composition of volatile components in different flower organs of M.crassipes was quite different,but there were certain similarities.Different flowering stages of the same flower organ belong to one category,indicating that the main components of the flower organ at different flowering stages have little difference in composition,but there are certain differences in content.The floral characteristics of M.crassipes are not dominated by one or two high-content volatiles,but are interacted and influenced by a variety of volatiles,presenting a highly diverse floral fragrance.(5)Correlation analysis showed that there was a significant positive correlation between the content of volatile components in floral organs and the density of oil cells,and the density of oil cells was the key factor for the higher volatile components of pistils than tepals and stamens.