## 3 Discussion  
There were a lot of differences in the morphological structure between female and male flowers and buds of the dioecious plant _H. pedunculosum_, but the difference in volatile compounds has not been reported in the literature. Buds are the state when flowers are about to bloom; their chemical components have not been lost and polluted by foreign substances, thus the research on chemical components of buds has a more realistic effect. Therefore, there were many studies which took buds as research objects, such as _Eugenia carophyllus_ (Myrtaceae) [18; 19; 20], _Capparis spinosa_ (Capparaceae) [21], _Magnolia biondii_ and _M. sirindhorniae_ (Magnoliaaceae) [22; 23], _Populus tomentosa_ (Salicaceae) [24], and _Pyrus pyrifolia_ (Rosaceae) [25]. In this study, it was found that there was significant difference in the volatile compounds between female and male buds of _H. pedunculosum_. Isoamyl alcohol is a fragrance ingredient used in cosmetics, detergents, fine fragrances, household cleaners, shampoos, toilet soaps, and other toiletries [26]. Because of its advantages of high energy density, low hygroscopicity, and compatibility with the current infrastructure, isoamyl alcohol has attracted considerable attention as one of the biofuels [27]. As a result, it was showed that the content (up to 90.19%) of isoamyl alcohol was the highest, which provided a new perspective for improving the economic value of _H. pedunculosum_. Some unique compounds in female or male buds made this study more meaningful. Two kinds of oximes and phenyl compounds were only present in male buds. For (_Z_)-3-methylbutylaldehyde oxime and (_E_)-3-methylbutylaldehyde oxime, the reports on plant volatile compounds were extremely rare: only the night-flowering plants of _Gaura drummondii_ (Onagraceae) and _Trichosanthes kirilowii_ (Cucurbitaceae) [28; 29]. For phenyl compounds, benzaldehyde was only detected in male flowers and the content of benzyl alcohol in male flowers was significantly higher than that in female flowers of _T. kirilowii_[29]. Similarly, 4-oxoisophorone was detected only in male buds in this study, which was one of nine differential compounds filtered by multivariate statistical analysis. It was shown that 4-oxoisophorone may be a key compound for honeybees' perceptions of flower odor, which was likely to be implicated in bee foraging behavior [30]. (_E_)-4-Hexenol, isoamyl acetate, and 2-ethylhexanol were only detected in female buds. It was found that the volatile compounds such as isoamyl alcohol and isoamyl acetate were more attractive to pollinators in the field behavior measurements [31]. High contents of alcohol and ester compounds were beneficial to better pollination of the female flowers of _H. pedunculosum_, which could promote the yield of fruits and improve the economic value of female plants. In addition, seven terpen were detected in female or male buds, including \(\beta\)-myrceene, \(\alpha\)-pinene, \(\alpha\)-copaene, sabinene, \(\beta\)-ocimene, \(\delta\)-limonene, and \(\gamma\)-terpinene. It was shown that terpen had the function of attracting pollinating insects, which caused the plant to attract a variety of flower visiting insects, and could promote the natural pollination of flowers [32]. There were few reports on the difference in chemical composition of dioecious plants. For example, the contents of 2-cyclohexenone and methyl benzoate in female buds were significantly higher than those in male buds, and the content of ethyl benzoate in male buds was significantly higher than that in female buds of _P. tomentosa_[23]. The content of linalool in female flowers was significantly higher than that in male flowers, whereas the content of benzyl alcohol in male flowers was significantly higher than that in female flowers of _T. kirilowii_[29]. The comparative study on the volatile compounds of the buds revealed the characteristic difference between female and male buds of _H.