| During the long-term adaptation and natural succession in the environment of the plant communities, one kind of plant affected growth and development of other plants nearby through excreting secondary metabolite, besides competitions on the ground and the underground space among individuals. Biochemical allelopathy among plants was the dominant cause of regional distribution of plants, which affected form, distribution and succession of plant communities and influenced growth and development, physiology and metabolism of individual at the same time. This paper summarized the research methods of allelopathy, the releasing mode of allelochemicals, the types of allelochemicals and its application in agricultural production, at first. Then, the purpose and the significance of this research was analysed, according to the growth advantage of H. scandens in natural environment.Humulus scandens (Lour.) Merr was an annual or perennial herb of Cannaboideae (Moraceae). It was usually fascicular and had strong scramble and vitality. This plant had flourishing leaves and well developed root system in natural ecological environment, showing superiority or a single community. The research of its allelopathic potential and isolation and identification of its allelochemicals would provide theoretical basis for rational utilization of Humulus wild plant resources and development of new natural pollution-free herbicide.By the release approach of the allelopathic compounds, the allelopathy of the H. scandens was studied in this paper. Wheat (Triticum aestivum), lettuce (Lactuca sativa), radish (Raphanus sativus) and pepper (Capsicum annuum) were used as four tested crops. Volatile substances from stem and leaf, root exudates and the aqueous leachates of rhizosphere soil of H. scandens were conducted to study according to the releasing routes of plant allelochemicals in nature conditions. And the allelopathic effects of the extracts were testwd on the seed germination and growth of the receptor plants in lab. Subsequently, potential allelochemicials of volatiles, root and rhizosphere soil exudates were analyzed by GC-MS. The results encouraged the use of these allelopathic compounds from H. scandens as models for development of new herbicides, reasonably and effective use resources. The main results showed as follows:1. The allelopathic potential of volatiles from H. scandens were studied on four crops were bioassayed in lab. The experimental results indicated that: (1) Volatiles released from fresh leaves and stems of H. scandens in an airproof system significantly inhibited the seedling growth of wheat, lettuce, radish and pepper (p<0.01). (2) For further study, volatiles extracted from air dry leaves and bulbs of H. scandens by petroleum ether significantly inhibited the seedling growth of the four tested plants in an airproof system (p<0.01). (3) Extracts of air dry H. scandens under treatments of 2, 5, 10, 20, 40, 100, 200mg/mL (concentration of dry weight) were applied to test their effects on early development and seed germination of wheat, lettuce, radish and pepper. The seeding growth and germination of tested plants increased at a lower concentration but decreased at a higher concentration. And inhibition was strengthened along with the increase of extracts'concentration. Then use gas chromatograph-mass spectrometer to identify its allelochemicals. Chemical analysis (GC- MS) yielded a total of 26 organic compounds, including fatty acids, steroid, volatile oil, terpene and its oxygenated compounds that had been confirmed to be bioactive substances.2. This paper studied the allelopathic potential of H. scandens root exduates and rhizosphere soil extract, and identified its chemical substances by GC-MS. The results showed: Among six concentrations of H. scandens root extracts, 2 mg/ml extracts had slightly promoted effects on the growth of radicle and seedlings of some tested plants. 200 mg/ml extracts had significantly inhibited effects on seed germination and growth of lettuce, wheat, radish and cucumber. And inhibition was strengthened with the increase of extracts'concentration. Petroleum ether extracts from freeze-dried root aqueous were considered to be 30 chemical components, mainly including phenol, ester, alkane and fatty acids indentified by GC-MS.3. Compared to wasteland soil in the same area as the control, extracts collected from fibrous roots soil (T1), main roots soil (T2), surface soil (T3) and deep soil (T4) of H. scandens significantly inhibited the seeds growth of tested plants(p<0.05). The lever of germination rate, root length and shoot length inhibition was T1>T2>T3>T4 from strong to weak in the order. Inhibition on each parameter of shake-off soil liquid extract was over 50%, which showed strong allelopathic activity. Petroleum ether extracts from freeze-dried fibrous roots aqueous were considered to be 36 chemical components, mainly including phenol, ester, alkane and fatty acids indentified by GC-MS. |
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