Comparative Study On Allelopathic Effects Of Different Varieties Of Ramie

Ramie(Boehmeria nivea)is Urticaceae ramie(Boehmeria)perennial root herbaceous xerocole,is an important fiber crops and characteristic economic crop in China.Under normal circumstances,ramie root can self-renewal itself,its perennial root can grow 10 ~ 20 years.But under normal cultivation management,there would appear phenomenon of rootrotten or vacancy plant after 3-5 years continuous growth.Which could lead to ramie yield and quality decreasing,and the serious situation may cause plant death.Ramie is often affected by continuous cropping cultivation during the long years of growth and development.Researches showed that the continuous cropping cultivation is susceptible to allelopathic autotoxicity,and one reason of the allelopathic effect may be the perennial accumulation of allelochemicals in the soil.In order to clarify the influence of ramie rootrotten and its mechanism,the relationship between root-rotten and allelopathy of ramie was studied,the allelopathic effect and organic compounds of root and rhizosphere soil water extracts were analyzed.The main results were showed as follows:The bioassay about allelopathic effects of different concentrations of root and rhizosphere soil water extracts to Arabidopsis thaliana was done.The results showed that the allelopathic effects of different concentrations of root and rhizosphere soil water extracts on hypocotyl and root length of Arabidopsis thaliana showed a trend of promoted at low concentration and inhibited at high concentration.At the same concentration of root water extracts and rhizosphere soil,the inhibition to Arabidopsis thaliana by Zhongzhu 1 was more significant than that of Xiangzhu 7.The GC-MS(Gas Chromatograph-Mass Spectrometer-computer)was used to identify the compounds of the different polarity organic solvent extracts.The results showed that there were same compounds but also differences in the root and rhizosphere soil water extracts from the two ramie varieties.The allelopathic activity of the same compounds such as 2,4-Di-tert-butylphenol,Phthalic acid,butyl hex-3-yl ester,Dibutyl phthalate,Hexadecanoic acid,methyl ester,Methyl stearate have been reported many times.The arabidopsis thaliana with DR5-GUS reporter gene was used as materials,and by GUS staining,to explore the effects of the different concentration of ramie root and rhizosphere soil water extracts on the auxin distribution of arabidopsis thaliana seedlings.The results showed that the expression of auxin gene in the root tip and leaf of arabidopsis thaliana was inhibited at high concentration of the water extraction.QPCR was applied to determine the genes expression(YUCCA2?AUX1?PIN2?PIN6?TRI1?IAA3),which were related to auxin synthesis,transfer,signal transduction after the treatments of the root and rhizosphere soil water extracts.The results showed that,after the treatment of high concentration of ramie root and rhizosphere soil water extracts,the relative expression of AUX1 and TRI1 were significantly higher than that of control,and the relative expression of YUCCA2,PIN2,PIN6 and IAA3 were significantly lower than that of control.In conclusion,there was allelopathic effect in ramie,one of the allelopathy mechanisms may be that the release of allelochemicals affect the plant auxin expression,which caused plant abnormal growth,so continuous cropping obstacle and root-rotten occurred.