Effects Of Potential Allelochemicals In Amaranthus Spinosus L. On Crops Growth And Its Physiobiochemical Mechanism

The alien invasive plants have serious harm to the biological diversity and the yield and quality of crops,while allelopathy plays an active role in the process of invasion of alien plants.It is a new weapon in the competition between invasive plants and native plants.Amaranthus spinosus,endemic to America,has become a common weed of the tropics,posing harmful effects on crops,vegetables and fruit trees.In this thesis,we conducted field investigations for the distribution of A.spinosus,and explored the effect of different stress treatments on it.The effects of the aqueous extract of A.spinosus on 7 kinds of crops growth and antioxidant system and potential allelochemicals were studied.The main results were as follows:1.The survey found that A.spinosus were mainly distributed in Huzhou,Zhoushan,Quzhou,Taizhou and Hangzhou area in Zhejiang province.2.Certain adaptability of A.spinosus appeared to light drought and low-concentration salt treatment setted in the study but it was out of condition to acidity-tendency.There was a correlation between the drought treatment result and the habitat in the field investigation.3.High concentration aqueous extract of fresh A.spinosus.significantly inhibited the seed germination of rice,hot pepper,cowpea,cabbage,lettuce,cucumber,and also remarkably inhibits the seedling growth of wheat cabbage,lettuce and cucumber.The dry A.spinosus.imposed stronger effects on the 7 crops.Overall,the allelopathy of the aqueous extract of stem and leaf was stronger than that of root.The accumulation of ROS and MDA was promoted under the aqueous extract of A.spinosus,led to oxidative stress,and then affected the growth of rice seedlings.4.Using high performance liquid chromatographic analysis of the potential allelochemicals in A.spinosus.,the rutin,oleanolic acid and ?-sitosterol was found in it.The contents of them were 37.48 ?g/g,19.04 ?g/g and 144.82 ?g/g respectively.The results showed that they had inhibitory effect on lettuce,cabbageand cowpea and rice but the inhibition degree was different.The production rate of ROS and the accumulation of MDA content in rice seedlings were improved by the potential allelochemicals.The SOD,POD,CAT activity first increased and then decreased.This led to oxidative stress,which influenced the growth and development of the seedling.