Assessment Of Allelopathic Potential Of Hypecoum Erectum L. And Study On Its Mechanisms

The allelopathic potential of Hypecoum erectum L.was assessed by using red pigweed, lettuce,rape,tomato and wheat as acceptor plants,which were treated by different concentrations of aqueous extracts of root or aerial parts of Hypecoum erectum L.,from the aspects of influence on germination and growth of them.The Reactive Oxygen Species(ROS) and antioxidant enzymes in lettuce,wheat,which treated by aqueous extracts of root and aerial part of Hypecoum erectum L.,IAA oxidase in lettuce treated by root and aerial part of Hypecoum erectum L.,were also investigated to look for the allelopathic mechanisms of Hypecoum erectum L.1.Tthe aqeous extracts of both root and aerial part of Hypecoum erectum L.showed inhibition on germination of red pigweed,lettuce,rape,and this inhibition has a character of concentration-dependent:the inhibition increased along with concentration increased.The inhibitory effects on red pigweed and tomato are stronger than those on lettuce and rape. Different concentrations of aqueous extracts of aerial part of Hypecoum erectum L.also showed inhibition on wheat's germination,but with a weaker effect than those on former plants.2.The aqueous extracts of both root and aerial part of Hypecoum erectum L.showed inhibition on the early growth of seedlings of red pigweed,lettuce,and rape.There were some differences between the effects on seedling's root growth and hypocotyrs growth: aqueous extracts with low concentrations displayed inhibition on all those seedling's roots' growth,and this inhibition increased with concentration's increasement.However,the hypocotyl's growth of red pigweed and rape were improved by aqueous extracts with low concentrations of Hypecoum erectum L.This may suggest that root of these seedlings are more sensitive than hypocotyls.The aqueous extracts of of aerial part of Hypecoum erectum L.showed similar influences on roots' growth and the grwoth:being improved when treated by low concentrations' extracts,while inhibited by extracts with higher concentration.3.Aqueous extracts of root of Hypecoum erectum L.showed significant influence on ROS and the activities of some antioxidant enzymes.The concentration of superoxide anion radicals in lettuce increased greatly with the concentration,which suggested that lettuce had suffered ROS intimidation,the higher the concentration,the severe the intimidation.The activities of SOD,POD,and CAT upregulated correspondingly with ROS.However, antioxidant enzymes showed some different changes when treated from the 5^th day until the 7^th day,while superoxide anion radicals continued to accumulate in lettuce.4.Aqueous extracts of aerial part of Hypecoum erectum L.also showed significant influence on ROS and the activities of antioxidant enzymes in wheat:the concentration of superoxide anion radicals in both leaf and root of wheat increased greatly with the concentration,the activities of antioxidant enzymes changed much too,but different with that in lettuce,the activities of SOD,POD,and CAT did not changed regularly with the increased concentration,and the changes in leaf were also different with that of root - root was more sensitive than leaf.The upregulation of antioxidant enzymes are probably one of the important mechanisms that lettuce and wheat react with oxidative stress brought by aqueous extracts of Hypecoum erectum L.5.The IAA oxidase in lettuce treated by both root extracts and aerial extracts of Hypecoum erectum L.did not display significant change,which suggest that IAA oxidase may not be involved directly in the inhibition on the earlygrowth of lettuce seedlings,and further research on this mechnism are still needed.To conclude,the aqueous extracts of root and aerial part of Hypecoum erectum L.have allelopathic potential from the laboratorial bioassay.Exposure to aqueous extracts made ROS accumulated in acceptor plants,and oxidative stress were caused subsequently,and the upregulation of antioxidant enzymes may be one mechanism of Hypecoum erectum L.'s allelopathy.This study provides data for both the research of biological activity of Hypecoum erectum L.and its utilization.In addition,it will be also meaningful for the biological control of weeds.