The Effect Of Soil Fungus And Nutrition Stress On The Allelopathic Phenolic Acids Of American Ginseng

Phenolic acids are recognized as important defense compounds of plants. Some phenolic acids were found in the root and the rhizosphere of American ginseng. However, the role of these phenolic acids in the resistance of American ginseng on the pathogens and how the phenolic acids were influenced by the environment is not clear. In order to discuss the interaction of the phenolic acids and the pathogens, the content of phenolic adids when the American ginseng was infected by the pathogens(Fusarium oxysporum, F.solani) and the effect of phenolic acid on the growth of the two pathogens were determined. The content of phenolic acids in the root were also determined, when the American ginseng was under the nutrition stress.1. The interaction of some phenolic acids and the fungus in rhizosphere the of American ginsengFive phenolic acids, p-coumaric acid,ferulic acid, benzoic acid, salicylic acid and cinnamic acid in American ginseng were detected and measured by HPLC. The method was established.Fusarium oxysporum(C1) and Fusarium solani (F19) were chosen to inoculated the American ginseng root. The results show that:four phenolic acids,p-coumaric acid, ferulic acid, benzoic acid and cinnamic acid were detected. P-coumaric acid,ferulic acid and cinnamic acid in the root of American ginseng increased significantly after the C1infection(p<0.05). However, this phenomenon was not seen after the F19infection. The level of benzoic acid was significantly reduced after the American ginseng was infected by either F19or C1.Four Pathogens, Rhizoctonia solani(R), Cylindrocarpon destructans (B8), Fusarium oxysporum (C1), Fusarium solani (F19), and2Trichoderma (Ma3CKI-2-1and Ma3CKI-4-5) were selected in the bacteriostasis test. At the level detected in the American ginseng root,p-coumaric acid had no significant influence on the growth of the4Pathogens, but have positive effect on growth of Ma3CKI-2-1and inhibitory effect on the growth of Ma3CKI-4-5; ferulic acid had no significant influence on the growth of B8, Cl and Ma3CKI-2-1, but it can block the growth of R, F19and Ma3CKI-4-5,to some extent. Benzoic acid had no significant impact on the growth of all the6isolates.At the level detected in the soil of American ginseng, benzoic acid had no significant inhibitory effect on the growth of all the6isolates;p-coumaric acid had significant inhibitory effect on R, F19, B8, C1and Ma3CKI-4-5. P-coumaric acid showed a positive effect on growth of Ma3CKI-2-1. Ferulic acid can inhibit the growth of R, F19and Ma3CKI-4-5, and had no significant influence onthe growth of B8, C1and Ma3CKI-2-1.2. The response of phenolic acids on the lack of nitrogen, phosphorus or potassium.The lack of Nitrogen, phosphorus or potassium in the the culture solution can have some effect on the survival rate, the aboveground weight, the root weight and the total weight. The height of American ginseng can be influenced when phosphorus is absent of the nutrient solution.The lack of phosphorus and potassium can both inhibit the exhibition rate of American ginseng.The lack of Nitrogen, phosphorus or potassium can affect the content of phenolic acids in American ginseng root. For different phenolic acid, the effect was different.Both in the situation of nitrogen and potassium deficiency, the concentration of total phenolic compounds increased significantly in the exudation of American ginseng comparing with the complete nutrient solution, while decreased significantly under phosphorus deficient conditions. The contents of the3autotoxic phenolic acids decreased significantly under nitrogen, phosphorus and potassium deficient conditions. In conclusion, the contents of total phenolic compounds and the3autotoxic phenolics in the root exudation of American ginseng altered variously in the deficiency of nitrogen, phosphorus and potassium.