Allelopathy effect of phenols in the soil from Cunninghamia lanceolata (Lamb.) Hook on the growth of Panax notoginseng

【Objective】 To reveal the reasons of unhealthy growth of Panax notoginseng root under the forest of Cunninghamia lanceolata(Lamb.) Hook, and provide a theoretical basis for soil selection in the process of planting P. notoginseng.【Method】 The soil electrical conductivity(EC), pH and phenols allelopathic substances and the growth index of P. notoginseng root(number of fibrous roots, length of main roots, fresh weight and dry weight) in unhealthy growth area were measured, and healthygrowth area treatment control. The effects of different concentrations of phenols(1, 5, 10, 15, 20, 30 mg/L) on root activity and relative conductivity of tissue extracts of P. notoginseng were studied by using filter The number of fibrous roots, length of main roots, the fresh and dry weight of root system of P. notoginseng decreased significantly in unhealthy growth soil(P<0.05, the same below). The pH value of the soil in the unhealthy growth area of P. notoginseng was significantly decreased, but the EC value was significantly increased, and the content of phenols(phydroxybenzoic acid, vanillin, syringic acid, ferulic acid and vanillic acid) wasincreased. The root growth of lettuce in unhealthy soil was significantly inhibited. Pearson correlation analysis showed that the number of fibrous roots, fresh weight and dry weight of P. notoginseng were significantly or extremely(P<0.01, the same below) positively correlated with soil pH but significantly or extremely negatively correlated with EC values. The contents of p-hydroxybenzoic acid and vanillic acid in soil were significantly negatively correlated with fresh weight and dry weight of P. notoginseng. Compared with CK, when the concentrations of syringic acid, ferulic acid, vanillic acid and the mixture were between 5 and 30 mg/L, the root activity decreased significantly. When the concentrations of vanillin, syringic acid and ferulic acid reached 15 mg/L, the relative conductivity of root solution increased significantly.【Conclusion】 The decrease of soil pH and accumulation of phenolic allelochemicals under the forest of C. lanceolata have the adverse effects on the growth of P. notoginseng.