Effects of three long-chain fatty acids present in peanut (Arachis hypogaea L.) root exudates on its own growth and the soil enzymes activities

We identified three long-chain fatty acids (Tetradecanoic, Hexadecanoic and Octadecanoic acids) in the root exudates of peanut (Arachis hypogaea L.) seedlings using a gas chromatograph coupled with a mass spectrometer and determined their relationship with peanut soil sickness. We studied their combined effects on peanut growth, production and soil enzyme activities in a simulation experiment in pot culture, using the field soil as the growth medium. Their low concentrations (80 mg kg⁻¹ soil) slightly stimulated the growth and production of peanut, but their high concentrations (160 mg kg⁻¹ soil and 240 mg kg⁻¹ soil) significantly decreased the growth and production. Chlorophyll content in peanut leaves, root activity, soil enzymes (sucrase, urease and phosphatase) activities were slightly promoted at low concentration of soil fatty acids but were suppressed at high concentrations. Decrease in photosynthates production, nutrients uptake and rhizosphere nutrients availability, probably decreased the peanut growth and production. We concluded from this study that the accumulation of three long-chain fatty acids, tetradecanoic, hexadecanoic and octadecanoic acids, in field soil has close relationship with peanut soil sickness problem. Whether they are autotoxins of peanut or not need to be further studied.