Aspergillus japonicus Saito is a common soil-borne fungus, and exists on the surface of some cereal crop seeds. Secalonic acid F (SAF) is the main allelochemical from the fungus. Bioassays showed that SAF significantly stimulated the seedling growth of corn (Zea mays L.) at a concentration of 0.0375 mmol.L-1. The root length, root numbers and root oxidation activities increased by 31.7%, 13.2%, and 373%, respectively. Secalonic acid F also increased the nutrient absorption of P, K, Ca, Mg, and S at the same concentration. However, SAF inhibited the seedling growth of corn at concentrations of 0.3 mmol.L-1 and 0.6 mmol.L-1. The root length, root dry weight, and shoot length were inhibited by 27.7%, 39.1% and 35.8% by 0.3 mmol.L-1 of SAF, and root activities were inhibited by 72.1% and 100% by 0.3 mmol.L-1 and 0.6 mmol.L-1 of SAF, respectively. The nutrient absorption of N, P, K, Ca, Mg and Fe was reduced when the corn seedlings were treated with 0.3 mmol.L-1 SAF. Transmission electron microscope, observations showed that the corn treated with 0.3 mmol.L-1 of SAF had a swelling and disorderly arrangement chloroplast, and the stratiform structure of chloroplast became unconspicuous.