The effects of ethylene on tension wood formation were studied in 3-year-old Fraxinus mandshurica Rupr.var.japonica Maxim.seedlings in two separate experiments.In experiment 1,ethylene evolution of buds and stems was measured using gas chromatography after 0,2,4,7,14,and 21 d of treatment;in experiment 2,both aminoethoxyvinylglycine(AVG) and AgNO3 were applied to the horizontally-placed stems,and the cell numbers on sites of applications were measured after 40 d.Ethylene evolution from buds was found to be much greater in tilted seedlings than in upright ones.The cell numbers of wood fibers in shoots and 1-year-old stems were reduced in treatments with 12.5 × 10-7 μmol/L AVG,12.5 × 10-8 μmol/L AVG,and 11.8 × 10-8 μmol/L AgNO3;whereas the horizontal and vertical diameters were reduced by treatment of 12.5 × 10-7 μmol/L AVG.Ethylene evolutions of shoots and 1-year-old stems were inhibited greatly in comparison with the control by applying 12.5 × 10-7 μmol/L AVG.The formation of a gelatinous layer of wood fibers was affected by neither AVG nor AgNO3 application.These results suggest that ethylene regulates the quantity of wood production,but does not affect G-layer formation in F.mandshurica Rupr.var.japonica Maxim.seedlings. The effects of ethylene on tension of wood formation were studied in 3-year-old Fraxinus mandshurica Rupr. Var. Japonica Maxim. Seledlings in two separate experiments. In experiment 1, ethylene evolution of buds and stems was measured using gas chromatography after 0,2 , 4, 7, 14, and 21 d of treatment; in experiment 2, both aminoethoxyvinylglycine (AVG) and AgNO3 were applied to the horizontally-placed stems, and the cell numbers on sites of applications were measured after 40 d. Ethylene evolution from buds was found to be much greater in tilted seedlings than in upright ones. The cell numbers of wood fibers in shoots and 1-year-old stems were reduced in treatments with 12.5 × 10-7 μmol / L AVG, 12.5 × 10-8 ethylene glycol monomethyl ether, μmol / L AVG, and 11.8 × 10 -8 μmol / L AgNO3; while the horizontal and vertical diameters were reduced by treatment of 12.5 × 10-7 μmol / L AVG.Ethylene evolutions of shoots and 1-year-old stems were inhibited greatly in comparison with the control by applying 12.5 × 10-7 μmol / L AVG.The formation of a gelatinous layer of wood fibers was affected by neither AVG nor AgNO3 application. These results suggest that ethylene regulates the quantity of wood production, but does not affect G-layer formation in F.mandshurica Rupr. var. japonica Maxim. seedlings.