Effects of different concentrations of NAA，IBA and GA3 on growth of Pinus yunnanensis var. tenuifolia seedings

The paper studied the influences of NAA，IBA and GA3 at different concentrations on seedling height，ground diameter，dry matter accumulation and root morphology of Pinus yunnanensis var. tenuifolia. The results showed that：（ 1） The seedling height growth，stem and leaf dry matter of P. yunnanensis var. tenuifolia were significantly lower than those of control treatment under different concentrations of NAA，and the root dry weight， root length，root surface area were also less than those of control treatment，but the differences were not significant. The ground diameter growth was significantly higher than that of control group when the concentration were 20 mg/ L and 30 mg/L. With the increase of NAA concentration，the root length，root surface area and root number of P. yunnanensis var. tenuifolia continuously decreased.（ 2） IBA was beneficial to the growth of seedling height and root. Stem and leaf dry matter accumulation were higher than those of control treatment when the concentration of IBA was 35 mg/L，but the effect was not significant，and seedling height growth was improved extremely significantly； root length and root tip number were extremely significantly higher than those of control treatment，the root surface area was significantly greater than that of control treatment，although the root volume was larger than that of control treatment，but the difference was not significant when the concentration was 45 mg/L.（ 3） Four concentrations of GA3 were not conducive to the seedling height growth and diameter growth of P. yunnanensis var. tenuifolia，50 mg/L GA3 had a certain role in promoting root growth，but the effect was not significant. To sum up，the promotion effect on seedling growth of P. yunnanensis var. tenuifolia was the best at 35 mg/L IBA， the growth of underground parts had a good role in promoting when the concentration was 45 mg/L，NAA was conducive to the growth of stem，GA3 promoted root growth to a certain extent. The three kinds of growth regulators can be used in different mixing proportions in the actual production to effectively solve the problem of restraining the growth of P. yunnanensis var. tenuifolia seedlings after afforestation.