Effects of gibberellic acid and chilling treatments on seed germination and seedling growth of Paeonia rockii hybrids

We explored the effects of gibberellic acid (GA3) in releasing seed hypocotyl dormancy of Paeonia rockii hybrids, and investigated the effects of root length, duration of the chilling treatment ((3±1) ℃) and GA3 concentration on the epicotyl dormancy breaking and seedling growth. Results showed that 100 mg/L GA3 treatment was the best to promote rooting. During the process of seed germination, interaction of root length and chilling treatment had a significant effect on the first sprouting time and germination rate. GA3 and chilling treatment could effectively promote the germination of seeds with radicle roots longer than 40 mm; on this basis, the chilling treatment for 14 d, combined respectively with 100, 200 mg/L GA3 or 500 mg/L GA3, was in favor of seed germination. GA3 and chilling treatment could also promote effectively the growth of seedlings with radicle roots longer than 40 mm, and the chilling treatment for 14 d, combined with 500 mg/L GA3, was optimum for seedling growth. We summarized the optimum procedure for seed germination as follows. First, the seeds should be soaked in 100 mg/L GA3 solution for 24 h and stratified in sand until roots grew up to 40 mm in length. Then they should be sowed in plug trays under the chilling treatment for 14 d. Finally, after being watered with 500 mg/L GA3 solution, they can grow up into seedlings under the greenhouse conditions.