Effects of seed coat, chemicals and hormones on breaking dormancy in pear rootstock seeds (Pyrus betulaefolia Bge. and Pyrus calleryana Dcne.)

Pear seeds are dormant on maturity and require pre-treatment to stimulate germination. To help find methods to increase germination percentage, we investigated seed germination responses by using several pre-treatments. The results showed that the highest germination percentage was obtained respectively after treatment of intact seeds with 0.8% H₂O₂ (hydrogen peroxide), 0.8% H₃BO₃ (boric acid), 0.6% KNO₃ (potassium nitrate) and 20% PEG-6000 (polyethylene glycol 6000) for naked seeds. For naked seeds treated by hormones, the favourable concentration of GA₃ (gibberellic acid), 6-BA (6-benzylaminopurine) and 3-IAA (indole-3-acetic acid) were 150-250 mg.l⁻¹. The overall results of these experiments showed that the treatment of seeds with chemicals and hormones in a certain concentration range could effectively increase the germination percentage of naked seeds and partially break dormancy of intact seed. Additionally, these results suggested that pear seed dormancy was controlled both by seed coat and embryo dormancy.