Abstract: We studied the pollen germination for three species of ash, Fraxinus velutina, F. sogdiana and F. americana. Response surface methodology (RSM) based on the Box-Behnken design (BBD) was used to construct a response surface model between the pollen germination rate and three ingredients of sucrose, CaCl₂ and H₃BO₃ for the culture medium. A non-constraint optimal design was adopted to obtain the optimal conditions of pollen germination for the three species on the basis of the obtained response surface model. The analysis of the model indicated that sucrose was the main influential factor for pollen germination. When the concentration of sucrose was at a certain threshold, the interaction between CaCl₂ and H₃BO₃ could be identified. The model was confirmed with pollen germination experiments corresponding to the three optimal media. The experimental results showed pollen germination rates of 58.33%, 69.71% and 59.42%, respectively. These proportions match theoretical response values well. They can also verify the effectiveness of the BBD-based response surface model and analysis technique in obtaining optimal concentrations of the culture medium components for pollen germination.

Key words: ash, Box-Behnken design, culture medium optimization, pollen germination, response surface methodology