Abstract: [Objective] In order to develop genetically improved liaoning poplar (Populus×liaoningensis), the process of flowering and pollen germination were observed and analyzed.[Method] The process of flowering, pollen germination in vitro and the effect of different storage methods on pollen germination and growth of pollen tubes were investigated through water culture, pollen germination in vitro and pllen storing by means of drawing model pattern and graphic interpretation to systematically study the development of staminate catkin and pollen dispersal, and pollen germination in vitro, and to explore the impacts of different storage conditions on pollen germination and growth of pollen tubes.[Result] 1) Four stages such as bud time, extension period and so on belong to the course of the flowering. It will spent 12 days. After the anthers mature, it was easy to be dispersed for the pollen with slightly vibrate. 2) The optimal culture medium for germination was 210 g·L^-1 sucrose+30 mg·L^-1 H₃BO₃+10 mg·L^-1 CaCl₂, the rate of germination was up to 58.57%. Effects of temperature, sucrose, H₃BO₃ and CaCl₂ were remarkable in orthogonal design experiment(P≤0.05). The best culture medium for growth of pollen tubes was 150 g·L^-1 sucrose+40 mg·L^-1 H₃BO₃+10 mg·L^-1CaCl₂, the average length of tubes was 753.20 μm in seventh group. 3) The pollen tubes have no longer extended after 7 h culture in dark. 4) The germination rate was higher than any other temperatures(4℃ and room temperature) cultivating under the temperature of -20℃ and it's similar to the pollen tubes. When we laid aside the pollen in a constant temperature, as the time went on, the germination got lower and the length of the pollen tubes got shorter.[Conclusion] The pollen should be collected in the third stage to avoid the pollen loss. The relationship between pollen tubes and germination rates was no significant by statistic analysis. Pollen stored in a lower temperature had a higher viability, meanwhile, it took a shorter time for pollen tubes to reach to a same length. Compared with the fresh pollen, if the stored pollen was used to cross experiment, the times of the suitable pollination should be increased and the interval between the two fertilization should be extended.

Key words: Populus×liaoningensis, pollen, in vitro germination, storage