Abstract: The characteristics of pollen tube growth and microfilament distribution of Pinus tabulaeformis were studied by in vitro culture combined with fluorescence microscopic localization. The results showed the pollen germination produced a number of grains with single tube, and also some grains with hetero-tubes, such as two tubes and ramification. Under the optimal culture condition, germination rate became stable after 60 h culture (up to 91%) and the tube length stabilized after 96 h culture (up to 173 μm). The frequency of pollen grains with hetero-tubes was significantly and positively correlated with the germination rate (r=0.786 7, P=0.004 1). The tube ramification took place at 89.73(±3.44) μm of tube elongation. Microfilament cytoskeleton distributed normally in different types of tubes and brought about the tube nucleus and amyloplasts to move toward tip of tube. In transparent zone of tube, microfilament bundles formed a dense network parallel to the direction of tube elongation. However, when the tube grew long, distribution of microfilaments tended to be thin.

Key words: Pinus tabulaeformis, in vitro, pollen tube growth, microfilament cytoskeleton