Abstract: In vitro double fertilization in tobacco (Nicotiana tabacum L. ) was carried out and one of its significant events, the dynamics of bisexual nuclear fusion in the viable central cell, was observed by video- enhanced microscopy for the first time. The observation revealed that after in vitro fertilization the male nucleus was first fused with one of the polar nuclei, then the other. The whole fusion process could be finished within two seconds. Morphologically the fusion was very similar to common protoplast fusion mediated by polyethylene glycol. It also went through a series of processes, namely touch, adherence, membrane fusion and content mixture. The male nucleolus moved closely towards the female one but no further fusion was recorded although eventually a big nucleolus was observed in the primary endosperm nucleus. The technique for in vitro fertilization and the observation of the nuclear fusion process may enable us to peep at the mechanism of male and female gamete fusion.

Key words: Tobacco, In vitro fertilization, Central cell, Nuclear fusion