Scanning Electron Microscopy of Motile Male Gametes of Land Plants.

The only motile cells produced in land plants are male gametes (spermatozoids), which are reduced to non-flagellated cells in flowering plants and most gymnosperms. Although a coiled architecture is universal, the complexity of land plant flagellated cells varies from biflagellated in bryophytes to thousands of flagella per gametes in the seed plants Ginkgo and cycads. This wide diversity in number of flagella is associated with vast differences in cell size and shape. Scanning electron microscopy (SEM) has played an important role in characterizing the external form, including cell shape and arrangement of flagella, across the varied motile gametes of land plants. Because of the size and scarcity of released swimming sperm, it is difficult to concentrate them and prepare them for observation in the SEM. Here we detail an SEM preparation technique that yields good preservation of sperms cells across plant groups.