Observations of Germinating Lychnis Alba Pollen

The exine surface of Lychnis alba pollen grains is ornamented with spines and pits (Fig. 1) that are variable both in size and number. No relationship appears to exist between the relative nature of these surface features as observed by means of scanning electron microscopy (SEM) and germination potentials of the pollen. The protrusion of cytoplasm at the apertures is a common phenomenon as the grains become hydrated when placed in liquid culture medium. As swelling of the apertures occurs, the aperturate opercula, or pore plates, may be lifted to the terminal surface but frequently are displaced to one side where they become embedded in the pollen tube wall (Fig.2). Although all apertures may protrude, only a single pollen tube will normally form from each grain. The composition of the opercula appear similar to the exine in transmission electron microscopy (TEM) preparations, but is less dense than the exine when observed in SEM preparations, as indicated by surface folds suggestive of a soft composition. There is no structural evidence that enzyme degradations of the exine at germination sites is required for emergence of the pollen tube, although such may be the case when pollen germinates on the style as indicated in SEM observations of Pharbitis nil pollen.