Pollen morphology ofpeumus boldus(monimiaceae) — a comparison withpalmeria scandens

Open Access
Publisher Website
Google Scholar
Abstract
Pollen of the Chilean plant Peumus boldus Molina was compared with that of the Australian plant Palmeria scandens F. Muell. (Monimiaceae) under SEM and TEM. Both have apolar, radiosymmetric, globose-spherical, inaperturate spinulose pollen of medium (Peumus) and small (Palmeria) size. The spinules appear to have been built up by successive layers of cylindrical strands of material 100–250 nm (Peumus) and 100–150 nm diameter (Palmeria). The tectum comprises interwoven cylindrical strands, smaller than those of the spinules. Ion/atom beam etching in Palmeria revealed that each strand resembled a tightly coiled spring of similar size to models for exine units proposed by J. R. Rowley and co-workers. Under TEM the spinules appeared homogeneous in section. It was concluded that this was because material cementing the strands was of similar electron density to the strands themselves. For, prolonged ion/atom beam etching of spinules revealed substructure indicating the presence of the strands. In both genera the exine is two-zoned, with an inner zone of rod-shaped, more or less radially aligned sporopolleninous elements, with, in Palmeria some innermost circumferentially aligned sporopolleninous elements too. A foot layer and endexine are absent. Both Peumus and Palmeria have a two-zoned intine with an outer zone containing tubular material. It is concluded that pollen morphology does not support the recent segregation of Peumus and Palmeria into different subfamilies.