CONFOCAL IMAGING OF EXINE AS A TOOL FOR GRASS-POLLEN ANALYSIS

A new method which utilises confocal optical imaging has been develope d which can be expected to improve grass pollen analysis. Confocal mic roscopy, in reflection mode, was used to examine the exine morphology of unacetolysed pollen grains from the following species of common wil d grasses: Paspalum dilatatum, Serai iu gracilis, Bromus catharticus, Dactylis glomerata, Lolium perenne, Poa pratensis, and Phalaris aquati ca. Variations in the surface texture patterns, similar to those hithe rto only seen by scanning electron microscopy, were visualised. In con trast to the latter method, specimen preparation for this confocal mic roscopy based technique was characterised by its simplicity, permittin g the use of fresh and chemically untreated pollen grains. This confoc al imaging technique, with its capacity for optical sectioning of spec imens, offered the additional advantage of allowing the examination of the sub-surface exine layers as well as thr surface morphology of the pollen grains. Furthermore, three-dimensional reconstruction of these optical sections enabled visualisation of the identified sculptural a nd structural exine elements and layers. A number of differences in th ese patterns were found, which indicate that confocal microscopy, in c ombination with image analysis, may enable finer taxonomic distinction s to be made than these currently provided by other light microscope b ased methods.