Minor Applications of Pollen Studies

There is no doubt that pollen studies have many applications, which can be classified into major and minor applications for the sake of convenience and proper understanding. Major applications are incorporated in Chapter 12 on Melissopalynology, Chapters 13, 14, 15, 16, 17, 18 and 19 on various aspects of Aerobiology, Chapter 20 on Forensic Palynology and Chapter 21 on use of pollen studies in exploration of fossil fuels Palaeopalynology and reconstruction of past vegetation (Palaeoecology).

In the present chapter, minor applications of pollen studies will be presented briefly under various captions such as Palynotaxonomy, Copropalynology followed by the role of palynology in environmental pollution (bio pollution).

A: PALYNOLOGY IN RELATION TO TAXONOMY

(PALYNOTAXONOMY), ECOLOGY AND EVOLUTION

Taxonomy is the scientific discipline of classification. The desire to name and classify objects, whether biological or physical, in some logical order is a basic and universal human characteristic. From time immemorial, since indeed the dawn of comprehensible language, objects which are seen and felt have been given a name. The ordering of objects into some logical order, on whatever basis, came later. Some of the earliest attempts to classify objects date back classical times - Aristotle and Lucretius were two of the earliest 'taxonomists' involved in this effort.

Taxonomy, as a scientific method, based on careful observation and logical thinking, did not develop until the 16th-17th centuries, largely due to discoveries by explorers in the wake of early empire builders. It was not until the 17th century that a significant and, to some extent, enduring system of naming individual organisms and an attempt to organize a classification scheme which reflected relationships was effected. Modification to the most important classification scheme propounded by the Swedish botanist Linnaeus, has since tried to reflect an evolutionary approach, in which naturally occurring features play a dominant role to produce a natural classification as opposed to Linnaeus' highly artificial scheme. Linnaeus based his scheme on floral structure primarily. A century earlier Anthony Van Luewenhoeck published his observations on microscopic organisms observed through his primitive microscopic lens. His published drawings included pollen. However, the nature and form of pollen was not included in Linnaeus' scheme.

To some botanists and zoologists, taxonomy is a science; to others it is an art. Whichever it is, taxonomists come in two forms 'lumpers' and 'splitters'. The former tend to recognize fewer categories or taxons (classification units), while the latter consider many more taxons are necessary to reflect adequately the organization of that which is natural to the organisms concerned. As a consequence, taxonomy is a source of much disagreement and controversy, at times bitter. Taxonomy is an ongoing activity, partly due to the constant discovery of organisms hitherto unknown to science, to add to the huge volume of specimens collected and only waiting to be named, described and classified. Natural hybridization, especially in plants renders classification a slow and often difficult process. The Irish botanist Pugsley devoted a lifetime to the study of the genus Hieracium (hawkweeds) in the Asteraceae. He was by no means a solitary figure in lifetime devotion to the study of one small group of organisms. Hybridization in hawkweeds was especially difficult to unravel due to their notorious anomalous sexual reproductive mechanisms - not always involving pollen.

As pollen are the product of living plants, which are biological systems subject to individual genetic variation, they too, are subject to variation. Over time plants evolve, undergo minute changes and occasionally major changes (mutations), which must be viable for survival. Such changes may be reflected in pollen structure, physiology and genetic composition.

Taxonomic studies of pollen is an important aspect of palynology. Pollen is classified on morphological grounds. The advent of Scanning Election Microscope (SEM) has for several decades contributed to better understanding of pollen structure and its relationship to other species. Pollen classification is of necessity tied to the classification of the plant producing it. Pollen is specific to the plant, which produces it, so the plant or species can be identified by its pollen.

In recent years several atlases of pollen grains (including also some spores, e.g. ferns) have appeared, most with keys to the morphology drawn up on a dichotomous basis. Photomicrographs of the pollen types keyed comprise the bulk of such atlases, in which pollen is usually magnified x 400. Most atlases nowadays have a section of electron micrographs taken by SEM at magnifications c. x 2,000 - 10,000.

As the taxonomy of pollen and similarly spores of selected groups of fungi, are, of necessity, related to the gross taxonomy of the organism producing them, such palynological taxonomy will, likewise, undergo change concomitant with the organism's taxonomic change or revision. However, as the role of palynological taxonomy is more or less confined to the general anatomy and morphology of the pollen grain or spore, as viewed in the surface, facilitates the identification of these structures becomes a prime object of the palynologist involved.

Once identified, the pollen grain forms the basis of much more information, such as its relationship to other similar pollen, which reflects the taxonomy of the parent; indicator of the habitat in which the parent occurred.

Pollen grains have themselves evolved with the parent plant species over time. Many palynologists research into pollen and spores of fossilized taxa. The evolutionary trends and pathways are the focus of interest in such studies. These can often be seen to have taxonomic links with more recent and present day species of pollen and spores.

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