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Academic Staff


Dr Alan Hemsley

Dr Alan Hemsley obtained his first degree in botany from Bedford College, London. Following an MSc in plant taxonomy and systematics obtained at Reading, he went to study palaeobotany for his Ph.D. at Royal Holloway and Bedford New College, London. He took postdoctoral positions in Montpellier, France, and at Royal Holloway University of London before arriving in Cardiff. He currently is in receipt of a Royal Society University Research Fellowship. He lectures occasionally on topics related to Palynology, Palaeobotany and Plant Ecology.

Research interests

Alan's work aims at the elucidation of the construction and function of surface pattern and ultrastructure in the walls of living and fossil megaspores. It also addresses these aspects to a lesser extent in meiospores and pollen. The work has four principle aspects, these are ultrastructural studies, studies of morphological variation of tetrads and individual spores, modelling of environmental interactions, and the simulation of wall construction mechanisms using colloids.

Ultrastructure

Ultrastructural studies of fossil megaspores are now commonplace and much is known with regard to structural variation within and between groups. Alan's main interest now is to relate structure to developmental processes. However, continued study of various groups does provide for broader comparisons and a better understanding of variation. Three studies have been undertaken in this respect, all of which are in the final stages of preparation, the latter two having recently been given as verbal presentations at the most recent Pan-European Palaeobotanical Congress (Krakow, Poland, June 1998). Part of this work was undertaken on a grant obtained for Ms C.F. Cottnam (funded by the Nuffield Foundation NUF-URB96). These studies now provide sufficient detail of resolution within extinct lycopsid megaspores to attempt to use wall characteristics and morphology for a cladistic analysis of phylogeny which will be undertaken shortly.

Morphology

A morphological and ultrastructural examination of the enigmatic Devonian propagule Sphinxia wuhania was undertaken with J.M. Hilton and Li Cheng-Sen. This work confirmed its status as a seed-like unit.

Other studies undertaken include an ultrastructural investigation of the earliest known progymnospermic seed-megaspores from the Devonian of Greenland with Dr J. Marshall which is also in preparation.

Exceptionally preserved fossil megaspores exhibiting a number of aborted forms have made it possible to ascertain both the mode of exospore construction and the sequence of development in an extinct species (the first time this has been achieved). It is possible to be confident that these aspects differ from those of surviving, related plants, although the similarities that do occur support the existing taxonomy.

In participation with W.G. Chaloner and H.K. Goswami, Alan has been reinvestigating Isoetes pantii, a plant that is unusual in producing large, megaspore-like spores within its microsporangia, along with the very different microspores. This has permitted the question of the relationship of sporopollenin organisation in mega- and microsporangia to be investigated from both the simulated colloidal systems (see below) and within a real system. The results confirm that in this instance, processes are the same in micro- and megasporangia. This work is in preparation for publication.

Physical and mathematical modelling of behaviour

A full survey of free-sporing megaspore dispersal mechanisms through time was presented at the 'Evolution of Plant Architecture' symposium in 1995. This was described by one referee as a 'landmark publication providing the first full account' of such systems.

Enclosed seed megaspore dispersal was also investigated utilising models. These have assisted in the clarification of dispersal mechanisms of coal measure-forming plants.

Colloids

The colloidal simulation of spore wall structure has progressed from an initial success with colloidal crystal production, following the theoretical basis published in 1994.

Alan is proud to have such excellent and enthusiastic collaborators working with him on this attempt to simulate spore walls by the mechanisms used (we believe) by plants. With these colleagues, and with the apparatus now set up in Cardiff, Alan has been able to extend considerably the diversity of structure we are able to simulate, and the extend the likely applicability of our work to a much broader range on plants.

This work has been presented at the symposium giving rise to the above publication. In addition, Alan has presented these studies at the 8th International Palynological conference (Houston, Texas, July, 1996), at a Biocolloids symposium (University of East Anglia, April, 1998), and at the Pollen and Spores: Morphology and Biology symposium (Royal Botanic Gardens, Kew, July, 1998) to which a contribution has been accepted for the resulting publication.

Theory has extended further than the practical modelling and offers exciting prospects for the understanding of the role and effects of self-assembly mechanism in the development of microscopic structure, and in our concepts of the relationship of structure to genome.

Alan considers this aspect of his work to be potentially the most important. If nothing else, the production of highly realistic simulations by comparable processes to those used in plants will stimulate discussion regarding the role of self-assembly. Practical and theoretical aspects of this work provides evidence in support of micro-evolutionary change by punctuated events, and provides a possible set of circumstances by which 'hopeful monsters' might exist as a means of speciation. In addition, this work has implications in colloid chemistry since few have looked at the behaviour of mixed colloidal systems such as these. Our work is therefore pioneering in both biology and chemistry and as such has attracted attention from ICI paints and Glaxo. Alan has recently submitted a grant application with B. Vincent to extent the chemical aspects of this work.

Subsequent work in this area will concentrate on the refinement of the simulations, the production of more complex structure, and the use of more 'natural' components, of which we already have some knowledge.

In addition to these activities, Alan has also had the opportunity to introduce a new course module in Earth Sciences entitled 'Vegetation and Environment' which explores the relationship between plants, soils and underlying geology and has contributed other occasional lectures within the department.

With Dr M.H. Kurmann he continues with the editing of the symposium volume 'The Evolution of Plant Architecture' to be published this year by the Royal Botanic Gardens, Kew. He is also involved with P.R. Bell on a revision of Green Plants, their Origin and Diversity. His principal role will be to incorporate recent palaeobotanical advances into this popular and accessible text book. Earlier, he contributed the chapter on plants for a new textbook.

Alan is also acting as palaeobotanical editor for the journal Palaeontology.