Soft and sticky development: some underlying reasons for microarchitectural pattern convergence

Surface sculpture of spores, pollen and other walled microscopic organisms commonly resembles patterns seen elsewhere in nature. These patterns are often species specific and of significant use in taxonomic study, particularly so in the fossil record where other data may be minimal. It can be argued that patterning, which must be governed to some extent by genotype, could simply reflect other natural patterns as a result of physical and chemical interaction during development. But does this diminish the view that patterning can often perform important biological functions? With examples drawn from fossil and living walled structures, we analyse the complex relationship between genetic constraints, construction mechanism and biological function, and we conclude that similar function may often result in similar pattern, perhaps further enhanced by similar aspects of development. The genetic complement, by way of selection, 'learns' to repeat the pattern, but each pattern creation mechanism retains a 'personal signature' reflecting its evolutionary history. With this new perspective in mind, we assess the potential implications in the study of Palaeozoic microfossils when many different groups are first developing surface patterning

Paleozoic megaspores

Review of knowledge of Palaeozoic megaspores, with list of taxa and comprehensive bibliography

The spores of the Dinantian lycopsid cone Flemingites scottii from Pettycur, Fife, Scotland

Cones belonging to arborescent lycopsids occur abundantly in the Pettycur Limestone facies of the Asbian (late Dinantian, Carboniferous) at Pettycur, Fife. The most abundant cones are heterosporous and have been described by Wiliamson, Scott and others under the name Lepidostrobus veltheimianus Sternberg. Jongmans subsequently named these cones L. scotii Jongmans and the species was later transferred to the cone genus Flemingites. The type specimens (which are in a thin section) are cones which contain both megaspores and microspores. The megaspores can be identified in section as Lagenicula subpilosa (Ibrahim) f. major Dijkstra ex Chaloner and have been figured by numerous authors. The microspores which occur in sporangia at the tip of the cone belong to the genus Lycospora. A new species L. chaloneri is here erected for these spores. Spores have been extracted from new specimens of cones and studied using light and scanning electron microscopy, and their ultrastructure investigated using transmission electron microscopy. Under TEM the exine of Lagenicula consists of a solid basal lamina with an inner exine composed of small globular units which become larger and interlnked in the outer exine. The microspores are small (20 micrometer) subtriangular with a distinctive distal ornament of small (1-2 micrometer) conate-echinate spines. They have a two-layered wall

Carbon-13 solid state nuclear magnetic resonance of sporopollenins from modern and fossil plants

13C solid-state nuclear magnetic resonance (NMR) has been applied to modern pollen and spore exines (Betula, Pinus and Lycopodium) and those of two fossil spores (Lagenicula and Parka) in order to assess the composition of their constituent sporopollenin. While they prove to have broadly similar structural characteristics, there are some significant differences between all types and and particularly between the fossil and living material. The capacity of NMR to to demonstrate variation in structure, in what is clearly a heterogeneous group of organic macromolecules, suggests the possibility that this procedure could be of use in characterizing the sporopollenin of different plant groups. The fact that such material retains its structural integrity in the fossil state further opens up the possibility of our following evolutionary changes through time of this inert biomacromolecules

Decomposition in soil and chemical characteristics of pollen

The input to soils made by pollen and its subsequent mineralization has rarely been investigated from a soil microbiological point of view even though the small but significant quantities of C and N in pollen may make an important contribution to nutrient cycling. The relative resistance to decomposition of pollen exines (outer layers) has led to much of the focus of pollen in soil being on its preservation for archaeological and palaeo-ecological purposes. We have examined aspects of the chemical composition and decomposition of pollen from birch (Betula alba) and maize (Zea mays) in soil. The relatively large N contents, small C-to-N ratios and large water-soluble contents of pollen from both species indicated that they would be readily mineralized in soil. When added to soil and incubated at 16 degrees C an amount of C equivalent to 22-26% of the added pollen C was lost as CO2 within 22 days, with the Z. mays pollen decomposing faster. For B. alba pollen, the water-soluble fraction decomposed faster than the whole pollen and the insoluble fraction decomposed more slowly over 22 days. By contrast, there were no significant differences in the decomposition rates of the different fractions from Z. mays pollen. Solid-state C-13 nuclear magnetic resonance (NMR) revealed no gross chemical differences between the pollen of these two species, with strong resonances in the alkyl- and methyl-C region (0-45 p.p.m.) indicative of aliphatic compounds, the O-alkyl-C (60-90 p.p.m.) and the acetal- and ketal-C region (90-110 p.p.m.) indicative of polysaccharides, and the carbonyl-C region indicative of peptides and carboxylic acids. In addition, both pollens gave a small but distinct resonance at 55 p.p.m. attributed to N-alkyl-C. The resonances attributed to polysaccharides were lost completely or substantially reduced after decomposition