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The first plant microfossil assemblage from the Si Ka Formation of the Song Cau Group, northern Vietnam is reported. It is composed of cryptospores in dyads and tetrads, trilete spores, tubular remains consisting of an association of smooth, banded, and externally thickened tubes, and cuticle-like fragments. The biostratigraphic assemblage of sporomorphs indicates a late Silurian (late Ludfordian) to Early Devonian (early Lochkovian) age. Further comparison with coeval reports using the characteristic features of the assemblage confines their age to the late Ludlow (late Ludfordian) to early Přidoli. This report presents the oldest spore assemblage from Vietnam and contributes to a broader understanding of its paleo-landscape during the late Silurian.

The antithetic (interpolational) hypothesis for the origin of the plant sporophyte from algal ancestors calls for the evolution of the embryophytic spore in advance of the vegetative sporophyte. Here we view the fossil record of cryptospores from lower Paleozoic strata in light of this “spores before sporophytes” paradigm. Cryptospores show marked changes between pre-Darriwilian and post-Darriwilian assemblages. These include shifts from smaller to larger spore diameters, topological changes from irregular to isometric spore-body attachment configurations, and the de novo origin of homogeneous sporoderm. These changes in spore morphology and topology appear to reflect the canalization of meiosis in the sporocyte, as karyokinesis and cytokinesis became tightly coupled and meiosis resulted in only four (meio)spores. Indirect evidence of embryophytic sporangia is first found in Darriwilian rocks in the form of homogeneous sporoderm, which is considered to be tapetal in origin. Thus, the fossil record appears to support the progressive acquisition of evolving sporophyte characters with respect to spore formation. If embryophytic sporogenesis first evolved during the Darriwilian, the antithetic hypothesis would predict that the full suite of vegetative characters that defined the first sporophyte must have evolved later. This scenario is consistent with the Homerian origin of land plants as seen in the (mega)fossil record, but it implies that the origin of lands plants, per se, was not a singularity in geologic time but rather required a long period of adaptive selection in subaerial habitats throughout the early Paleozoic.

Sporopollenin exine capsules (SECs) (outer exoskeletal wall of the spores of Lycopodium clavatum) were extracted and examined for their potential use as microcapsules. They were shown, by laser scanning confocal microscopy (LSCM), to be void of their inner contents. The removal of nitrogenous and other internal materials was supported by a combination of elemental and gravimetric analyses. Two different methods were investigated to encapsulate substances into SECs which were (i) mild passive migration of materials into the SECs and (ii) subjecting SECs and materials to a vacuum. A range of fluorescent dyes with different polarities were seen using LSCM to encapsulate efficiently into the SECs (up to 1 g.g−1). Relatively unstable materials with different polarities were encapsulated into the SECs: polyunsaturated oils, which are labile to oxidation, and the enzymes streptavidin-horseradish peroxidase (sHRP) and alkaline phosphatase (ALP). Irrespective of the encapsulation techniques employed no oxidation of the oils or denaturation of the enzymes was observed following their full recovery. This study gives the first indication of the viability of SECs to microencapsulate various potentially unstable materials without causing a detrimental effect.

Determining stratospheric ozone levels from before instrumental records began has proved difficult. Measurements of the chemical composition of plant spore walls suggest that ultraviolet-B-absorbing compounds have the potential to act as a proxy for past changes in ultraviolet-B radiation and stratospheric ozone. Stratospheric ozone screens the Earth’s surface from harmful ultraviolet-B radiation. Concentrations of stratospheric ozone are governed by a variety of natural and anthropogenic factors, including solar cycles1, volcanic aerosols2, ozone-depleting substances3 and climate change4. However, assessing this variability before instrumental records has proved difficult owing to the lack of a well-constrained proxy5. Here, we use microspectroscopy to analyse the chemical composition of herbarium samples of clubmoss (Lycophyta) spores originating from high- and low-latitude localities, where they were exposed to different ultraviolet-B histories. We show that the concentration of two ultraviolet-B-absorbing compounds in the walls of high-northern- and southern-latitude spores is strongly regulated by historical variations in ultraviolet-B radiation. Conversely, we find little change in the concentration of these compounds in spores originating from tropical Ecuador, where ultraviolet levels have remained relatively stable. Using spores from Greenland, we reconstruct past (1907–1993) changes in ozone concentration and ultraviolet-B flux; we reveal strong similarities between spore-wall reconstructions, and independent instrumental records6 and model results7. Our findings suggest that ultraviolet-B-absorbing compounds in plant spore walls have the potential to act as a proxy for past changes in terrestrial ultraviolet-B radiation and stratospheric ozone. The chemical signature of plant spore walls in herbaria, and possibly also in sedimentary and ice-core archives, may therefore prove valuable for reconstructing past variations in stratospheric ozone and their connections with changes in solar radiation and climate.

Background and aims Many key innovations were required to enable plants to colonize terrestrial habitats successfully. One of these was the acquisition of a durable spore/pollen wall capable of withstanding the harsh desiccating and UV-B-rich environment encountered on land. The spores of ‘lower’ spore-bearing plants and the pollen of ‘higher’ seed plants are homologous. In recent years, researchers have begun to investigate the molecular genetics of pollen wall development in angiosperms (including the model organism Arabidopsis thaliana). However, research into the molecular genetics of spore wall development in more basal plants has thus far been extremely limited. This review summarizes the literature on spore/pollen wall development, including the molecular genetics associated with pollen wall development in angiosperms, in a preliminary attempt to identify possible candidate genes involved in spore wall development in more basal plants.

Benefits of eicosapentaenoic acid (EPA) can be enhanced by raising their bioavailability through microencapsulation. Pollen can be emptied to form hollow shells, known as exines, and then used to encapsulate material, such as oils in a dry powder form. Six healthy volunteers ingested 4.6 g of fish oil containing 20% EPA in the form of ethyl ester first alone and then as 1:1 microencapsulated powder of exines and fish oil. Serum bioavailability of EPA was measured by area under curve (AUC(0-24)). The mean AUC(0-24) of EPA from ethyl ester with exine (M = 19.7, SD = 4.3) was significantly higher than ethyl ester without exines (M = 2, SD = 1.4, p < 0.01).The bioavailability of EPA is enhanced by encapsulation by pollen exines.

Capulisporites longiprocessum, a new species of plant spore, is described and illustrated from the Belly River formation of westcentral Alberta. A preliminary palynological study of the Belly River, Edmonton, and Paskapoo formations suggests that this spore is restricted to the Belly River formation. This conclusion is strengthened by the earlier studies of Campbell (1962), who indicated that spores of this type were confined to strata of pre-Edmonton formation age.

Microspore assemblages from the Six Inch Mine coal seam and associated shales at Quarnford, Staffordshire, northern England, were collected and studied. Three new genera, Discernisporites, Mooreisporites, and Proprisporites, and seven new species are erected and described. The maceration techniques developed for obtaining specimens from the shales in comparable condition to those from the coal seam are also described. It was found that spores belonging to the genus Florinites were dominant in the marine shales and that the variety of species in the shales was greater than that of the seam. Chaloner9s discussion gives an alternative hypothesis for the high percentage of conifer pollen in the marine shales relative to that of the coal and nonmarine shales.

Additional occurrences of Pteroretis are recorded from eleven surface and subsurface Lower Carboniferous localities. The stratigraphic range of Pteroretis is extended into the Lower Carboniferous Springer Formation, and palynological evidence is presented for a Springer age for the Jackfork Group of the frontal Ouachita Mountains of Oklahoma, rather than the generally accepted Mississippian age. An eastern Greenland presence of Pteroretis , and the associated assemblage, indicate the paleolatitudinal Grandispora suite of Sullivan (1965). Consideration is given to the affinity of Pteroretis , and it is demonstrated to be a plant spore of terrigenous origin and should not be assigned to the Dinophyceae or Acritarcha.

Sporangiies huronensis, a Devonian plant spore, has been redeposited in the present-day bottom sediments of Lake Michigan, having been eroded from an intermediate resting place in glacial till. The occurrence of the spores in certain widely distributed clay deposits as practically the only organic remains illustrates the possibility that re-deposited micro-fossils may lead investigators to an erroneous determination of the age of a deposit.