Search

The Douro Basin (lower Gzhelian/lower Stephanian C, Upper Pennsylvanian; NW Portugal) is one of the richest continental sedimentary basins in fossil floras of late Carboniferous age in Portugal. Recent field work carried out in the Douro Basin allowed to report a new fossil site, of potential Lagerstätte quality, found in the Montes da Costa (Ermesinde) region. This new fossil locality preserves exceptional palaeontological, stratigraphic, lithological, and tectonic structural features of great scientific interest. An exceptional record of sudden catastrophic flooding events represents one of the most remarkable geological records documented in this new locality. In the palaeontological context, the plant assemblage described comprises a well‐preserved and very diversified macroflora of early Gzhelian age, consisting of several fossil taxa belonging mainly to genera and species of Pteridopsida, Pteridospermopsida, and Sphenopsida. Its fossil records are essentially parautochthonous deposits, but several Calamites trunks preserved in autochthonous position were documented. Within the studied plant assemblage, a new species of arborescent marattialean fern, Acitheca murphyi sp. nov., is described, and several new floral occurrences are first reported in the Portuguese Carboniferous. Here, we analyse the palaeoecological, palaeoenvironmental, and palaeoclimatic conditions of the new palaeobotanical data. Additionally, there was undertaken an extensive comparative study of Gzhelian (Stephanian C–early Autunian) age macrofloras from different localities of Europe and North America. Together with these results, a significant macrofloral biostratigraphic gap for the Kasimovian stage in the Appalachian region (West Virginia, USA) is demonstrated to be correlated to the Late Pennsylvanian of Portugal, and its palaeogeographic significance is assessed. [ABSTRACT FROM AUTHOR]

One new species of genusTranseiusis described from arborescent ferns from Brazilian Mixed Ombrophylus Forest, Rio Grande do Sul State, Brazil. These new species differ from other species by having smaller spermathecae and differences in the setaeZ4 Z5ands4as well as in the macrosetae. The male ofTranseius kroeffisGonçalves & Ferla is described and the female redescribed to account for a new hypothesis on thej-series setae. A dichotomous key for the BrazilianTranseius speciesis provided. [ABSTRACT FROM AUTHOR]

The xylem in three arborescent species of Blechnum section Lomariocycas was studied in detail using SEM, TEM, FT-IR spectroscopy and sugar composition analysis. The overall structure of root and rhizome metaxylem tracheids was similar in the three species analyzed, and characterized by mostly scalariform pitting of these multifaceted cells. Pit membrane thickness and porosity varied according to the stage of tracheid maturation. Approximately rounded deposits resembling vestures were observed in the outer pit apertures of some tracheids. Under TEM, thickenings like one-sided tori appeared on the tracheid side of tracheid-to-parenchyma contact walls; some parenchyma cells showed, in addition, features of transfer cells. As the increase in stature creates new constraints in terms of biomechanical support and water transport in plants, the characteristics found in Blechnum xylem might be related to optimization of conductive efficiency and safety. Chemical analyses of roots and rhizomes of B. yungense revealed similar levels of G-type lignin deposited in the xylem cell walls. Such lignin is the most common in ferns, including other arborescent genera. Preliminary analysis of cell wall polysaccharide composition of both root and rhizome xylem, yielded cellulose, xyloglucans and xylans with low amounts of mannans and pectins. The xylem of rhizomes had higher amounts of cellulose than root xylem. Our results are discussed in the context of functional and evolutionary aspects of xylem ferns. [ABSTRACT FROM AUTHOR]

ABSTRACT In order to successfully establish themselves in their natural environment, ferns need habitats with abiotic conditions that are suitable for spore germination and gametophyte development. The objective of this study was to assess the influence of abiotic factors on the initial development of Cyathea phalerata cultivated in vitro. Spore germination and gametophyte development were assessed under varying conditions of surface sterilization, pH, temperature and photoperiod. Exogenous contamination was eliminated by sterilizing spores with 2.5 % NaClO for 15 min and sowing them into a culture medium supplemented with nystatin. Spores germinated at all pHs tested. Gametophytic development was faster in acidic pHs. Cultures at 25 °C exhibited the highest percentages of germination and laminar gametophytes. The species produced its highest percentages of gametophytes in cultures with photoperiods between 6 and 18 h. The optimal abiotic conditions found here for in vitro development of C. phalerata are similar to those found in its natural habitat. The southern limit of this species to north of the 30th parallel in Rio Grande do Sul, Brazil, may be because further south spores do not encounter the ideal combined conditions of temperature, pH and photoperiod determined in the laboratory.