Fern Sporangia Research Articles

Taxonomic revision of conodonts of Piauí formation, Parnaíba basin, updating to late Bashkirian age and biostratigraphic – Paleoecologic correlation with the Itaituba formation, Amazonas basin

This study analyzed conodont elements retrieved from Mocambo Carbonates, marine portion of the Piauí Formation, Parnaíba Basin, Northeast Brazil, West Gondwana. This manuscript aims i) to update the conodont fauna and, ii) to refine the biostratigraphic and paleoecological data of the marine portion, according to new conodont occurrences. The description of the conodont species Diplognathodus orphanus, Idiognathodus incurvus and Adetognathus lautus, suggests a late Bashkirian age. In addition, the presence of adults and juvenile Diplognathodus orphanus and Idiognathodus incurvus, as well as fern sporangia, ostracods, benthic foraminifers, and fish teeth, indicate a very shallow marine platform, of neritic tidal facies. The Mocambo Carbonates are traditionally recognized as Pennsylvanian in age, and thus, with our conodont contribution is refined to late Bashkirian. Paleoecologically, this sequence is interpreted as very shallow marine facies. We also correlate the marine carbonate sequence of the Piauí Formation, Parnaíba Basin, with the marine shallow waters from the Itaituba Formation, Amazonas Basin. This is well-positioned with international biozones from North America, China and Europe, allowing the correlation of the Piauí marine portion with the transgressive-regressive epicontinental Itaituba-Piauí Sea in Northwest South America, Western Gondwana, during the Late Paleozoic.

Challenging the paradigms of leaf evolution: Class III HD-Zips in ferns and lycophytes.

Despite the extraordinary significance leaves have for life on Earth, their origin and development remain vigorously debated. More than a century of paleobotanical, morphological, and phylogenetic research has still not resolved fundamental questions about leaves. Developmental genetic data are sparse in ferns, and comparative studies of lycophytes and seed plants have reached opposing conclusions on the conservation of a leaf developmental program. We performed phylogenetic and expression analyses of a leaf developmental regulator (Class III HD-Zip genes; C3HDZs) spanning lycophytes and ferns. We show that a duplication and neofunctionalization of C3HDZs probably occurred in the ancestor of euphyllophytes, and that there is a common leaf developmental mechanism conserved between ferns and seed plants. We show C3HDZ expression in lycophyte and fern sporangia and show that C3HDZs have conserved expression patterns during initiation of lateral primordia (leaves or sporangia). This expression is maintained throughout sporangium development in lycophytes and ferns and indicates an ancestral role of C3HDZs in sporangium development. We hypothesize that there is a deep homology of all leaves and that a sporangium-specific developmental program was coopted independently for the development of lycophyte and euphyllophyte leaves. This provides molecular genetic support for a paradigm shift in theories of lycophyte leaf evolution.

Animal–plant interactions in a Middle Permian permineralised peat of the Bainmedart Coal Measures, Prince Charles Mountains, Antarctica

Evidence for invertebrate feeding on glossopterid gymnosperms is documented from Middle Permian silicified peats of the Prince Charles Mountains, Antarctica, in the form of coprolites occurring both free in the peat matrix and clustered within excavations in roots, aerial wood and leaves. Observations of coprolites in thin-sections of the peats and from scanning electron microscopy of examples extracted via bulk maceration reveal nine morphotypes distinguished by size, shape, surface texture and contents. These include coprolites with coarse plant debris, spirally ornamented coprolites, coprolites containing spore/pollen remains and fern sporangia, coprolites within Glossopteris leaves, an ellipsoidal morphotype within a fern sporangium, large isolated coprolites between matted leaves, clustered forms filling galleries inside Vertebraria roots and Australoxylon wood, forms with coarse indeterminate constituents and others with fungal contents. Other faunal evidence is limited to indeterminate arthropod exoskeleton fragments. Collectively, the coprolites within the permineralised peat from the Prince Charles Mountains document the presence of diverse feeding behaviours including stem feeding, sporangial feeding, palynivory, root feeding and mycophagy. The first evidence of invertebrate feeding traces in Vertebraria (glossopterid) roots is identified. These findings indicate that herbivory by invertebrates in the high-latitude Permian forest-mire ecosystems of Antarctica was more intense and diverse than previous studies have reported, and affected all parts of the Glossopteris plant, together with components of associated herbaceous taxa.

Transpiration actuation: the design, fabrication and characterization of biomimetic microactuators driven by the surface tension of water

We have designed, fabricated and characterized large displacement distributed-force polymer actuators driven only by the surface tension of water. The devices were inspired by the hygroscopic spore dispersal mechanism in fern sporangia. Microdevices were fabricated through a single mask process using a commercial photo-patternable silicone polymer to mimic the mechanical characteristics of plant cellulose. An analytical model for predicting the microactuator behavior was developed using the principle of virtual work, and a variety of designs were simulated and compared to the empirical data. Fabricated devices experienced tip deflections of more than 3.5 mm and angular rotations of more than 330° due to the surface tension of water. The devices generated forces per unit length of 5.75 mN m−1 to 67.75 mN m−1. We show initial results indicating that the transient water-driven deflections can be manipulated to generate devices that self-assemble into stable configurations. Our model shows that devices should scale well into the submicron regime. Lastly, the actuation mechanism presented may provide a robust method for embedding geometry-programmable and environment-scavenged force generation into common materials.

Aspects of the morphology and ecology of two Panamanian ant-plants,Hoffmannia vesciculifera(Rubiaceae) andBesleria formicaria(Gesneriaceae)

ABSTRACTTwo formicarial ant-plants endemic to Panama and adjacent areas of Costa Rica co-occur in mid-elevation cloud forest yet have distinctive modifications to house and feed small, retiring ants.Besleria formicaria(Gesneriaceae) hosts onlyPheidolesp. which harvest the oil-rich seeds of its host and other plants and insect parts.Hoffmannia vesciculifera(Rubiaceae) hosts onlySolenopsissp. ants which obtain lipid and possibly other nutrients from vescicular tissues. Judging by their abundance in refuse deposits, fern sporangia appear to be a plentiful and evenly distributed resource exploited by both ant species.

Diet of the Hastings River mouse (Pseudomys oralis)

The diet of the Hastings River mouse (Pseudomys oralis) has been assessed from 90 faecal samples collected from 42 animals in nine different locations in New South Wales. Repeated sampling of individuals over periods of 4-6 days gave consistent results confirming the reliability of the dietary estimation techniques used in this study. No differences were found between males and females when tested at two different sites. Eight dietary items were identified with the mean percentage occurrences for summer and winter, respectively, being: leaf, 45, 77; seed, 44, 12; insect, 7, 2; stem, <l , 7; flower, 2, <l ; pollen, 1, <1; fern sporangia, <1, 1; and fungi, <l , 1. A two-way ANOVA of geographical locality and season (summer v. winter) showed no locality effect, but a strongly significant season effect for leaf (P <0.0001), seed (P <0.0001) and insect (P < 0.007). A similar multivariate two-way ANOVA for overall diet also showed a significant season effect, but no locality effect. The summer co-dominance of leaf and seed shifted to almost complete dominance of the winter diet by leaf material. This differs from the trends in dietary composition of all other species of Pseudomys studied, which broaden their diet in winter to incorporate many different types of food. It is not clear whether this reflects an active choice by P. oralis to select for increased amounts of leaf, or a default selection caused by the lack of alternative dietary items, such as fungi, which are utilised in winter by the other species.

Palaeofloristic assemblages and palaeoecology of the Lower Oligocene Bembridge Marls, Hamstead Ledge, Isle of Wight

A sequence of nine, plant-macrofossil-bearing horizons has been recognized in the Lower Oligocene from the Isle of Wight, England. The plant fossils are contained in finely laminated, olive-brown to black silty-clays and clays. Some horizons exhibit rhythmic alternation of sediment couplets; others show evidence of bioturbation and rootlet penetration. These horizons are included within a sequence of finely laminated greenish grey silty-clays and clays, largely devoid of plant macrofossil material. The plant-bearing horizons contain abundant fruits, seeds, fern sporangia, Azolla megaspores, and rare leaves. The nearest living relatives of the fossils all inhabit an aquatic or marginal aquatic environment. The associated fossil fauna includes lake bottom and lake margin species. The palynoflora of the plant-bearing and immediately underlying horizons includes large numbers of planktonic algae and limited representatives of a forest vegetation. It shows a strong relationship between the occurrences of Sparganiaceaepollenites pollen and of Typha macrofossils. Palaeoecological interpretations of this plant-fossil-bearing sequence are discussed with particular reference to modern environments. One new genus and three new species are described. Emendations are presented for four other species. Stratiotes leaf margin teeth are described.

The conduction of sap

An apparatus has been constructed for the detection of vibrations generated within plant tissue. This can detect vibrations due to water cavitation within fern sporangia. Using this detector 'clicks' have been obtained from Ricinus petioles and leaves in a condition when, from previous work, water cavitation might be expected.Evidence is provided to show: 1. That 'click' production is correlated with the water status of the plant tissue. 2. There are reasons for opposing the possibility that 'clicks' result from tissue fracture alone. 3. The 'clicks' may be detected in a wide range of plants. The implications of the apparent vulnerability of water conducting systems in plants are discussed.

Meiosis and Sporogenesis in Excised Fern Leaves Grown in Sterile Culture

When pinnae bearing sporangia at the premeiotic spore-mother-cell stage of development were excised from sporophylls of dormant plants of Osmunda cinnamomea and grown in sterile culture on media containing sucrose and inorganic salts only, meiosis was initiated in the spore mother cells, and haploid spores were produced. The spores lacked an exine but were viable, germinating to produce apparently normal prothalli which bore sex organs and on which sporophytes arose. Supplementing the culture medium in various ways altered the proportion of sporangia in which meiosis was initiated and the state of the contents when development terminated. The results are interpreted as supporting the view that meiosis requires a stimulus which arises in the vegetative shoot of the plant. There are marked differences in the behavior of fern sporangia and angiosperm anthers excised at a premeiotic stage of development and grown in culture