Thalloid Liverworts Research Articles

Membrane integrity, oxidative damage and chlorophyll fluorescence during dehydration of the thalloid liverwort Monoclea forsteri Hook.

Monoclea forsteri Hook. is a thalloid liverwort species that is found in damp habitats and can, therefore, be expected to be sensitive to dehydration. It does, however, have some unique chemical constituents and anatomical features that could play a role in dealing with the adverse effects of water deficits. Corresponding to the habitat, M. forsteri lost its turgor at high relative water content (RWC≈0.90) and did not survive drying below 20% RWC. Moreover, the gametophytes showed an increase in malondialdehyde content and a depletion of the ascorbate pool during dehydration, indicating oxidative damage. Cellular constituents did not affect turgor pressure during drying and electrolyte leakage from the cells was greatly increased at RWC<0.20. Photosynthetic processes seemed not to be affected by the loss of turgor, but a decline appeared to correlate with an increase in electrolyte leakage. A speedy and fully sustained recovery from dehydration was realized from water contents above 30% and seemed only to be possible if membrane integrity could be preserved. Anatomical characteristics within M. forsteri gametophytes deserve further investigation to better understand their physiological functions.

γ‐Tubulin and microtubule organization during meiosis in the liverwort Ricciocarpus natans (Ricciaceae)

Extant liverworts are "living fossils" considered sister to all other plants and as such provide clues to the evolution of the microtubule organizing center (MTOC) in anastral cells. This report is the first on microtubule arrays and their γ-tubulin-nucleating sites during meiosis in a member of the Ricciales, a specialized, species-rich group of complex thalloid (marchantioid) liverworts. In meiotic prophase, γ-tubulin becomes concentrated at several sites adjacent to the nuclear envelope. Microtubules organized at these foci give rise to a multipolar prometaphase spindle. By metaphase I, the spindle has matured into a bipolar structure with truncated poles. In both first and second meiosis, γ-tubulin forms box-like caps at the spindle poles. γ-Tubulin moves from spindle poles to the proximal surfaces of telophase chromosomes where interzonal microtubules are nucleated. Although a phragmoplast is organized, no cell plate is deposited, and second division occurs simultaneously in the undivided sporocyte. γ-Tubulin surrounds each of the tetrad nuclei, and phragmoplasts initiated between both sister and nonsister nuclei direct simultaneous cytokinesis. The overall pattern of meiosis (unlobed polyplastidic sporocytes, nuclear envelope MTOC, multipolar spindle origin, spindles with box-like poles, and simultaneous cytokinesis) more closely resembles that of Conocephalum than other marchantiod liverworts.

Genetic diversity in cyanobacterial symbionts of thalloid bryophytes

Two species of thalloid liverworts, Blasia pusilla and Cavicularia densa, form stable symbioses with nitrogen-fixing cyanobacteria. Both bryophytes promote the persistence of their cyanobacterial associations by producing specialized gemmae, which facilitate the simultaneous dispersal of the host and its nitrogen-fixing symbionts. Here the genetic diversity of cyanobacterial symbionts of Blasia and Cavicularia is examined. The results indicate that the primary symbionts of both bryophytes are closely related and belong to a specific group of symbiotic Nostoc strains. Related strains have previously been reported from hornworts and cycads, and from many terricolous cyanolichens. The evolutionary origins of all these symbioses may trace back to pre-Permian times. While the laboratory strain Nostoc punctiforme PCC 73102 has been widely used in experimental studies of bryophyte-Nostoc associations, sequence-identical cyanobionts have not yet been identified from thalloid liverworts in the field.

Origin and relationships of the myco-heterotrophic liverwort Cryptothallus mirabilis Malmb. (Metzgeriales, Marchantiophyta)

Heterotrophic life histories have evolved independently numerous times in the angiosperms. In non-vascular embryophytes, heterotrophy is known only in the genus Cryptothallus. Cryptothallus mirabilis obtains photosynthates indirectly from a host tree via a basidiomycete that is simultaneously ectomycorrhizal on the host, a strategy known as myco-heterotrophism. This simple thalloid liverwort was initially described as an albino variant of Aneura pinguis, and the literature varies on whether it should be considered as such, as a distinct species of Aneura, or as a separate genus. Here, the relationships of C. mirabilis within the family Aneuraceae are reconstructed using DNA sequence data from the chloroplast (rps4, rps14, atpB-rbcL spacer, trnG), mitochondrial (trnS), and nuclear (26S and ITS) genomes. Several allopatric populations of C. mirabilis and of both sympatric species of Aneura (i.e. A. pinguis and A. maxima) were included. Cryptothallus mirabilis is resolved as having a single origin from within Aneura, and hence the myco-heterotrophic liverwort should be considered as a distinct species of Aneura, rather than an autonomous genus. The fungal symbiont of the photosynthetic A. pinguis is of the same genus, Tulasnella, as that of C. mirabilis, suggesting that the heterotrophic life strategy might have evolved from a pre-existing symbiosis. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 156, 1–12.

Cryptic speciation in liverworts – a case study in the Aneura pinguis complex

Bryophytes are amongst the most ancestral terrestrial plants and often have large distribution ranges across continents. Recent biochemical and molecular studies have suggested that many worldwide morphological species of bryophyte may represent genetically divergent and reproductively isolated cryptic species. We tested the cryptic species hypothesis in the thalloid liverwort Aneura pinguis complex. We applied analyses of chloroplast DNA (cpDNA) sequence variation and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methods to discriminate between specimens of A. pinguis derived from various habitats in five distant geographical regions in Poland. Of the 19 specimens sequence characterized for the cpDNA tRNALeu region, seven haplotypes were identified divided into three nonmonophyletic clusters. The application of developed PCR-RFLP markers confirmed the existence of three tRNALeu types of A. pinguis (A–C) within the specimens derived from 21 populations. Sympatric populations of different tRNALeu types were found in lowland and mountain regions. No clear correlation between stand type and the presence of two tRNALeu types (A, B) was observed, as both were growing on soil, humus, and rocks. The tRNALeu type C was found only on humus and its distribution was restricted to low-lying northern populations. The above results indicate that the A. pinguis complex is highly differentiated at the molecular level and may represent three cryptic species. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 155, 273–282.

Marchantia polymorpha L.: A Bioaccumulator

Mussoorie in the western Himalayas of India, a popular tourist destination, was selected for air pollution monitoring. The study was carried out applying thalloid liverwort species Marchantia polymorpha L. as a tool. Moss bags containing M. polymorpha was transplanted at residential, highly and less polluted areas to obtain comprehensive and comparative data. Lead content, along with some essential micronutrients viz. zinc, manganese, and copper, as well as some physiological parameters total chlorophyll, sugar, protein, catalase and peroxidase activity were analyzed. The highest accumulation of lead (Pb) in M. polymorpha plants was highest in summer season , i.e., 2276 μg/g dry weight. The correlation of metals and physiological parameters has been made to get clear view of the effects of lead on physiology and essential micronutrients.

Bryophyte phylogeny: Advancing the molecular and morphological frontiers

Abstract Revolutionary new concepts of bryophyte relationships have emerged from molecular phylogenetic analyses conducted since the onset of the 21st century. For example, sequence data contradict the historical notion that isophylly in leafy liverworts is plesiomorphic and that simple thalloid liverworts are monophyletic. Also contrary to traditional views are the concepts that Leiosporoceros is genetically distinct from other hornworts and that Oedipodium is sister to the peristomate mosses. Substantial increases in ultrastructural and anatomical data likewise have provided new insights on interrelationships. Because of this recent deluge in evolutionary studies on bryophytes, it is an opportune time to co-examine contemporary morphological knowledge and novel molecular hypotheses. An understanding of bryophyte evolution and biology is essential to identify structural innovations that accompanied early land colonization and to illuminate the evolution of more complicated body plans in tracheophytes. In...

NEW HIGHER TAXA OF COMPLEX THALLOID LIVERWORTS (MARCHANTIOPHYTA – MARCHANTIOPSIDA)

Recent studies on molecular phylogeny of complex thalloid liverworts (Marchantiopsida) have revealed the need to recognize four new higher taxa: Family Neohodgsoniaceae, Order Neohodgsoniales, Order Lunulariales and Family Dumortieraceae. These are formally described along with notes on their differences from other complex thalloid liverworts.

Isolation and Structures of New Cyclomyltaylane and ent-Chamigrane-Type Sesquiterpenoids from the Liverwort Reboulia hemishaerica and Their Biotransformation by the Fungus Aspergillus niger

Reboulia hemisphaerica, the thalloid liverwort, contained four new cyclomyltaylane- and two new ent-beta-chamigrane-type sesquiterpenoids of which the absolute stereostructures were established by a combination of two-dimensional NMR spectroscopy, X-ray crystallographic analysis, and the modified Mosher's method. Cyclomyltaylan-5alpha-ol and ent-beta-chamigren-1alpha-ol were biotransformed by the fungus Aspergillus niger to afford new oxygenated matabolites. Their structures were also elucidated in the same manner as described above.

Evolutionary trends in the simple thalloid liverworts (Marchantiophyta, Jungermanniopsida subclass Metzgeriidae)

AbstractThe phylogenetic history of and evolutionary trends within the simple thalloid liverworts (Jungermanniopsida, subclass Metzgeriidae) are reconstructed in a combined analysis of molecular and morphological data. The molecular dataset comprises loci from all three genomes, including trnL-F, rps4, rbcL, atpβ and psbA from the chloroplast, SSU rRNA and LSU rRNA from the nucleus, and nad5 from the mitochondrion, and 65 characters are scored in the morphological dataset. An initial analysis of a molecular dataset that included 16 outgroup and 50 ingroup taxa resolved a Haplomitrium/Treubiaceae clade as the earliest diverging lineage of the ingroup. Subsequent analyses of ingroup only datasets, rooted on this clade, resolve Metzgeriidae as paraphyletic, with Blasiaceae sister to Marchantiopsida in all analyses. A combined analysis of morphological and molecular datasets resolves basically the same clades as analyses of the molecular dataset alone, except for the resolution of a weak sister group relationship between Metzgeriineae and the leafy liverworts. Reconstructions of morphological character evolution on the combined analysis topology confirm that there is substantial homoplasy in the morphology dataset, even in characters that have been traditionally considered diagnostic of hierarchial relationships, such as apical cell geometry, calyptral type and capsule wall thickness. Ancestral state reconstructions contradict many prevailing hypotheses of character evolution in hepatics, including the model of the ancestral liverwort prototype as an erect, radially symmetric plant. Instead, a more likely model is a prostrate, bilaterally symmetric plant with the diagnostic features of a simple thalloid liverwort.

3- O-Methylrhamnose in lower land plant primary cell walls

Acid hydrolysis of cell wall-rich material derived from the young photosynthetic tissues of lower land plants and charophytes yielded an unusual sugar. This sugar was identified as 3- O-methylrhamnose (trivial name acofriose) by its 1H and 13C NMR spectra. In addition to the usual major monosaccharides (glucose, galactose, mannose, arabinose, xylose, rhamnose, glucuronic acid and galacturonic acid) acofriose was released from cell walls of three charophytic algae ( Chara coralina, Coleochaete scutata and Klebsormidium flaccidium), a hornwort ( Anthoceros caucasicus), leafy and thalloid liverworts, mosses and homosporous lycopodiophytes ( Lycopodium pinifolium, Huperzia selago and Diphasiastrum alpinum). The yield of acofriose approximately equalled that of rhamnose. Acofriose was not detectable in the cell walls of a heterosporous lycopodiophyte, a eusporangiate fern, or any of several leptosporangiate ferns, gymnosperms and angiosperms. Our results show that the primary cell walls of lower land plants and their charophyte ancestors are qualitatively different from those of higher plants: the loss of rhamnose methylation supports the generalisation that major steps in plant evolution have required significant changes in cell wall composition.

α-d-Glucuronosyl-(1→3)-l-galactose, an unusual disaccharide from polysaccharides of the hornwort Anthoceros caucasicus

Acid hydrolysis of cell wall-rich material from thalli of the hornwort Anthoceros caucasicus yielded substantial amounts of an unusual disaccharide (1). Hydrolysis of 1 yielded only GlcA, Gal and unhydrolysed 1. Compound 1 was identified as α-d-GlcpA-(1→3)-l-Gal by 1H and 13C NMR spectroscopic analysis and by the susceptibility of its monosaccharide units to phosphorylation by enantiomer-specific kinases. Compound 1 was not detected in acid hydrolysates of other land plants including mosses, leafy and thalloid liverworts, lycopodiophytes and euphyllophytes; it was also absent from charophytes. The Anthoceros polysaccharide that yields 1 was partially extractable in cold aqueous buffer (pH 4.7) and Na2CO3, but not in EDTA or NaOH, suggesting that it was not a typical pectin or hemicellulose. The yield of 1 from various polysaccharide fractions correlated with the yields of Xyl, suggesting a previously unreported polymer containing d-GlcA, l-Gal and Xyl. The existence of a unique polysaccharide in an evolutionarily isolated plant (Anthoceros) supports the view that major steps in plant phylogeny were accompanied by significant changes in cell wall composition.

Subterranean gametophytic axes in the primitive liverwort Haplomitrium harbour a unique type of endophytic association with aseptate fungi.

• Haplomitrium, a primitive liverwort taxon with only remote affinities to other liverwort groups, develops root-like subterranean axes harbouring fungal endophytes. Here we report on the fungal association in H.gibbsiae and H.ovalifolium, using light and electron microscopy. • The epidermal cells of subterranean axes secrete abundant mucilage that harbours aseptate fungal hyphae. The fungus penetrates the epidermal cells and forms intracellular arbuscules invested by the host cytoplasm. Infection is restricted to epidermal cells in H.gibbsiae, whereas in H.ovalifolium the fungus also infects the cortical cells immediately adjacent, where it forms prominent swellings ('lumps'). In H.gibbsiae similar fungal swellings are formed in the epidermal cells along with arbuscules. In both species the lumps undergo cytoplasmic degeneration and collapse, showing a shorter lifespan than the arbuscules. • The fungal infection in Haplomitrium presents affinities with symbiotic associations with glomeromycotean fungi in higher plants (arbuscular mycorrhizas) and thalloid liverworts. However, the pattern of fungal morphogenesis in Haplomitrium has no precedent in bryophytes nor in higher plants. • Considering the Glomeromycota as the most ancient lineage of mycorrhizal fungi, and Haplomitrium as basal in land plant phylogenies, the association described here may be the most primitive land plant-fungal symbiosis documented to date.

Contributions toward a Monograph of Petalophyllum (Marchantiophyta)

The simple thalloid liverwort genus Petalophyllum J. G. C. Lehmann is removed from the Fossombroniaceae and sequestered in the new family Petalophyllaceae along with Sewardiella S. R. Kashyap, a monotypic genus endemic to the In- dian subcontinent. Unlike the Fossombroniaceae, the thallus in the Petalophyllaceae is never dis- sected, the archegonia are clustered rather than scattered, a pseudoperianth is formed rather than a caulocalyx, and the capsule wall is 3-4-layered with outer wall thickenings, which are lacking in the Fossombroniaceae. The North American rep- resentative of Petalophyllum previously considered conspecific with the European taxon P. ralfsii (W. M. Wilson) J. G. C. Lehmann is here described as a distinct species, P. americanum. This is based upon clear differences of the thallus, pseudoper- ianth, and the elater spirals. Furthermore, the ap- plication of the name P. australis Colenso to New Zealand plants is shown to be incorrect; those plants previously referred there represent a new species, P. hodgsonii. This species resembles P. ralfsii, but differs from it in the broad, strongly flat- tened thallus midrib and structure of the female inflorescence.

High rates of extracellular superoxide production in bryophytes and lichens, and an oxidative burst in response to rehydration following desiccation

Summary The mechanism of extracellular superoxide radical (O2·−) formation and the role of the oxidative burst in response to desiccation stress is reported here in bryophytes and lichens from habitats of contrasting water availability. Rates of extracellular production of O2·− radicals were measured, before and after desiccation stress, by the oxidation of epinephrine to adrenochrome, determined spectrophotometrically. Several desiccation‐sensitive lichens and bryophytes that grow in very wet microhabitats produced O2·− extracellularly at high rates, even when they were not stressed. In addition, some species showed a powerful burst of O2·− production during rehydration following desiccation. Production of high levels of O2·− and the existence of an inducible oxidative burst was best developed in cyanobacterial lichens, a hornwort and the two thalloid liverworts tested. Extracellular production of O2·− was almost absent from all mosses tested, a leafy liverwort, a filmy fern and from desiccation‐tolerant lichens. Patterns of O2·− production are discussed in terms of their possible role as a defence against pathogenic fungi and bacteria.

Symbiotic fungal associations in ‘lower’ land plants

An analysis of the current state of knowledge of symbiotic fungal associations in 'lower' plants is provided. Three fungal phyla, the Zygomycota, Ascomycota and Basidiomycota, are involved in forming these associations, each producing a distinctive suite of structural features in well-defined groups of 'lower' plants. Among the 'lower' plants only mosses and Equisetum appear to lack one or other of these types of association. The salient features of the symbioses produced by each fungal group are described and the relationships between these associations and those formed by the same or related fungi in 'higher' plants are discussed. Particular consideration is given to the question of the extent to which root fungus associations in 'lower' plants are analogous to 'mycorrhizas' of 'higher' plants and the need for analysis of the functional attributes of these symbioses is stressed. Zygomycetous fungi colonize a wide range of extant lower land plants (hornworts, many hepatics, lycopods, Ophioglossales, Psilotales and Gleicheniaceae), where they often produce structures analogous to those seen in the vesicular-arbuscular (VA) mycorrhizas of higher plants, which are formed by members of the order Glomales. A preponderance of associations of this kind is in accordance with palaeohbotanical and molecular evidence indicating that glomalean fungi produced the archetypal symbioses with the first plants to emerge on to land. It is shown, probably for the first time, that glomalean fungi forming typical VA mycorrhiza with a higher plant (Plantago lanceolata) can colonize a thalloid liverwort (Pellia epiphylla), producing arbuscules and vesicles in the hepatic. The extent to which these associations, which are structurally analogous to mycorrhizas, have similar functions remains to be evaluated. Ascomycetous associations are found in a relatively small number of families of leafy liverworts. The structural features of the fungal colonization of rhizoids and underground axes of these plants are similar to those seen in mycorrhizal associations of ericaceous plants like Vaccinium. Cross inoculation experiments have confirmed that a typical mycorrhizal endophyte of ericaceous plants, Hymenoscyphus ericae, will form associations in liverworts which are structurally identical to those seen in nature. Again, the functional significance of these associations remains to be examined. Some members of the Jungermanniales and Metzgeriales form associations with basidiomycetous fungi. These produce intracellular coils of hyphae, which are similar to the pelotons seen in orchid mycorrhizas, which also involve basidiomycetes. The fungal associates of the autotrophic Aneura and of its heterotrophic relative Cryptothallus mirabilis have been isolated. In the latter case it has been shown that the fungal symbiont is an ectomycorrhizal associate of Betula, suggesting that the apparently obligate nature of the association between the hepatic and Betula in nature is based upon requirement for this particular heterotroph.

Ethnotherapeutics Of Bryophyte Plagiochasma Appendiculatum Among The Gaddi Tribes Of Kangra Valley, Himachal Pradesh, India

The use of thalloid liverwort Plagiochasma appendiculatum Lehm. et. Lind. by Gaddi tribes of Kangra Valley, Himachal Pradesh in India, for the cure of burns, boils, and blisters of skin is reported for the first time.

Plant mitochondrial RNA editing.

RNA editing affects messenger RNAs and transfer RNAs in plant mitochondria by site-specific exchange of cytidine and uridine bases in both seed and nonseed plants. Distribution of the phenomenon among bryophytes has been unclear since RNA editing has been detected in some but not all liverworts and mosses. A more detailed understanding of RNA editing in plants required extended data sets for taxa and sequences investigated. Toward this aim an internal region of the mitochondrial nad5 gene (1104 nt) was analyzed in a large collection of bryophytes and green algae (Charles). The genomic nad5 sequences predict editing in 30 mosses, 2 hornworts, and 7 simple thalloid and leafy liverworts (Jungermanniidae). No editing is, however, required in seven species of the complex thalloid liverworts (Marchantiidae) and the algae. RNA editing among the Jungermanniidae, on the other hand, reaches frequencies of up to 6% of codons being modified. Predictability of RNA editing from the genomic sequences was confirmed by cDNA analysis in the mosses Schistostega pennata and Rhodobryum roseum, the hornworts Anthoceros husnotii and A. punctatus, and the liverworts Metzgeria conjugata and Moerckia flotoviana. All C-to-U nucleotide exchanges predicted to reestablish conserved codons were confirmed. Editing in the hornworts includes the removal of genomic stop codons by frequent reverse U-to-C edits. Expectedly, no RNA editing events were identified by cDNA analysis in the marchantiid liverworts Ricciocarpos natans, Corsinia coriandra, and Lunularia cruciata. The findings are discussed in relation to models on the phylogeny of land plants.

Studies of Specialized Pitted Parenchyma Cells of the Liverwort Conocephalum Hill and Their Phylogenetic Implications

Except for a few members of the Metzgeriidae, occurrences of specialized conducting tissues are undocumented in liverworts. There have been reports, however, that some liverworts, including the complex thalloid liverwort Conocephalum Hill, possess strands of elongate cells with variously thickened and/or pitted walls. In Conocephalum these specialized cells are ornamented with unpigmented anastomosing bands and have many circular, pit‐like structures in their walls. SEM studies show that the anastomosing striae are visible only on inner wall surfaces. In Conocephalum japonicum (Thunb.) Grolle, many circular, thin‐walled pits are scattered on the lateral walls. Conocephalum conicum (L.) Dumort. may occasionally perforate at the pits to form open pores between cells. TEM micrographs verify that the reticulations of Conocephalum are deposited as primary wall thickenings to the inside of the middle lamella. Primary pit fields are formed on both lateral walls and end walls in C. conicum but are found on lateral walls only in C. japonicum. Many plasmodesmata and desmotubules are observed in the primary pit fields. Histochemical studies demonstrate that the wall thickenings are nonlignified cellulose deposits and that callose is absent from the primary pit fields. The nucleus remains in some of the specialized pitted cells but is absent in others. Positive acid phosphatase activity, which indicates the occurrence of some protoplasmic hydrolysis, is found in some of the specialized cells, which are scattered through both younger and older thallus tissues. Studies of water‐conducting potential demonstrate that, while the specialized pitted cells in the vegetative thalli and archegoniophores of Conocephalum do not form a continuous water‐conducting strand, they do facilitate absorption of water from the rhizoids into the thallus and archegoniophore, respectively. These specialized pitted cells of Conocephalum are not directly homologous to metzgerialean water‐conducting cells, moss hydroids and leptoids, or G‐type and S‐type water‐conducting cells of early fossil land plants, although there are some shared characters with each of these cell types.

Water-relations parameters of some bryophytes evaluated by thermocouple psychrometry

Water-relations parameters are presented for four mosses, and for four leafy and four thalloid liverworts. Osmotic potentials of mosses and leafy liverworts at full turgor mostly lie in the range −1.0 to −1.5 MPa; multistratose thalloid liverworts generally give values in the range −0.5 to −1.0 MPa. These figures are less negative than older measurements based on plasmolysis, which more nearly reflect osmotic potential at turgor loss. Full-turgor water content can generally be estimated with fair accuracy from the graph of water content against water potential; careful blotting of saturated material may give acceptable approximate values for many purposes. Mosses and leafy liverworts of well-drained habitats generally have full-turgor water contents in the range 100-300% dry weight; values for thalloid liverworts may be much higher. Full-turgor water content (as % d.w.) varies seasonally, being high in new growth, and falling progressively through the growing season. The bulk modulus of elasticity (εB) is low (implying highly extensible cell walls) in most thalloid liverworts, and in such desiccation-tolerant mosses as Syntrichia ruraliformis and Racomitrium lanuginosum, but reaches values of 12-20 or more in some leafy liverworts with more rigid cells. Variation in water-relations parameters shows less relation to habitat than might be expected, probably because even in dry habitats bryophytes are fully hydrated for most of the time they are metabolically active, and only suffer water stress transiently as they dry out.