Apigenin di-C-glycosylflavones of Angiopteris (Marattiales)

A survey of the flavonoids of four species of Angiopteris indicates that di-C-glycosylflavones and flavone-O-glycosides may be characteristic of this distinct group of eusporangiate ferns. Derivatives of flavonols, which are typical of leptosporangiate ferns and Ophioglossum, or biflavones, which are characteristic of the Psilotaceae, were not detected in Angiopteris.     

Morphologic and taxonomic relationships of the Psilotaceae relative to evolutionary lines in early land vascular plants

Examination of the fossil record shows that there is no direct evidence regarding the origins and early evolution of the Psilotaceae. Past comparisons betweenPsilotum orTmesipteris and certain fossil plants are reviewed. The major types of early land vascular plants are surveyed in order to demonstrate their basic characteristics and evolutionary trends and to point out the absence of any direct links with the Psilotaceae. Fossil plants of problematical affinities which appear to be important in the early diversification of ferns or plants closely related to ferns are discussed. The nature of stem-leaf relationships of some primitive, extant filicalean ferns and possibly the Psilotaceae is considered in terms of possible similar occurrences among fossil plants.     

Sporogenesis in Eusporangiate Ferns: I. Monoplastidic Meiosis in Angiopteris (Marattiales)

Angiopteris (Marattiales) undergoes the more primitive form of monoplastidic meiosis, while other ferns have evolved the polyplastidic type typical of seed plants. In monoplastidic cell division, the single plastid divides and serves as site of the microtubule organizing center (MTOC) for spindle formation resulting in coordinated division of plastid, nucleus, and cytoplasm. In plants with polyplastidic cell division, the MTOC is diffuse and generally perinuclear. Monoplastidic cell division is seen as a plesiomorphic feature that was inherited from algal ancestors containing a single plastid and modified through evolution. Monoplastidic meiosis occurs in all groups of bryophytes (although in only a few hepatics), Isoetes, Selaginella, certain generic segregates of Lycopodium, and in members of the Marattiales. It is not known to occur in psilophytes, Equisetum, leptosporangiate ferns, or seed plants. Received 30 January 2001/ Accepted in revised form 24 April 2001     

A PHYTOCHEMICAL APPROACH TO THE GLEICHENIACEAE

The Gleicheniaceae, containing approximately 120 species, is a family of primitive ferns distributed throughout most of the tropics and subtropics. Historically the family was considered to be monogeneric; however, most recent authors using morphological, anatomical and cytological information have subdivided the group into 5 or 6 distinct genera. Some authors have even elevated certain species to family or ordinal levels (e.g., Platyzoma and Stromatopteris). The distribution of flavonol-3-0-glycosides supports the segregation of the Gleicheniaceae, sensu lato, into at least three groupings. Flavonoids similar to those identified within the Psilotaceae (flavones, biflavones, and C-glycosylflavones) were not detected during this study.     

A SURVEY FOR 1,3,6,7-TETRAHYDROXY-C-GLYCOSYLXANTHONES EMPHASIZING THE “PRIMITIVE” LEPTOSPORANGIATE FERNS AND THEIR ALLIES

A survey for 1,3,6,7-tetrahydroxy-C-glycosylxanthones of representative species within the primitive vascular plants, emphasizing the leptosporangiate ferns, has indicated a limited distribution of these compounds within three leptosporangiate families: Hymenophyllaceae, Aspleniaceae and Marsileaceae. In the Hymenophyllaceae the distribution of these compounds appears to be a useful criterion for segregating species of Mecodium from other species of Hymenophyllum (sensu lato) and suggests that the tubulate vs. the valvate indusial condition may not be an ideal character for separating all species of Hymenophyllum (s.l.) from those of Trichomanes (s.l.). These compounds appear useful for delimiting several species of Elaphoglossum section Pachyglossa and support a relationship among the Aspleniaceae, Athyriaceae, and Elaphoglossaceae. Their presence in Marsilea also raises questions as to the origin of this group of plants.     

Chloroplast Genome Evolution in Early Diverged Leptosporangiate Ferns

In this study, the chloroplast (cp) genome sequences from three early diverged leptosporangiate ferns were completed and analyzed in order to understand the evolution of the genome of the fern lineages. The complete cp genome sequence of Osmunda cinnamomea (Osmundales) was 142,812 base pairs (bp). The cp genome structure was similar to that of eusporangiate ferns. The gene/intron losses that frequently occurred in the cp genome of leptosporangiate ferns were not found in the cp genome of O. cinnamomea. In addition, putative RNA editing sites in the cp genome were rare in O. cinnamomea, even though the sites were frequently predicted to be present in leptosporangiate ferns. The complete cp genome sequence of Diplopterygium glaucum (Gleicheniales) was 151,007 bp and has a 9.7 kb inversion between the trnL-CAA and trnV-GCA genes when compared to O. cinnamomea. Several repeated sequences were detected around the inversion break points. The complete cp genome sequence of Lygodium japonicum (Schizaeales) was 157,142 bp and a deletion of the rpoC1 intron was detected. This intron loss was shared by all of the studied species of the genus Lygodium. The GC contents and the effective numbers of co-dons (ENCs) in ferns varied significantly when compared to seed plants. The ENC values of the early diverged leptosporangiate ferns showed intermediate levels between eusporangiate and core leptosporangiate ferns. However, our phylogenetic tree based on all of the cp gene sequences clearly indicated that the cp genome similarity between O. cinnamomea (Osmundales) and eusporangiate ferns are symplesiomorphies, rather than synapomorphies. Therefore, our data is in agreement with the view that Osmundales is a distinct early diverged lineage in the leptosporangiate ferns.     

DIVISION OF THE GENERATIVE CELL AND LATE DEVELOPMENT IN THE MALE GAMETOPHYTE OF GINKGO BILOBA

Division of the generative cell in the male gametophyte of Ginkgo biloba to yield the sterile cell and spermatogenous cell was examined in vivo and in vitro. Evidence is presented in support of a new interpretation of development in which the sterile cell and spermatogenous cell arise from an unusual anticlinal ringlike division of the generative cell. This type of cell division is only known to occur during antheridial development in leptosporangiate ferns and stomatal development among certain ferns in the Schizaeaceae and Polypodiaceae. The strong similarities in development and cell arrangement within the male gametophytes of cycads and Ginkgo suggest that division of the generative cell in cycads may be the same as in Ginkgo. Although the ringlike (conically annular) divisions in the antheridia of leptosporangiate ferns and the male gametophytes of Ginkgo (and probably cycads) are remarkably similar and result in the production of a central spermatogenous cell, it is conjectural as to whether these patterns represent a striking convergence or evolutionary homology.     

COMPARATIVE LEAF STRUCTURE OF SEVERAL SPECIES OF HOMOSPOROUS LEPTOSPORANGIATE FERNS

The structure of the mature leaves of 13 species from 9 families of homosporous leptosporangiate ferns was examined by light and electron microscopy. In 11 species (Adiantum pedatum L., Athyrium angustum Roth., Cyathea dregei Sm., Lygodium palmatum Sw., Mohria caffrorum (L.) Desv., Oleandra distenta Kuntae, Pellaea calomelanos (Sw.) Link, Pityrogramma calomelanos (L.) Link var. austro-americana (Domn.) Farw., Trichomanes melanotrichum Schlechtend., Vittaria guineensis Desv., and Woodwardia orientalis Sw.) the lamina veins are collateral; in two (Phlebodium aureum and Platycerium bifurcatum), bicollateral as well as collateral veins are present. The vascular bundles in the midribs of C. dregei and those in the petioles and midribs of Phlebodium and Platycerium are concentric. All of the vascular bundles in the homosporous leptosporangiate ferns studied are delimited by a tightly arranged cylinder of endodermal cells with Casparian strips. Within the veins without parenchymatic xylem sheaths, some sieve elements commonly abut tracheary elements with hydrolyzed primary walls. The majority of vascular parenchyma cells contact both sieve elements and tracheary elements, although some parenchyma cells are associated with only one type of conducting cell. Transfer cells (parenchyma cells with wall ingrowths) occur in the veins of 6 species examined. Most of the vascular parenchyma cells, however, have no distinctive structural characteristics. The sieve elements of the homosporous leptosporangiate ferns are very similar structurally and each consists of a plasmalemma, a parietal, anastomosing network of smooth endoplasmic reticulum (ER), and variable numbers of refractive spherules, plastids and mitochondria. The sieve elements of L. palmatum also contain plasmalemma tubules. The parenchymatic cells of the leaf (mesophyll, endodermal and vascular parenchyma cells) are united by desmotubule-containing plasmodesmata. The sieve elements are connected to each other by sieve pores and to parenchymatic cells by pore-plasmodesma connections. The sieve-area pores contain variable amounts of membranous material, apparently ER membranes, but do not occlude them. These membranes commonly are found in continuity with the parietal ER of the lumen. Based upon the relative frequencies of cytoplasmic connections between cell types, the photosynthates may move from the mesophyll to the site of phloem loading via somewhat different pathways in different species of homosporous leptosporangiate ferns.     

Reiterative growth in the complex adaptive architecture of the Paleozoic (Pennsylvanian) filicalean fern Kaplanopteris clavata

Reiteration is a widespread component of plant growth whose evolutionary importance in ferns is not recognized widely. We introduce and discuss the growth architecture of Kaplanopteris clavata, a fossil filicalean fern from the Pennsylvanian (ca. 305 million yeas old), focusing on types of reiteration exhibited by this species and on the adaptive and phylogenetic significance of reiteration for ferns in general. Kaplanopteris clavata combines two types of reiterative growth where growth modules are borne on fronds: (1) entire fronds derived from primary pinnae, and (2) epiphyllous plantlets. This combination of reiterative pathways, unique among fossil and living ferns, allowed K. clavata to explore ecospace through an opportunistic combination of scrambling, climbing and epiphytic growth. Kaplanopteris clavata underscores the organographic importance of fronds (as opposed to stems) in the adaptive architecture of ferns, emphasizing functional convergences between the different Baupla̋ne of ferns and angiosperms. This unique combination of reiterative pathways is interpreted as a derived condition illustrating the structural and developmental complexity achieved by some filicaleans during the first major evolutionary radiation of leptosporangiate ferns.     

Morphological functions of gibberellins in leptosporangiate fern gametophytes: insights into the evolution of form and gender expression

In addition to genetic load, the induction of maleness in leptosporangiate gametophytes by the pheromone antheridiogen may facilitate rates of outcrossing similar to those found in angiosperms. The antheridiogens that have been chemically identified are similar to gibberellins and probably evolved from this common plant hormone. The purposes of this study were to determine the functions of endogenous gibberellins in morphological development and gender expression in leptosporangiate fern gametophytes and to elucidate how antheridiogens may have evolved from gibberellin precursors. We grew gametophytes of Osmunda regalis and Athyrium filix‐femina on nutrient agar enriched with APOGEE, which blocks gibberellin synthesis. Osmunda regalis is a member of Osmundaceae, the only family in Osmundales, the sister group of all remaining extant leptosporangiate ferns. This family possesses a male‐first gender in isolation and lacks any known antheridiogen systems. In contrast, A. filix‐femina is a member of a derived family, Woodsiaceae, which possesses antheridiogen systems. Disruption of gibberellin synthesis retarded notch development and expression of both maleness and femaleness (i.e. gender status) in both species. On the basis of these results, we offer a simple model of gametophyte evolution driven by gender‐based fitness gain curves and the influence of exogenous gibberellins. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159 , 599–615.     

中国中生代的马通蕨科植物:化石记录、多样性与时空分布特征*

现生真蕨目马通蕨科(Matoniaceae)植物仅存Matonia和Phanerosorus两属, 集中分布于马来西亚、印度尼西亚等热带地区。马通蕨科植物在中生代时期全球广布, 且主要分布于热带、亚热带地区, 有近9个属, 被作为热带、亚热带气候的标志性植物化石之一。本文梳理总结了中国中生代的马通蕨科化石记录并分析其多样性特征, 共计有2属16种, 包括异脉蕨属(Phlebopteris) 15种和准马通蕨属(Matonidium) 1种。对其化石记录和地质地理分布分析表明, 晚三叠世时期, 异脉蕨属植物广泛分布于热带—亚热带湿热气候区, 包括华南一带的四川、湖北、 云南、西藏、福建等地; 早侏罗世时期, 其分布逐渐向北方扩展, 在南、北方植物区系界线附近均有发现; 中侏罗世局限于湖北、青海等地; 早白垩世时仅在黑龙江和西藏少量发现。准马通蕨属仅在黑龙江地区的早白垩世地层中发现。整体上, 马通蕨科在中国中生代的分布范围变迁与气候带范围变化相吻合。     

Amplification of noncoding chloroplast DNA for phylogenetic studies in lycophytes and monilophytes with a comparative example of relative phylogenetic utility from Ophioglossaceae

Noncoding DNA sequences from numerous regions of the chloroplast genome have provided a significant source of characters for phylogenetic studies in seed plants. In lycophytes and monilophytes (leptosporangiate ferns, eusporangiate ferns, Psilotaceae, and Equisetaceae), on the other hand, relatively few noncoding chloroplast DNA regions have been explored. We screened 30 lycophyte and monilophyte species to determine the potential utility of PCR amplification primers for 18 noncoding chloroplast DNA regions that have previously been used in seed plant studies. Of these primer sets eight appear to be nearly universally capable of amplifying lycophyte and monilophyte DNAs, and an additional six are useful in at least some groups. To further explore the application of noncoding chloroplast DNA, we analyzed the relative phylogenetic utility of five cpDNA regions for resolving relationships in Botrychium s.l. (Ophioglossaceae). Previous studies have evaluated both the gene rbcL and the trnL(UAA)-trnF(GAA) intergenic spacer in this group. To these published data we added sequences of the trnS(GCU)-trnG(UUC) intergenic spacer + the trnG(UUC) intron region, the trnS(GGA)-rpS4 intergenic spacer+rpS4 gene, and the rpL16 intron. Both the trnS(GCU)-trnG(UUC) and rpL16 regions are highly variable in angiosperms and the trnS(GGA)-rpS4 region has been widely used in monilophyte phylogenetic studies. Phylogenetic resolution was equivalent across regions, but the strength of support for the phylogenies varied among regions. Of the five sampled regions the trnS(GCU)-trnG(UUC) spacer+trnG(UUC) intron region provided the strongest support for the inferred phylogeny.     

Cytological features of oogenesis and their evolutionary significance in the fern Osmunda japonica

The development of the egg and canal cells in the fern Osmunda japonica Thunb. was studied during oogenesis by transmission electron microscopy. The mature egg possesses no fertilization pore and no typical egg envelope. In addition, an extra wall formed around the canal cells during oogenesis and apparently blocked protoplasmic connections between the egg and the canal cells. The periodic acid Schiff (PAS) reaction revealed that the extra wall was most likely composed of polysaccharides. Maturation of the egg was accompanied by the formation of a separation cavity above the egg and by some changes in the morphology of the nucleus and cytoplasmic organelles. The chromatin of the nucleus becomes condensed and the upper surface of the nucleus becomes closely associated with the plasmalemma. Amyloplasts in the egg cytoplasm were numerous and conspicuous, with most in close proximity to the nucleus. Finally, the cytoplasm on one side of the egg became vesiculated and the overlying plasmalemma was easily disrupted. These cytological features of the egg and the canal cells during oogenesis in O. japonica are markedly different from those of the leptosporangiate ferns and suggest a significant evolutionary divergence in reproductive cellular features between Osmundaceae and leptosporangiate ferns.     

POLYPHENOLICS OF THE MARSILEACEAE AND THEIR POSSIBLE PHYLOGENETIC UTILITY

Species of the Marsileaceae represent a unique group of pteridophytes of uncertain origin. The polyphenolic profiles of representative species, which include flavonol-3-O-mono- and diglycosides, C-glycosylflavones and C-glycosylxanthones, have chemical features in common with the primitive leptosporangiate ferns, especially the Hymenophyllaceae. Intergeneric relationships in the family based on morphology, cytology, fossil evidence and polyphenolic profiles are discussed.     

Utility of a large, multigene plastid data set in inferring higher-order relationships in ferns and relatives (monilophytes)

? Premise of the Study: The monilophytes (ferns and relatives)-the third largest group of land plants-exhibit a diverse array of vegetative and reproductive morphologies. Investigations into their early ecological and life-history diversification require accurate, well-corroborated phylogenetic estimates. We examined the utility of a large plastid-based data set in inferring backbone relationships for monilophytes. ? Methods: We recovered 17 plastid genes for exemplar taxa using published and new primers. We compared results from maximum-likelihood and parsimony analyses, assessed the effects of removing rapidly evolving characters, and examined the extent to which our data corroborate or contradict the results of other studies, or resolve current ambiguities. ? Key Results: Considering multifamily clades, we found bootstrap support comparable to or better than that in published studies that used fewer genes from fewer or more taxa. We firmly establish filmy ferns (Hymenophyllales) as the sister group of all leptosporangiates except Osmundaceae, resolving the second deepest split in leptosporangiate-fern phylogeny. A clade comprising Ophioglossaceae and Psilotaceae is currently accepted as the sister group of other monilophytes, but we recover Equisetum in this position. We also recover marattioid and leptosporangiate ferns as sister groups. Maximum-likelihood rate-class estimates are somewhat skewed when a long-branch lineage (Selaginella) is included, negatively affecting bootstrap support for early branches. ? Conclusions: Our findings support the utility of this gene set in corroborating relationships found in previous studies, improving support, and resolving uncertainties in monilophyte phylogeny. Despite these advances, our results also underline the need for continued work on resolving the very earliest splits in monilophyte phylogeny.     

The classification of ferns

Intensive morphological studies have been devoted to the more primitive ferns, which represent a small minority of living species, but too little is yet known about the vast majority of other ferns, with the result that recent attempts at a natural classification show considerable differences of treatment.
The problem is complicated by convergent evolution in the characters of almost all parts of a fern plant. Not only similar soral form, but also similar frond form, types of venation, scales, etc. have been developed on different evolutionary lines.
To illustrate the nature of the problem an attempt has been made to state the probable characters of a primitive leptosporangiate fern, and the kinds of ways in which existing ferns have developed from this condition. Evolutionary change in different parts of the plant has proceeded in different ways and to different degrees in the many genera of existing ferns. Primitive characters of one kind or another are shown by a great number of ferns, along with highly advanced characters of other kinds.
Recent schemes of classification are briefly compared, and a summary is given of the author's own scheme, with notes on evolutionary trends in the various groups as he sees them.
Much more information is needed on which to establish a really satisfactory scheme. The present one is put forward in the hope that others will take up the work. With modern facilities for travel, it is to be hoped that more botanists will come to the tropics and see ferns and other too-little-known plants in their native habitats. Morphological study needs to be undertaken with an understanding of the living plant and of its environment.     

Exploring the phylogeny of the marattialean ferns

The eusporangiate marattialean ferns represent an ancient radiation with a rich fossil record but limited modern diversity in the tropics. The long evolutionary history without close extant relatives has confounded studies of the phylogenetic origin, rooting and timing of marattialean ferns. Here we present new complete plastid genomes of six marattialean species and compiled a plastid genome dataset representing all of the currently accepted marattialean genera. We further supplemented this dataset by compiling a large dataset of mitochondrial genes and a phenotypic data matrix covering both extant and extinct representatives of the lineage. Our phylogenomic and total-evidence analyses corroborated the postulated position of marattialean ferns as the sister to leptosporangiate ferns, and the position of Danaea as the sister to the remaining extant marattialean genera. However, our results provide new evidence that Christensenia is sister to Marattia and that M. cicutifolia actually belongs to Eupodium. The apparently highly reduced rate of molecular evolution in marattialean ferns provides a challenge for dating the key phylogenetic events with molecular clock approaches. We instead applied a parsimony-based total-evidence dating approach, which suggested a Triassic age for the extant crown group. The modern distribution can best be explained as mainly resulting from vicariance following the breakup of Pangaea and Gondwana. We resolved the fossil genera Marattiopsis, Danaeopsis and Qasimia as members of the monophyletic family Marattiaceae, and the Carboniferous genera Sydneia and Radstockia as the monophyletic sister of all other marattialean ferns.