Phylloclade development in the Asparagaceae: an example of homoeosis (original) (raw)
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2016
Abstract: Confocal laser scanning microscopy was utilized to compare the chloroplast morphology and ontogeny among five strains of the green alga Asterochloris. Parsimony analysis inferred from the rDNA ITS sequences confirmed their placement in three distinct lineages: Asterochloris phycobiontica, Trebouxia pyriformis and Asterochloris sp. Examination by confocal microscopy revealed the existence of interspecific differences in the chloroplast ontogeny of Asterochloris; this was based upon either specific chloroplast structures observed in a single species, or on the differential timing of particular ontogenetic sequences. The occurrence of flat parietal chloroplasts prior to cell division, considered as a basic morphological discriminative character of Asterochloris, was clearly associated with the process of aplanosporogenesis. By contrast, chloroplast transformation prior to the formation of autospores proceeded simply by the multiple fission of the chloroplast matrix in the cel...
Phylogeny of the Asparagales based on three plastid and two mitochondrial genes
American Journal of Botany, 2012
Premise of the study: The Asparagales, with ca. 40% of all monocotyledons, include a host of commercially important ornamentals in families such as Orchidaceae, Alliaceae, and Iridaceae, and several important crop species in genera such as Allium , Aloe , Asparagus , Crocus , and Vanilla. Though the order is well defi ned, the number of recognized families, their circumscription, and relationships are somewhat controversial.
Systematic root anatomy of Asparagales and other monocotyledons
Plant Systematics and Evolution, 2000
Root anatomy of several taxa of Asparagales and some taxa formerly included in Asparagales is described in a systematic context together with a literature review. The presence of a dimorphic outer layer with long and short cells is widespread in monocotyledons, indicating that it originated early in the monocot lineage, but whereas this layer is rhizodermal in most monocotyledons, in Asparagales and Araceae it is usually hypodermal. There may be a correlation between the presence of a velamen or a persistent rhizodermis in many Asparagates and Araceae and the presence of a dimorphic hypodermal layer. Many other root anatomical characters, such as the presence of vascular bundles in the central pith and a multi-layered sclerenchymatous cylinder, are probably xeromorphic and developed convergently.
Pappus and cypsela ontogeny in Asteraceae: structural considerations of the tribal category
Revista Mexicana de Biodiversidad, 2014
Crepis japonica (L.) Benth., Porophyllum ruderale (Jacq.) Cass. and Tridax procumbens L. are weedy species that grow in cultivated fields, roadsides, abandoned fields and open, disturbed spaces in Maringa, Parana state, Brazil. The ontogeny of the fruits and seeds of the 3 Asteraceae species was carried out. The flowers and developing fruits were prepared according to resin inclusion techniques for histochemical tests and scanning electron microscopy. During maturation of the pericarp, processes such as trichome differentiation, tissue sclerification, phytomelanin deposition and breakdown of tissues can be observed. The fruit of C. japonica is entirely lacking in phytomelanin. The seed is only exotestal in C. japonica. Comparative analysis of the pappus and cypsela characters demonstrated that they are efficient in separating species and tribes. The seed coat and embryo may also be useful in the characterization of tribes.
DIVERSITY OF CYPSELAR FEATURES IN SIX SPECIES OF THE TRIBE LACTUCEAE (ASTERACEAE)
Abstract Mature cypselas of 6 species belonging to 6 genera {Picris L. SonchusL. Tragopogon L., Chondrilla L., Chichorium L., Hieracium W. & K. ex.Willd.) of the tribe Lactuceae (Asteraceae) have been studied morphologically and anatomically with the help of light microscope. Special emphasis has been given on the size, shape, surface ornamentation of cypsela, nature of ridge and furrow, structure of carpopodium, structure and distribution of pappus, epidermal cell pattern, presence or absence of stylopodium.Carpopodium exist in 3 species but absent in other 3 species (Sonchus oleraceus, Tragopogon orientalis, Chondrilla juncea). It is usually ring like, symmetric but it has one marked interruption in Haeracium racemosum. Cells are generally thick-walled, 3-6 seriate; seldom cells are perforated as in Haeracium racemosum and Picris hieracioides.Pappus is generally present, scabrous to plumose type, but minute obtuse scale like in Chichoriumintybus and apical barbs of pappus is curved in Sonchus oleraceous; persistent or deciduous, homomorphic or heteromorphic, 0.5 - 20 mm. long. All species have pericarpic zone, which in clearly differentiated into epicarpic zone and mesocarpic zone. Epicarpic zone is generally uniseriate, but 2-3 seriate at the ridges in Picris hieracioides, parenchymatous, thickly cuticularised. Mesocarpic zone is represented by a cylindrical tissue either formed by one or two types of cells (thick-walled parenchymatous and sclerenchymatous cells). Some thick-walled parenchyma cells in the epicarpic zone and mesocarpic zone contain brown substances in some of the studied genera. Vascular traces present within the mesocarpic zone and usually exist within the sclerenchyma tissue, but vascular trace is clearly visible within the testa in Tragopogon orientalis. Pitted parenchyma cells are present in some members as Sonchus oleraceous and Chondrilla juncea. Testa is secondarily separated from the pericarp in some genera but generally adpressed with the pericarp. Outer zone of testa is made up of single layered parenchyma cells i.e. testal epidermis and inner zone of testa is represented by a narrow layer of collapsed cells in most of the studied genera, but in Tragopogon orientalis has distinct testal epidermis and testal inner zone (5-6 cells thick). Outer layer of the cotyledon is tangentially elongated, while inner cells are irregularly oriented and all are with dense cytoplasm and granular substances. Some genera have secondary ducts in the cotyledons. Key words : Diversity, Cypselas, Six species, Lactuceae, Asteraceae.
Organisms Diversity & Evolution, 2002
Phylogenetic studies using DNA sequences of two chloroplast regions, rbcL and trnL-F, demonstrate that the proposed genus Ceterach is a small clade within the large genus Asplenium, and sister to the Phyllitis clade. The Ceterach clade is characterised by irregular anastomosing veins and often densely scaled leaf blades. Its taxonomic status as a group nested within Asplenium is confirmed, and it is accepted here as a subgenus with seven species. The Ceterach clade comprises four lineages that correspond to disjunct polyploid complexes: the A. aureum clade forming a polyploid complex (4×, 6×, 8×) in Macaronesia, the A. ceterach clade forming a polyploid complex (2×, 4×, 6×) in the Mediterranean Basin, the A. paucivenosum clade (4×, 6×) in central Asia, and the A. dalhousiae clade (2×) with a disjunct distribution in the Himalaya, Yemen and Eritrea, and southwestern North America. Asplenium paucivenosum is sister to all other members of the Ceterach clade, whereas A. dalhousiae is sister to the A. aureum clade that includes tetraploid A. aureum, hexaploid A. lolegnamense, and octoploid A. parvifolium. Asplenium ceterach and its variations -including the hexaploid A. ceterach subsp. mediterraneum subsp. nov. first described below -form a monophyletic unit, sister to a clade consisting of A. aureum and A. dalhousiae. Asplenium cordatum from Africa and A. haugthonii from the isolated atlantic island of St. Helena are not members of the Ceterach clade, which suggests that leaf blades with dense indumenta have evolved at least twice within asplenioid ferns. The allotetraploid species A. hybridum has the chloroplast DNA from A. ceterach, and therefore the latter species is the maternal ancestor of the former. The other parent of this hybrid species is A. sagittatum that is nested within the sister clade of Ceterach, the Phyllitis clade comprising A. sagittatum and A. scolopendrium.The findings suggest that the current distribution of Ceterach is either the result of long-distance dispersal or represents fragmented relicts of a previously more widely distributed species.
Evolutionary origin of the Asteraceae capitulum: Insights from Calyceraceae
American Journal of Botany, 2012
The interpretation of complex plant structures has been historically based on generalizations of comparative morphology, anatomy, and development. But the relatively recent development of phylogenies based on molecular data are revealing that such morphological generalizations often obscure variation and developmental patterns important for understanding the evolution of diversity of forms, key innovations, and evolutionary constraints or potential. Among angiosperms, the infl orescences of Asteraceae and its near relatives well illustrate the problem that generalizations pose to understanding the evolution of complex structures. Within the fl owering plant order Asterales, the Menyanthaceae, Goodeniaceae, Calyceraceae, and Asteraceae form a clade (the MGCA clade) that is well supported by both molecular and morphological data (Lundberg and Bremer, 2003 ; Lundberg, 2009 ; Tank and Donoghue, 2010). Within this clade, infl orescence morphology is varied and evolutionarily poorly understood.
Morphological characters add support for some members of the basal grade of Asteraceae
Botanical Journal of the Linnean Society, 2013
Recent molecular studies in Asteraceae have divided tribe Mutisieae (sensu Cabrera) into 13 tribes and eight subfamilies. Each of the major clades is well supported but the relationships among them are not always clear. Some of the new taxa are easily characterized by morphological data but others are not, chief among the latter being three subfamilies (Stifftioideae, Wunderlichioideae and Gochnatioideae) and the tribe Hyalideae. To understand evolution in the family it is critical to investigate potential morphological characters that can help to evaluate the basal lineages of the Asteraceae. The data for this study were taken from 52 species in 24 genera representing the basal groups in the family. Many characters were examined but most of the useful ones were from reproductive structures. Several apomorphies supported a few of the clades. For instance, members of subfamily Wunderlichioideae (Hyalideae and Wunderlichieae) share predominantly ten-ribbed achenes and members of Wunderlichioideae + Stifftioideae share two synapomorphies: 100-150 (200) pappus elements, arranged in (three) four or five series. These apomorphies can be viewed as an indication of a sister-group relationship between the two subfamilies as the placement of Stifftieae was not well resolved by the molecular data. Members of Wunderlichieae are characterized by having a paleaceous receptacle, style branches that are strongly papillose above and below the bifurcation, and a pappus of scales. Hyalis and Ianthopappus (Hyalideae) share venation type and an apiculate anther appendage but these are also found in Gochnatieae. Other clades have fewer supporting characters. These characters are just a beginning. Cladograms with morphology characters plotted, illustrations and a key to the basal grade of Asteraceae are provided.