The Brazilian genus Diplusodon is the second largest genus within Lythraceae. Their 85 species oc... more The Brazilian genus Diplusodon is the second largest genus within Lythraceae. Their 85 species occupy diverse habitats within the ‘cerrado’ vegetation, and range from shrubs and treelets to dwarf, xylopodium-bearing subshrubs. A comparative-morphological survey of their inflorescence structures using Trollian typology is here presented, as well as some evolutionary considerations drawn from mapping inflorescence characters onto a preliminary phylogeny. The inflorescences of Diplusodon are mostly polytelic, ranging from single racemes to more or less complex double-, triple-, and multiple-racemes. Frondose, compound racemes are plesiomorphic within the genus. Nevertheless, an array of derived features has been found among their species, including production of lateral cymes, proliferation of the main axis, diverse patterns of internode elongation, reduction of subtending leaves to bracts, development of accessory branches, paedomorphic flowering, and, in three species, reversion to monotely.
Chromosome numbers were counted in 126 new accessions of 50 Paspalum species from Brazil, Argenti... more Chromosome numbers were counted in 126 new accessions of 50 Paspalum species from Brazil, Argentina, Paraguay and Bolivia. The chromosome numbers 2n=12, 20, 24, 30, 40, 50, 60, 80 were confirmed. Chromosome numbers for P. arenarium (2n=20), P. barretoi (2n=20), P. aff. ceresia (2n=40), P. corcovadense (2n=20), P. crispulum (2n=20), P. flaccidum (2n=40), P. nummularium (2n=20), P. scalare (2n=20), P. vescum (2n=20) and P. rectum (2n=20) and a diploid cytotype of P. malacophyllum are reported for the first time. The predominance of tetraploid accessions (43.6%) was confirmed, but an unusually high number of diploid species (44%) and accessions (35.7%) was found. These results open new perspectives for breeding programs, phylogenetic studies, and for research on apomixis control, since diploids of Paspalum are typically sexual.
A survey of branching patterns occurring within Digitaria sect. Trichachne is presented. The gene... more A survey of branching patterns occurring within Digitaria sect. Trichachne is presented. The general growth form type can be characterized as ‘lax tuft’. The proximal portion of the tillers is typically plagiotropous and bears short internodia. It is usually thickened and corm-like. Nevertheless, in D. swalleniana and D. catamarcensis the internodia are elongated and form a well-developed rhizome. In all cases this region of the culm bears cataphylls and behaves as an innovation zone. The culms grow upright to form synflorescences composed of a main flowering unit which can be accompanied by proximal enrichment shoots.As usual among grasses, the synflorescences are polytelic, and comprise a distal portion bearing short paraclades composed each of two spikelets, and a proximal portion bearing long paraclades, each reproducing the structure of the distal portion. All axes bear terminal spikelets. The number of long paraclades shows a wide range of variation within the section, ranging from a 1 or 2 paraclades in D. tenuis and D. brownii to about 50 in D. insularis and D. laxa. Second order long paraclades only were observed in D. laxa. The short paraclades occur always in two rows along inflorescence axes, but the arrangement of long paraclades is usually polystichous. Some controversial issues related to branching patterns are discussed on the basis of SEM-observations.
The inflorescences of the genus Nassauvia are analyzed following Troll’s comparative-morphologica... more The inflorescences of the genus Nassauvia are analyzed following Troll’s comparative-morphological approach. Eight types of synflorescences are recognized, each defined by a particular combination of six developmental processes: truncation, proliferation, shortening of internodes, homogenization of paraclades, suppression of paraclades and shortening of peduncles. Decomposing each inflorescence type into six characters, each referring to a hypothesized developmental process, makes the data suitable for cladistic analysis. The synflorescence patterns described in the present analysis mostly correlate with currently accepted infrageneric classifications; discrepancies are discussed. Inflorescences currently described as „pseudocephalia” are shown to be strongly condensed panicles or stachyoids of heads. Sister group inspection suggests the condensed panicle of heads to be the basal inflorescence condition within the genus Nassauvia.
Paspalum modestum and P. wrightii are perennial grasses growing in permanent and seasonally flood... more Paspalum modestum and P. wrightii are perennial grasses growing in permanent and seasonally flooded areas, respectively. The former produces short rhizomes and floating culms, the latter forms long rhizomes and erect culms. Variations in percentage aerenchymatous space (PAS) in different organs as a response to flooding was analysed using a clone of each species. Eighteen plantlets of each clone were cultivated during 7 months under flooded vs. unflooded conditions. After this period, roots, rhizomes, culms, and leaf sheaths were collected and prepared. PAS was measured using an image analysis device, and data were analysed using ANOVA.Production of aerenchyma took place in both species within the cortical parenchyma of roots, rhizomes and culms, and the mesophyll of leaf sheaths, both in flooded and unflooded plants. Under flooding conditions PAS increased in both species, although the individual response of organs differed: whereas in P. modestum PAS increased primarily in substratum-fixed roots, in P. wrightii all organs produced additional aerenchyma uniformly. Contrasting responses are understood as adaptations to permanent and seasonal flooding, respectively.
The present work intends to clarify the phylogenetic relationships among the species of Paspalum ... more The present work intends to clarify the phylogenetic relationships among the species of Paspalum L. belonging to the informal groups Notata/Linearia and Dilatata, and to raise some preliminary hypotheses on the phylogeny of the genus as a whole. A combined dataset including morphological and molecular characters was used to analyze 28 species of Paspalum plus some representatives of related genera of the tribe Paniceae. Analyses were performed using both parsimony and maximum likelihood. The monophyly of Paspalum is not supported nor contradicted. The circumscription of informal groups of Paspalum is discussed, as well as the cladistic treatment of allopolyploid taxa, especially those comprising the Dilatata group. The relationships of members of the Dilatata with their putative progenitors is confirmed, but the monophyly of the group as a whole is not. A close relationship between P. dilatatum Poir. and P. lividum Trin. ex Schltdl. is shown. Our analysis is consistent with the monophyly of a group comprising Notata+Linearia, with a monophyletic Notata group nested within it. The delimitation of the core Notata is proposed by including P. conduplicatum Canto-Dorow, Valls and Longhi-Wagner, P. notatum Flüggé, P. minus E. Fourn., P. pumilum Nees and P. subciliatum Chase.
The inflorescences ofPaspalum are composed of a main axis and 1 to more than 100 raceme-like late... more The inflorescences ofPaspalum are composed of a main axis and 1 to more than 100 raceme-like lateral branches arranged along it. Each branch bears two rows of homogeneous subunits composed either of one or two consecutive-ordered axes, each one ending with a spikelet. In terms ofTroll's descriptive and typological system, such lateral branches were regarded as long paracladia which bear homogeneous bi-axial short paracladia. The structural pattern of these long paracladia is considered to be a recapitulation of the distal main-axis structure which was lost by evolutionary truncation. — The occurrence of a main florescence (= terminal spikelet) and a short paracladia-bearing zone at the distal portion of the main axis in several species of the genusPaspalum, as it is exemplified by species belonging to the so-called ‘Quadrifaria group’, seems to support the hypothesis that the usual inflorescence ofPaspalum actually derived from a paniculate structure by evolutionary homogenization and truncation processes. This ‘Quadrifaria-type inflorescences’ would be regarded as an intermediate step in the evolutionary pathway. Nevertheless, the phylogenetic implications of this interpretation remains obscure because at the present time there is not any hypothesis about the phylogeny of the genus available.
The Brazilian genus Diplusodon is the second largest genus within Lythraceae. Their 85 species oc... more The Brazilian genus Diplusodon is the second largest genus within Lythraceae. Their 85 species occupy diverse habitats within the ‘cerrado’ vegetation, and range from shrubs and treelets to dwarf, xylopodium-bearing subshrubs. A comparative-morphological survey of their inflorescence structures using Trollian typology is here presented, as well as some evolutionary considerations drawn from mapping inflorescence characters onto a preliminary phylogeny. The inflorescences of Diplusodon are mostly polytelic, ranging from single racemes to more or less complex double-, triple-, and multiple-racemes. Frondose, compound racemes are plesiomorphic within the genus. Nevertheless, an array of derived features has been found among their species, including production of lateral cymes, proliferation of the main axis, diverse patterns of internode elongation, reduction of subtending leaves to bracts, development of accessory branches, paedomorphic flowering, and, in three species, reversion to monotely.
Chromosome numbers were counted in 126 new accessions of 50 Paspalum species from Brazil, Argenti... more Chromosome numbers were counted in 126 new accessions of 50 Paspalum species from Brazil, Argentina, Paraguay and Bolivia. The chromosome numbers 2n=12, 20, 24, 30, 40, 50, 60, 80 were confirmed. Chromosome numbers for P. arenarium (2n=20), P. barretoi (2n=20), P. aff. ceresia (2n=40), P. corcovadense (2n=20), P. crispulum (2n=20), P. flaccidum (2n=40), P. nummularium (2n=20), P. scalare (2n=20), P. vescum (2n=20) and P. rectum (2n=20) and a diploid cytotype of P. malacophyllum are reported for the first time. The predominance of tetraploid accessions (43.6%) was confirmed, but an unusually high number of diploid species (44%) and accessions (35.7%) was found. These results open new perspectives for breeding programs, phylogenetic studies, and for research on apomixis control, since diploids of Paspalum are typically sexual.
A survey of branching patterns occurring within Digitaria sect. Trichachne is presented. The gene... more A survey of branching patterns occurring within Digitaria sect. Trichachne is presented. The general growth form type can be characterized as ‘lax tuft’. The proximal portion of the tillers is typically plagiotropous and bears short internodia. It is usually thickened and corm-like. Nevertheless, in D. swalleniana and D. catamarcensis the internodia are elongated and form a well-developed rhizome. In all cases this region of the culm bears cataphylls and behaves as an innovation zone. The culms grow upright to form synflorescences composed of a main flowering unit which can be accompanied by proximal enrichment shoots.As usual among grasses, the synflorescences are polytelic, and comprise a distal portion bearing short paraclades composed each of two spikelets, and a proximal portion bearing long paraclades, each reproducing the structure of the distal portion. All axes bear terminal spikelets. The number of long paraclades shows a wide range of variation within the section, ranging from a 1 or 2 paraclades in D. tenuis and D. brownii to about 50 in D. insularis and D. laxa. Second order long paraclades only were observed in D. laxa. The short paraclades occur always in two rows along inflorescence axes, but the arrangement of long paraclades is usually polystichous. Some controversial issues related to branching patterns are discussed on the basis of SEM-observations.
The inflorescences of the genus Nassauvia are analyzed following Troll’s comparative-morphologica... more The inflorescences of the genus Nassauvia are analyzed following Troll’s comparative-morphological approach. Eight types of synflorescences are recognized, each defined by a particular combination of six developmental processes: truncation, proliferation, shortening of internodes, homogenization of paraclades, suppression of paraclades and shortening of peduncles. Decomposing each inflorescence type into six characters, each referring to a hypothesized developmental process, makes the data suitable for cladistic analysis. The synflorescence patterns described in the present analysis mostly correlate with currently accepted infrageneric classifications; discrepancies are discussed. Inflorescences currently described as „pseudocephalia” are shown to be strongly condensed panicles or stachyoids of heads. Sister group inspection suggests the condensed panicle of heads to be the basal inflorescence condition within the genus Nassauvia.
Paspalum modestum and P. wrightii are perennial grasses growing in permanent and seasonally flood... more Paspalum modestum and P. wrightii are perennial grasses growing in permanent and seasonally flooded areas, respectively. The former produces short rhizomes and floating culms, the latter forms long rhizomes and erect culms. Variations in percentage aerenchymatous space (PAS) in different organs as a response to flooding was analysed using a clone of each species. Eighteen plantlets of each clone were cultivated during 7 months under flooded vs. unflooded conditions. After this period, roots, rhizomes, culms, and leaf sheaths were collected and prepared. PAS was measured using an image analysis device, and data were analysed using ANOVA.Production of aerenchyma took place in both species within the cortical parenchyma of roots, rhizomes and culms, and the mesophyll of leaf sheaths, both in flooded and unflooded plants. Under flooding conditions PAS increased in both species, although the individual response of organs differed: whereas in P. modestum PAS increased primarily in substratum-fixed roots, in P. wrightii all organs produced additional aerenchyma uniformly. Contrasting responses are understood as adaptations to permanent and seasonal flooding, respectively.
The present work intends to clarify the phylogenetic relationships among the species of Paspalum ... more The present work intends to clarify the phylogenetic relationships among the species of Paspalum L. belonging to the informal groups Notata/Linearia and Dilatata, and to raise some preliminary hypotheses on the phylogeny of the genus as a whole. A combined dataset including morphological and molecular characters was used to analyze 28 species of Paspalum plus some representatives of related genera of the tribe Paniceae. Analyses were performed using both parsimony and maximum likelihood. The monophyly of Paspalum is not supported nor contradicted. The circumscription of informal groups of Paspalum is discussed, as well as the cladistic treatment of allopolyploid taxa, especially those comprising the Dilatata group. The relationships of members of the Dilatata with their putative progenitors is confirmed, but the monophyly of the group as a whole is not. A close relationship between P. dilatatum Poir. and P. lividum Trin. ex Schltdl. is shown. Our analysis is consistent with the monophyly of a group comprising Notata+Linearia, with a monophyletic Notata group nested within it. The delimitation of the core Notata is proposed by including P. conduplicatum Canto-Dorow, Valls and Longhi-Wagner, P. notatum Flüggé, P. minus E. Fourn., P. pumilum Nees and P. subciliatum Chase.
The inflorescences ofPaspalum are composed of a main axis and 1 to more than 100 raceme-like late... more The inflorescences ofPaspalum are composed of a main axis and 1 to more than 100 raceme-like lateral branches arranged along it. Each branch bears two rows of homogeneous subunits composed either of one or two consecutive-ordered axes, each one ending with a spikelet. In terms ofTroll's descriptive and typological system, such lateral branches were regarded as long paracladia which bear homogeneous bi-axial short paracladia. The structural pattern of these long paracladia is considered to be a recapitulation of the distal main-axis structure which was lost by evolutionary truncation. — The occurrence of a main florescence (= terminal spikelet) and a short paracladia-bearing zone at the distal portion of the main axis in several species of the genusPaspalum, as it is exemplified by species belonging to the so-called ‘Quadrifaria group’, seems to support the hypothesis that the usual inflorescence ofPaspalum actually derived from a paniculate structure by evolutionary homogenization and truncation processes. This ‘Quadrifaria-type inflorescences’ would be regarded as an intermediate step in the evolutionary pathway. Nevertheless, the phylogenetic implications of this interpretation remains obscure because at the present time there is not any hypothesis about the phylogeny of the genus available.
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