Five vicariant genera from Gondwana: the Velloziaceae as shown by molecules and morphology [corrected].

BACKGROUND AND AIMS: The amount of data collected previously for Velloziaceae neither clarified relationships within the family nor helped determine an appropriate classification, which has led to huge discordance among treatment by different authors. To achieve an acceptable phylogenetic result and understand the evolution and roles of characters in supporting groups, a total evidence analysis was developed which included approx. 20 % of the species and all recognized genera and sections of Velloziaceae, plus outgroups representatives of related families within Pandanales. METHODS: Analyses were undertaken with 48 species of Velloziaceae, representing all ten genera, with DNA sequences from the atpB-rbcL spacer, trnL-trnF spacer, trnL intron, trnH-psbA spacer, ITS ribosomal DNA spacers and morphology. KEY RESULTS: Four groups consistently emerge from the analyses. Persistent leaves, two phloem strands, stem cortex divided in three regions and violet tepals support Acanthochlamys as sister to Velloziaceae s.s., which are supported mainly by leaves with marginal bundles, transfusion tracheids and inflorescence without axis. Within Velloziaceae s.s., an African Xerophyta + Talbotia clade is uniquely supported by basal loculicidal capsules; an American clade, Barbacenia s.l. + Barbaceniopsis + Nanuza + Vellozia, is supported by only homoplastic characters. Barbacenia s.l. (= Aylthonia + Barbacenia + Burlemarxia + Pleurostima) is supported by a double sheath in leaf vascular bundles and a corona; Barbaceniopsis + Nanuza + Vellozia is not supported by an unambiguous character, but Barbaceniopsis is supported by five characters, including diclinous flowers, Nanuza + Vellozia is supported mainly by horizontal stigma lobes and stem inner cortex cells with secondary walls, and Vellozia alone is supported mainly by pollen in tetrads. CONCLUSIONS: The results imply recognition of five genera (Acanthochlamys (Xerophyta (Barbacenia (Barbaceniopsis, Vellozia)))), solving the long-standing controversies among recent classifications of the family. They also suggest a Gondwanan origin for Velloziaceae, with a vicariant pattern of distribution.

Primary and secondary thickening in the stem of Cordyline fruticosa (Agavaceae)

The growth in thickness of monocotyledon stems can be either primary, or primary and secondary. Most of the authors consider this thickening as a result of the PTM (Primary Thickening Meristem) and the STM (Secondary Thickening Meristem) activity. There are differences in the interpretation of which meristem would be responsible for primary thickening. In Cordyline fruticosa the procambium forms two types of vascular bundles: collateral leaf traces (with proto and metaxylem and proto and metaphloem), and concentric cauline bundles (with metaxylem and metaphloem). The procambium also forms the pericycle, the outermost layer of the vascular cylinder consisting of smaller and less intensely colored cells that are divided irregularly to form new vascular bundles. The pericycle continues the procambial activity, but only produces concentric cauline bundles. It was possible to conclude that the pericycle is responsible for the primary thickening of this species. Further away from the apex, the pericyclic cells undergo periclinal divisions and produce a meristematic layer: the secondary thickening meristem. The analysis of serial sections shows that the pericycle and STM are continuous in this species, and it is clear that the STM originates in the pericycle.The endodermis is acknowledged only as the innermost layer of the cortex.

O crescimento em espessura do caule de monocotiledônea pode ser primário, ou primário e secundário. A maioria dos autores consideram o espessamento resultante do MEP (Meristema de Espessamento Primário) e do MES (Meristema de Espessamento Secundário). Há divergências de qual seria o meristema responsável pelo espessamento primário. Em Cordyline fruticosa o procâmbio forma feixes vasculares de dois tipos: traços foliares colaterais (com proto e metaxilema e proto e metafloema), e feixes caulinares concêntricos (com metaxilema e metafloema). O procâmbio também forma o periciclo, a camada mais externa do cilindro vascular, constituída por células menores e menos coradas que se dividem irregularmente, formando novos feixes vasculares. O periciclo dá continuidade à atividade procambial, originando somente feixes concêntricos. Concluiu-se ser o periciclo responsável pelo espessamento primário desta espécie. Mais distante do ápice as células pericíclicas passam a sofrer divisões periclinais originando o Meristema de Espessamento Secundário. A análise dos cortes seriados mostra que o periciclo e o MES são contínuos nesta espécie, ficando claro que o periciclo origina oMES. A endoderme é reconhecida, apenas, como a camada mais interna do córtex.

Primary and secondary thickening in the stem of Cordyline fruticosa.

The growth in thickness of monocotyledon stems can be either primary, or primary and secondary. Most of the authors consider this thickening as a result of the PTM (Primary Thickening Meristem) and the STM (Secondary Thickening Meristem) activity. There are differences in the interpretation of which meristem would be responsible for primary thickening. In Cordyline fruticosa the procambium forms two types of vascular bundles: collateral leaf traces (with proto and metaxylem and proto and metaphloem), and concentric cauline bundles (with metaxylem and metaphloem). The procambium also forms the pericycle, the outermost layer of the vascular cylinder consisting of smaller and less intensely colored cells that are divided irregularly to form new vascular bundles. The pericycle continues the procambial activity, but only produces concentric cauline bundles. It was possible to conclude that the pericycle is responsible for the primary thickening of this species. Further away from the apex, the pericyclic cells undergo periclinal divisions and produce a meristematic layer: the secondary thickening meristem. The analysis of serial sections shows that the pericycle and STM are continuous in this species, and it is clear that the STM originates in the pericycle.The endodermis is acknowledged only as the innermost layer of the cortex.