Ontogenesis of stomata in Velloziaceae: paracytic versus tetracytic?

In Velloziaceae, the number of subsidiary cells has been used to characterize species and support groups. Nevertheless, the homology of the stomatal types have not been scrutinized. Stomatal ontogenesis of Vellozia epidendroides and V. plicata, assigned to have tetracytic stomata, and of V. glauca and Barbacenia riparia, assigned to have paracytic stomata, were investigated. In the four species studied, stomata followed perigenic development. Subsidiary cells arise from oblique divisions of neighbouring cells of the guard mother cell (GMC). These cells are elongated and parallel to the longer axis of the stoma. Polar cells show wide variation, following the shape and size of the epidermal cells in the vicinity. Hence, these cells cannot be called subsidiary cells. This wide variation is due to a much higher density of stomata in some regions of the leaf blade. This distribution of stomata forces the development of short polar cells, leading to an apparently tetracytic stomata. In regions of low concentration of stomata, higher spatial availability between the GMCs allows the elongation of polar cells, leading to evident paracytic stomata. Therefore, the four studied species are considered braquiparacytic, questioning the classification of stomata into tetracytic and paracytic in Velloziaceae.

Diterpenóides com esqueleto cleistantano de Vellozia aff. carunculares martius ex seubert (Velloziaceae)

From the hexane extract of leaves, stem and roots, of Vellozia aff. carunculares, fourteen cleistanthane diterpenoids were detected by HRGC-MS, through the analysis of their fragmentation patterns. Comparison of their MS spectra with those of authentic standards previously isolated from other species of the family Velloziaceae allowed the identification, with a high degree of confidence, of eigth known cleistanthane diterpenoids. Of these, four were isolated and identified from their MS, IR and ¹H and 13C NMR spectra, as the known cleistantha-8,11,13-trien-7-one, cleistantha-8,11,13-trien-3,7-dione, cleistantha-1,8,11,13-tetraen-3,7-dione and the first reported 6-alpha-hydroxy-cleistantha-8,11,13-trien-7-one. The triterpenoid beta-amyrin was also isolated.

Ontogenesis of stomata in Velloziaceae: paracytic versus tetracytic?

In Velloziaceae, the number of subsidiary cells has been used to characterize species and support groups. Nevertheless, the homology of the stomatal types have not been scrutinized. Stomatal ontogenesis of Vellozia epidendroides and V. plicata, assigned to have tetracytic stomata, and of V. glauca and Barbacenia riparia, assigned to have paracytic stomata, were investigated. In the four species studied, stomata followed perigenic development. Subsidiary cells arise from oblique divisions of neighbouring cells of the guard mother cell (GMC). These cells are elongated and parallel to the longer axis of the stoma. Polar cells show wide variation, following the shape and size of the epidermal cells in the vicinity. Hence, these cells cannot be called subsidiary cells. This wide variation is due to a much higher density of stomata in some regions of the leaf blade. This distribution of stomata forces the development of short polar cells, leading to an apparently tetracytic stomata. In regions of low concentration of stomata, higher spatial availability between the GMCs allows the elongation of polar cells, leading to evident paracytic stomata. Therefore, the four studied species are considered braquiparacytic, questioning the classification of stomata into tetracytic and paracytic in Velloziaceae.

HOMOLOGIES OF FLORAL STRUCTURES IN VELLOZIACEAE WITH PARTICULAR REFERENCE TO THE CORONA

New data on floral morphology, development, and vasculature in two Brazilian genera of the monocot family Velloziaceae (Pandanales) are used to explore the homologies of their unusual floral structures, especially the corona of Barbacenia and the corona-like appendages and multiple stamens of some Vellozia species. All Velloziaceae have epigynous flowers. Some species of Vellozia are polyandrous, and stamen number can be variable within species. In Vellozia jolyi, there is a single stamen opposite each sepal and a stamen fascicle (of three secondary stamens) opposite each petal. Each stamen possesses a single vascular bundle, and these are united into a single aggregate bundle in proximal regions of the fascicle. Stamens mature centripetally within each fascicle. The coronal appendages of both genera are closely associated with the stamens, but they share some vasculature with the tepals and develop late in ontogeny. The coronal organs cannot readily be homologized with any of the typical floral organs, but they show partial homology with both tepals and stamens. They are most readily interpreted as a late elaboration of the region between the petals and stamens associated with epigyny and the hypanthium.

Desiccation tolerance in Pleurostima purpurea (Velloziaceae)

Previous works suggested that Pleurostima purpurea (Velloziaceae-Barbacenioideae) shows a remarkable capacity to endure desiccation of its vegetative tissues. P. purpurea occurs in monocotyledons mats on soil islands in the Pao de Acucar (Sugar Loaf) one of the most recognizable rock outcrops of the world, in Rio de Janeiro, southeastern Brazil. Mats of P. purpurea occur in cliffs by the sea some meters above the tidal zone. Although living in rock outcrops almost devoid of any soil cover, P. purpurea seems to occur preferably on less exposed rock faces and slightly shady sites. Usually, less extreme adaptations to drought would be expected in plants with the habitat preference of P. purpurea. Relying on this observation, we argue if a combination of different strategies of dealing with low water availability can be found in P. purpurea as on other desiccation tolerant angiosperms. This study aims to examine the occurrence of desiccation tolerant behavior in P. purpurea together with the expression of drought avoidance mechanisms during dehydration progression. For this, it was analyzed the gas exchanges, leaf pigments and relative leaf water content during desiccation and rehydration of cultivated mature individuals. P. purpurea behaved like typical drought avoiders under moderated drought condition with stomatal closure occurring around a relative leaf water content up to 90%. During this process, it was observed a delay in the leaf relative water content (RWC(leaf)) decrease comparing to the plant-soil relative water content (RWC(plant-soil)). As soil dehydration worsened, gas exchanges restrictions progressed until a lack of activity which characterizes anabiosis. The loss of chlorophyll occurs before the end of total dehydration, characterizing the presence of poikilochlorophylly. The chlorophyll degradation follows the RWC(leaf) decrease, which achieved the minimum average value of 17% without incurring in leaf abscission. The chlorophyll re-synthesis seems to start well after the full rehydration of the leaf. During all of this process, carotenoid content remained stable. These results are coherent with a combination of drought avoidance and desiccation tolerance in P. purpurea which seems to be coherent with the amplitude of water availability in the rock outcrop habitat where it occurs, suggesting that the periods of water availability are sufficiently long for the success of the costly desiccation tolerant behavior but too short to make a typical drought avoider species win the competition for exploring the rock outcrop substrate where P. purpurea occurs.

Five vicarious genera from Gondwana: the Velloziaceae as shown by molecules and morphology

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.

Homologies of floral structures in velloziaceae with particular reference to the corona

New data on floral morphology, development, and vasculature in two Brazilian genera of the monocot family Velloziaceae (Pandanales) are used to explore the homologies of their unusual floral structures, especially the corona of Barbacenia and the corona-like appendages and multiple stamens of some Vellozia species. All Velloziaceae have epigynous flowers. Some species of Vellozia are polyandrous, and stamen number can be variable within species. In Vellozia jolyi, there is a single stamen opposite each sepal and a stamen fascicle (of three secondary stamens) opposite each petal. Each stamen possesses a single vascular bundle, and these are united into a single aggregate bundle in proximal regions of the fascicle. Stamens mature centripetally within each fascicle. The coronal appendages of both genera are closely associated with the stamens, but they share some vasculature with the tepals and develop late in ontogeny. The coronal organs cannot readily be homologized with any of the typical floral organs, but they show partial homology with both tepals and stamens. They are most readily interpreted as a late elaboration of the region between the petals and stamens associated with epigyny and the hypanthium. © 2010 by The University of Chicago. All rights reserved.

GEOGRAPHICAL GENETIC STRUCTURING AND PHENOTYPIC VARIATION IN THE VELLOZIA HIRSUTA (VELLOZIACEAE) OCHLOSPECIES COMPLEX

Premise of the study: Vellozia hirsuta forms a complex presenting wide morphological and anatomical variation, resulting in five specific names and 14 morpho-anatomical patterns occurring in disjunct populations. We carried out a phylogeographical study to investigate the existence of correlation among the genetic and morphological patterns within this complex, and to determine whether it is composed of various species or should be treated as an ochlospecies, a species having widely polymorphic and weakly polytypic complex variation, with morphological characteristics varying independently. Methods: We carried out phylogeographical analyses using cpDNA rpl32F-trnL intergenic region. Key results: We found 20 haplotypes in 23 populations sampled. The populations are genetically structured (Phi(ST) = 0.818) into four phylogeographical groups demonstrating geographical structuring but with no correlation with morpho-anatomical patterns. Our analyses do not support recognizing any of the species now synonymized under Vellozia hirsuta. The northern populations were the most genetically differentiated and could be considered a distinct taxon, as they are also morphologically different. Conclusions: It is recommended that Vellozia hirsuta be considered a single enormously variable species. The patterns of variation within V. hirsuta probably are related to climatic changes that occurred during the Pleistocene Epoch in tropical Brazil when reductions in forest cover favored the expansion of V. hirsuta populations into extensive lowland areas. The expansion of forest cover at the end of the glaciations would have again restricted the occurrence of campos rupestres vegetation to high elevations, which constitute the current centers of diversity of this species.

Novitates Velloziacearum florae phanerogamicae Sancti Pauli

São descritas duas espécies novas de Velloziaceae do norte de São Paulo e áreas adjacentes de Minas Gerais, Vellozia obtecta e V. peripherica. São discutidos suas relações taxonômicas e os caracteres que as sustentam como novas. São fornecidas também descrições anatômicas da lâmina foliar e do pedicelo. A sinonimização de Barbacenia fragrans e B. tricolor sob B. tomentosa é também apresentada e discutida.

Species composition and biogeographic relations of the rock outcrop flora on the high plateau of Itatiaia, SE-Brazil

We studied the flora of vegetation islands on rock outcrops on the Itatiaia Plateau (22°21'S and 44°40'W), at 2,400 m.a.s.l. A total of 114 vascular plant species, which correspond to ca. 20%-25% of the currently inventoried flora of the plateau, were sampled in 197 small vegetation islands (total area of 0.034 ha). Xerophytes and hydrophytes were often found side by side due to environmental heterogeneity at a small scale, explaining in part the high species diversity. Rock outcrops may support floras quite distinct from those in neighbouring habitats, due to the action of strong environmental filters, but in Itatiaia the geographic distribution patterns among rupicolous plants appear to mimic those described for the whole flora around it, with 15.1% of narrow endemic species and six strictly rupicolous plants. Underlining the "temperate" nature of the high elevation climate in Itatiaia, the sampled flora was dominated by species of the families Asteraceae and Poaceae, and the number of CAM (crassulacean acid metabolism) species was very low. A few endemic species of tropical origin - Pleurostima gounelleana (Beauv.) Men. (Velloziaceae) and Fernseea itatiaiae (Wawra) Baker (Bromeliaceae) - play a crucial role in this vegetation, as pioneer mat-formers facilitating later establishment of numerous other species. Hemicryptophytes prevail in the sampled flora, while therophytes are exceptionally rare and mainly consist of opportunistic species associated with disturbances. Numerous microhabitats and strong environmental gradients in these high elevation rock outcrops afford opportunities for establishment of a highly diversified flora. These island-like environments may represent an important refuge for grassland species from fire and other disturbances in the surrounding grasslands.

Floristics, structure and soil of insular vegetation in four quartzite-sandstone outcrops of "Chapada Diamantina", Northeast Brazil

Soil islands on rocky surfaces often harbor aggregated vegetation that consists of insular plant communities. These islands are typical of the rocky outcrops and in various parts of Brazil form the so-called "campos rupestres" vegetation. Four of such sites have been selected in the state of Bahia, Northeast Brazil, for this comparative study on floristics and vegetation structure: three areas situated inside the "Parque Nacional da Chapada Diamantina" (Guiné, Fumaça and "Gerais da Fumaça") and one is at the border of the Environmental Protection Area of "Marimbus-Iraquara" ("Mãe Inácia"). All occurring vegetation islands were studied in four random plots of 10 × 10 m per site. Soil was often shallow, sandy and acidic. Vascular plant species were determined, with respective life forms and canopy coverage areas. The total number of species when all four sites were added was 135, and the number of species per island varied from 2 to 32. The areas of the 214 soil islands varied from 0.015 to 91.9 m², totaling 568 m² in the four sites. Monocotyledon families were dominant, essentially Velloziaceae, as well as Orchidaceae, Bromeliaceae, Amaryllidaceae and Cyperaceae. Among the eudicotyledons, dominant families were mainly Clusiaceae, Asteraceae and Melastomataceae. The biological spectra revealed that phanerophytes and hemicryptophytes predominated among the life forms, while chamaephytes had the largest coverage area. Epilithic and desiccant chamaephytes composed the most conspicuous interspecific associations, and were probably related to early successional processes. Sites closest to one another were not the most similar in structure, indicating that other factors more relevant than distance might be involved in the abundance of species in space.

Comparação da vegetação arbustivo-arbórea de uma área de cerrado rupestre na Chapada dos Veadeiros, Goiás, e áreas de cerrado sentido restrito do Bioma Cerrado

Foram determinadas a composição florística e a estrutura da vegetação arbustivo-arbórea, incluindo monocotiledôneas, em uma comunidade de cerrado rupestre, no município Alto Paraíso de Goiás, Goiás. Os objetivos desse estudo foram: 1. Comparar os aspectos florísticos e estruturais da área estudada com aqueles de outros 14 estudos com comunidades arbustivo-arbóreas, com e sem a presença de monocotiledôneas, 2. Avaliar os padrões fitogeográficos das 15 áreas comparadas. Foram amostradas 71 espécies, sendo cinco espécies de monocotiledôneas (três Velloziaceae e duas Arecaceae). Considerando as monocotiledôneas, a comunidade inventariada foi a mais densa (1.977 indivíduos ha-1) e apresentou a segunda maior área basal (11,25/ m²/ ha-1), entre as áreas comparadas. No entanto, sem as monocotiledôneas a densidade e área basal reduziram para 892 indivíduos ha-1 e 7,55/ m²/ ha-1, respectivamente. Os índices de diversidade (H'/†=/ 2,81) e equabilidade (J'/†=/ 0,66) foram baixos com a presença das monocotiledôneas, mas se elevaram, com a exclusão das espécies desse grupo (H/ =/ 3,63, J'/†=/ 0,86). Os aumentos nos valores de riqueza, densidade e área basal, com a inclusão das monocotiledôneas indicaram elevada importância das famílias Velloziaceae e Arecaceae na comunidade de cerrado rupestre estudada. A flora foi representada predominantemente por espécies de cerrado sentido restrito sobre solos profundos. No entanto, cinco das dez espécies com maiores VI são consideradas habitat especialistas de cerrado rupestre (Vellozia variabilis Mart. ex Schult. f., Wunderlichia cruelsiana Taub., Schwartzia adamantium (Cambess.) Bedell ex Giraldo-Cañas, Hyptis pachyphylla Epling e Vellozia tubiflora (A. Rich.) Kunth). Além do mais, foi observada baixa similaridade florística entre a área de estudo e as áreas comparadas, sugerindo particularidade florística do cerrado rupestre de Alto Paraíso de Goiás. Os padrões fitogeográficos, revelados por análises de agrupamento (UPGMA) e ordenação (DCA), indicaram influência da altitude, da proximidade geográfica entre áreas e de suas localizações em relação aos biomas adjacentes ao Cerrado (Floresta Amazônica, Mata Atlântica e Caatinga).

Foliar cuticular alkanes of Camarea (Malpighiaceae) and their taxonomic significance

Camarea is a South-American endemic genus comprising eight species. In the present work n-alkanes from foliar cuticular waxes of 23 specimens, representing seven species of Camarea were analyzed, aiming at establishing interspecific affinities and evaluating the usefulness of n-alkane distribution as species characteristic. The sampling included also specimens of Peixotoa rericulata and Janusia guaronitica (both Malpighiaceae). The results were used to obtain a phenogram indicating chemical affinities between species. The results are in agreement with morphological similarities among some Camarea species. Intraspecific variability was small, suggesting that n-alkane distribution may be useful for species characterization and establishment of links among Camarea species. The results support the recognition of Camarea triphylla as a synonym of Camarea axillaris and are not coherent with a hybrid condition of a population exhibiting morphological characteristics combining Camarea affinis and Camarea hirsuta, suggesting instead that the individuals analyzed belong either to Camarea hirsuta or a close species. Distribution of n-alkanes is inadequate to distinguish among Malpighiaceae genera: P reticulata has n-alkane distribution similar to several Cumarea species. (C) 2008 Elsevier Ltd. All rights reserved.