Acta Botanica Brasilica
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Open Access journal
ISSN (Print) 0102-3306
Published by SciELO [724 journals]
- Agrobiodiversity and in situ conservation in quilombola home gardens with
different intensities of urbanization
Abstract: ABSTRACT Among the agricultural environments of traditional communities, home gardens are frequently cited as high agrobiodiversity sites. However, the agrobiodiversity of home gardens along a rural-urban gradient demands study in order to identify possible influences of urbanization and to support mitigation of impacts. The present work investigated the role home gardens play in the in situ agrobiodiversity conservation of plants in quilombola communities with different degrees of urbanization. The study found that more urbanized communities have larger home gardens, but the average richness of plant species in these areas was not statistically different among the communities. Furthermore, the abundance of plant species was similar. Medicinal and food plants were mainly found in home gardens of the communities with high to intermediate levels of urbanization, while ornamental plants were more common in rural community home gardens. It is believed that crop exclusivity in home gardens of the more urbanized communities highly influenced the results, increasing the role home gardens play in maintaining traditional practices. The elevated and statistically equal species richness in home gardens suggests that, despite the factors generated by urbanization, all of the communities are very important for in situ conservation of native and introduced species.
- Functional antagonism between nitrogen-fixing leguminous trees and
calcicole-drought-tolerant trees in the Cerrado
Abstract: ABSTRACT The Cerrado is the largest savanna of South America and its physiognomy varies from savanna to woodlands. There are two main types of woodlands in the Cerrado: dystrophic woodlands, dominated by N-fixing leguminous trees (LEG), and mesotrophic woodlands dominated by non-leguminous drought-tolerant trees (DRY), which are calcicoles and sensitive to Al3+. The working hypothesis is that LEG and DRY are functional antagonists in terms of the acidification/alkalization processes involving different forms of inorganic nitrogen and pH, Ca2+ and Al3+ in soil. Tree species basal area and soil properties were used to investigate the antagonism between LEG and DRY using generalized linear models. The results suggest that LEG and DRY are antagonists. The LEG were positively associated with Al3+, NO3- and NH4+ content and negatively related to increasing Ca2+ content, whereas the DRY were negatively associated with Al3+, NO3- and NH4+ and positively associated with increasing Ca2+ content. The upper soil layer in plots dominated by LEG species became more acidic and the upper soil layer in plots dominated by DRY species became more alkaline. The results suggest that LEG and DRY are functional antagonists and their preferences for NH4+ or NO3- might influence the way the Cerrado woodland changes.
- Spore germination, early development and some notes on the effects of in
vitro culture medium on Frullania ericoides (Nees) Mont. (Frullaniaceae,
Abstract: ABSTRACT In bryophytes, establishment can occur by a sexual or asexual process, but the production of spores enables colonization of a wider range of habitats and substrates than can asexual propagules. Successful germination is critical for establishment in a new environment. This paper addresses germination and sporeling development in Frullania ericoides, a leafy liverwort species. Fresh spores were inoculated in vitro in different culture strengths of Knop’s nutrient solution (one-fourth strength, half strength, full strength, one and a half strength and double strength), in order to evaluate the effects of this solution on spore germination and on the development of external protonema. On the first assessment, spore germination was observed at all the concentrations. Germination was endosporic, with cell division and proliferation, resulting in a globular protonema, within the spore wall. Beginning at the fourth week, the development of tightly concave primordial leaves was observed in all but the double-strength medium. Throughout the period of study, the treatments with lower concentrations exhibited external protonema with greater lengths. The double-strength treatment was statistically different from other treatments in at least two parameters. The results of this study demonstrate the potential of in vitro culture techniques for bryophyte spore studies and germplasm preservation.
- Flower and floral trichome morphology of species of Dyckia Schult. f.
(Bromeliaceae, Pitcairnioideae), and their importance to species
characterization and genus taxonomy
Abstract: ABSTRACT This paper presents a morphological analysis of the flower and floral trichomes of three rare species of Dyckia: Dyckia ibicuiensis, D. polyclada and D. racinae. Flowers at anthesis were collected from natural populations and subjected to morphometric and microscopic analysis. Among the most representative features for Dyckia are: morphometrics of individual floral parts; the general configuration of the androecium and gynoecium; the degree of fusion of the stigmatic lobes; the morphology of the ovules, especially in relation to the chalazal appendix; and the presence and constitution of peltate trichomes in the perianth, which exhibited a polymorphism not previously reported for Dyckia. The characters were effective at describing each species, proposing phylogenetic inferences and recognizing infrageneric groupings. We propose two species groups, which are consistent with previous hypotheses about the relationships among the species of the genus. The objective of this study was to provide floral morphological data useful for characterizing these three rare species, delimiting the genus and forming phylogenetic hypotheses.
- The flower anatomy of five species of Myrteae and its contribution to the
taxonomy of Myrtaceae
Abstract: ABSTRACT Considerable effort has been spent towards understanding the phylogeny of Myrteae, and based on the phylogenetic data presently available the traditional subdivision of Myrteae into three subtribes is not supported. The present paper aims to assess the usefulness of floral characters in distinguishing five species that represent five of the six South American clades of Myrteae (Myrtaceae). Floral buds and flowers of Campomanesia adamantium, Eugenia pitanga, Myrceugenia alpigena, Myrcia multiflora and Myrciaria cuspidata were collected from individual plants growing in the Cerrado (Brazilian/Central South American savanna). Among these species, the perianth of E. pitanga is the most distinct due to its vasculurization and pilosity. The hypanthium is thickest in C. adamantium and M. alpigena, while M. delicatula possesses tangentially elongated cells. Anthers do not exhibit much variation among the studied species, while M. alpigena is the only species with trichomes and secretory cavities distributed throughout the mesophyll of the outer wall of the ovary. The ovaries of all of the studied species exhibit vascularization in the form of a single ring of larger-sized bundles. Comparative analysis of these floral structures demonstrates that they are useful in separating these species, and thus the subtribes, of Myrteae.
- Pseudocyphellae ontogeny and thallus anatomy in species of Punctelia Krog
(Parmeliaceae, lichenized Ascomycota)
Abstract: ABSTRACT The genus Punctelia has been traditionally characterized by the type and distribution of pseudocyphellae, medullary chemical substances and the shape of conidia, whereas its species have been distinguished using mainly the shape, location, abundance and size of pseudocyphellae. Given that Punctelia is not monophyletic, additional studies are needed to determine its current delimitation. The present study used conventional techniques for structural studies using optical and scanning electron microscopy in order to describe and compare the structure and ontogeny of the pseudocyphellae of five species of Punctelia. The main differences among the studied species involve the type of pseudocyphellae development, the presence or absence of an epicortex cover and the organization and structure of the upper cortex. In one group of species the pseudocyphellae are formed from the outside to the inside of the thallus; in the other group, pseudocyphellae formation begins with the organization of medullary hyphae into circular groups in specific places. The present study contributes to the understanding of the structure and ontogeny of pseudocyphellae, and to the differentiation and delimitation of lobules and isidia.
- Abiotic environmental conditions for germination and development of
gametophytes of Cyathea phalerata Mart. (Cyatheaceae)
Abstract: ABSTRACT In order to successfully establish themselves in their natural environment, ferns need habitats with abiotic conditions that are suitable for spore germination and gametophyte development. The objective of this study was to assess the influence of abiotic factors on the initial development of Cyathea phalerata cultivated in vitro. Spore germination and gametophyte development were assessed under varying conditions of surface sterilization, pH, temperature and photoperiod. Exogenous contamination was eliminated by sterilizing spores with 2.5 % NaClO for 15 min and sowing them into a culture medium supplemented with nystatin. Spores germinated at all pHs tested. Gametophytic development was faster in acidic pHs. Cultures at 25 °C exhibited the highest percentages of germination and laminar gametophytes. The species produced its highest percentages of gametophytes in cultures with photoperiods between 6 and 18 h. The optimal abiotic conditions found here for in vitro development of C. phalerata are similar to those found in its natural habitat. The southern limit of this species to north of the 30th parallel in Rio Grande do Sul, Brazil, may be because further south spores do not encounter the ideal combined conditions of temperature, pH and photoperiod determined in the laboratory.
- The taxonomic significance of seed morphology in the Passiflora subgenus
Abstract: ABSTRACT The center of diversity for Passiflora subg. Astrophea is in low altitude areas of northern South America. The majority of species of this group are difficult to find in nature. Seed morphology was described in detail for 25 species of Passiflora subgenus Astrophea, a subgenus that until now did not exist. For morphological analysis, 20 seeds per species were measured for length, width and thickness, and the arithmetic means calculated. The seeds varied in length, width and thickness. Eight types of ornamentation were found. The margins varied among crestate, dentate, parted, entire and parted-crestate. The seed apex can be distinguished by the shape and position of the apical appendage. Seed shape varied among obovate, lanceolate, cordiform, and oblong to elliptical. An identification key was developed and a PCA was performed both using the principal morphological characters. Morphological characters of seeds are a new source of data for delimiting taxa with quite conflicting morphological boundaries, such as seen here with the Passiflora subgenus Astrophea. Furthermore, seed morphology is especially useful for the identification of specimens with only fruits and, consequently, seeds available.
- The role of terrestrial bromeliads in determining the spatial organization
of plant life forms in a tropical coastal forest
Abstract: ABSTRACT The interplay between plant-plant interactions and light heterogeneity in the understory of tropical forests has rarely been examined. We aimed to identify the relative importance of the understory light environment and terrestrial bromeliads in explaining the abundance and spatial organization of different plant life forms along a coastal forest gradient from seashore inland in southeastern Brazil. We estimated the abundance of various life forms (herbs, woody plants, bromeliads, climbers, and palms) and the degree of light availability using hemispherical photographs in 165 plots (1 m2) within a 1.75 ha site. We used ordination methods, partial redundancy analysis (pRDA), spatial filtering using Moran’s eigenvector mapping, and Moran’s I splines. Forest cover was highly heterogeneous, but did not explain variation in abundance of life forms. Spatially, bromeliads were negatively associated with woody saplings, herbs and climbing plants at scales between 5-20 m, while the distance to seashore was found to be unrelated to these patterns. Our findings revealed that terrestrial bromeliads play an important role in the spatial organization of various life forms near the forest floor. Overall, the presence of terrestrial bromeliads and the plant area index better explained the understory vegetation than forest cover and distance to seashore.
- Genetic diversity in populations of Maytenus dasyclada (Celastraceae) in
forest reserves and unprotected Araucaria forest remnants
Abstract: ABSTRACT Understanding the genetic structure and diversity of plants is fundamental to their conservation and permits their sustainable use by local communities. The genus Maytenus (Celastraceae) is composed of plants possessing pharmacological and antioxidant properties. However, the genetic and economic properties of the species M. dasyclada, a typical species of Araucaria forests in Brazil and Uruguay, have been little studied. In this work, the genetic structure and diversity of natural populations of M. dasyclada located in unprotected and preserved forest remnants were investigated using RAPD and isozymes markers. The results demonstrated that in areas of preservation, populations of M. dasyclada possess a relatively high degree of polymorphism and high values for Na, Ne, Shannon index, He and Ho, indicating high genetic variability. Moreover, these protected populations are very close to each other and potentially experience significant gene flow. The results presented here highlight the relevance of preservation areas for the conservation of M. dasyclada, and that populations inhabiting these areas could serve as a genetic source for the recovery of populations in regions where genetic diversity has been lost.
- Resupinate Dimorphy, a novel pollination strategy in two-lipped flowers of
Abstract: ABSTRACT This work provides a summary of the typical floral structure of subtribe Hyptidinae (Lamiaceae), in which both style and stamens are declinate within or near the concave anterior corolla lobe. Cross-pollination is facilitated by protandry, acting in conjunction with the explosive release of the stamens and pollen. In contrast, we report that in the three species of the genus Eplingiella we found individuals with either resupinate or non-resupinate flowers, which represents a novel floral dimorphism. In these species of Eplingiella, the style occupies a position towards the posterior corolla lip and opposes the declinate stamens. Thus, in non-resupinate flowers the pollinating bee receives pollen on its ventral side and makes contact with the style on its dorsal side, whereas in resupinate flowers, the bee receives pollen on its dorsal side, and contacts the style on its ventral side. Both floral morphs seem to be required to achieve cross-pollination. In the two populations studied, each of the two morphs is present and in similar proportions, providing a novel means of promoting cross-pollination and reducing selfing. The situation in Eplingiella is compared to some other examples of floral polymorphism, but appears to be a unique pollination strategy, here termed Resupinate Dimorphy.
- Pathways affect vegetation structure and composition in the Atlantic
Forest in southeastern Brazil
Abstract: ABSTRACT Although impacts generated by gaps can affect vegetation, few studies have addressed these impacts in the Atlantic Forest. Our aim was to investigate the effects of pathways of varying widths on vegetation structure and composition, considering dispersal syndromes, diversity, life forms, successional categories and threatened and exotic species occurrence in the Atlantic Forest. We studied three pathways with widths of 2, 10 and 20 m, intersecting a protected area in southeastern Brazil. To assess edge effects, plots were established adjacent to paths (edge) and 35 m from the edge (neighborhood), and in a control area without pathways. Wider pathways (10 and 20 m) exhibited reduced tree height and diameter, high liana density, exotic species, and a high proportion of pioneer and anemochorous species. In conclusion, our results indicate that the vegetation structure of narrow pathways (2 m) is similar to the control area, and that wide linear gaps cause negative effects on vegetation and extend to a distance of at least 35 m into the forest interior. Considering that linear gaps generate permanent effects to vegetation and may affect other organisms, we suggest that these effects must be considered for successful management of protected areas, including planning and impact mitigation.
- Pollen diversity in selected species of the tribe Chironieae (Gentianaceae
Juss.) that occur in the Atlantic Forest, Brazil
Abstract: ABSTRACT Based on molecular data, the tribe Chironieae (Gentianaceae) is divided into three subtribes. This study aims to describe the pollen morphology of representatives of two of the three subtribes that occur in the Atlantic Forest in order to contribute to a better understanding of the palynology of these taxa and to clarify the taxonomy of the family: subtribe Chironiinae (Centaurium erythraea and Zygostigma australe) and subtribe Coutoubeinae (Coutoubea ramosa, C. spicata, Deianira chiquitiana, D. damazioi, D. erubescens, D. nervosa and D. pallescens). Botanical material was obtained from exsicates and treated by acetolysis for light microscopy. Pollen grains were measured and photomicrographed, and the results statistically analyzed. For SEM study, non-acetolyzed pollen grains were sprayed onto metal stubs. The results show that the pollen grains in Chironiinae are medium-sized, prolate-spheroidal or subprolate, 3-colporate, monads, with striate-reticulate ornamentation. In Coutoubeinae the pollen grains are large or medium-sized tetrads with aperture varying between 3-porate or 3-hemicolpates and the sexine microreticulate (D. erubescens) or varied reticulate (the other species). Pollen morphology proved to be an important tool for the systematics of the family since it corroborated the existing placement of species into subtribes based on molecular data.
- Development of carpels and ovules in Dialypetalanthus fuscescens Kuhlm.
(Rubiaceae): an enigmatic taxon
Abstract: ABSTRACT Dialypetalanthus is a monospecific genus that occurs in the Amazon Basin of Brazil, Bolivia and Peru and occupies a controversial position among the Rubiaceae. We continue this taxonomic discussion with the overall aim of clarifying the systematic position of D. fuscescens within the Rubiaceae. To accomplish this, we analyzed the ontogeny of its gynoecium, in particular the floral meristem, as well as the development of the carpels and cauline placentation. Gynosporogenesis and the differentiation of the carpellary septa and ovules were also described. Dialypetalanthus fuscescens was classified according to evolutionary diagrams found in the literature. The following characteristics were observed in D. fuscescens: 1) permanence of the floral meristem in the central basal part of the early flower bud; 2) dual origin of carpellary septum; 3) trizonate ovular primordia with only one fertile gynospore per ovule; and 4) cellular proliferation in the chalazal region. Embryological results confirm the classification of D. fuscescens in the subfamily Ixoroideae. These results are distinct from any others previously proposed in the evolutionary diagram. Therefore, we conclude that this study has presented evidence strongly suggesting that Dialypetalanthus possesses new morphological-type of ovule we refer to as the Dialypetalanthus-type.
- Lectotypes for species of Passiflora L. (Passifloraceae) described by
João Barbosa Rodrigues
Abstract: ABSTRACT During taxonomic review of the Brazilian species of the Passiflora subgenus Astrophea and P. subg Decaloba, six names published by the Brazilian botanist João Barbosa Rodrigues were found in need of discussion: Passiflora alliacea, P. amalocarpa, P. cabedelensis, P. hexagonocarpa, P. hydrophila and Tacsonia coccinea. The original illustrations are here designated as lectotypes for P. alliacea, P. amalocarpa, P. cabedelensis (a synonym of P. amalocarpa), P. hexagonocarpa, P. hydrophila (a synonym of P. costata) and Tacsonia coccinea (a synonym of P. spinosa).
- Cuticular n-alkane in leaves of seven Neotropical species of the family
Lecythidaceae: a contribution to chemotaxonomy
Abstract: ABSTRACT Biosynthesized from very long-chain fatty acid wax precursors, n-alkanes make a valuable contribution to the taxonomy of plants. The alkane components of foliar epicuticles of seven Neotropical species of Lecythidaceae were investigated: Bertholletia excelsa, Cariniana legalis, Couroupita guianensis, Eschweilera alvimii, Eschweilera ovata, Gustavia augusta and Lecythis pisonis. Specimens were collected in the metropolitan area of Recife, Pernambuco, and their n-alkane fractions were analyzed by gas chromatography. The chemical relationships among the species were then evaluated using cophenetic correlation and UPGMA. Among the seven species, a total of 15 n-alkanes, with 21-35 carbon atoms, were identified and formed a consistent group of B. excelsa, C. guianensis, E. ovata, G. augusta, and L. pisonis with n-C31. The greatest similarities were found between B. excelsa and L. pisonis, and between C. guianensis and G. augusta. Nevertheless, a phenetic analysis based on a larger number of species is needed to better understand the chemotaxonomic value of epicuticular n-alkanes within the Lecythidaceae.
- Inter- and intra-population variability in physical dormancy along a
Abstract: ABSTRACT Physical dormancy enables plants that occur in temporally stochastic and harsh environments to survive; thus, within the distribution area of a species, the percentage of seeds with physical dormancy is expected to increase towards more arid and unpredictable areas. There have been no previous studies evaluating both inter and intra-population variability in physical dormancy along a precipitation gradient. The aim of this study was to determine the inter- and intra-population variability in physical dormancy of seeds of Vachellia aroma (Fabaceae) along a precipitation gradient. We collected mature fruits from four localities along a precipitation gradient in central Argentina for an imbibition experiment using controlled germination chambers. Changes in physical dormancy were not found along the precipitation gradient; however, a trend toward higher percentage of seed imbibition (lower PY) at the most humid extreme of the gradient was observed. On the contrary, we did observed intra-population variability in three of the four populations, suggesting that most of the populations of V. aroma might have the ability to deal with the environmental variability encountered at local scale. This study highlights the importance of studying both inter- and intra-population variability in physical dormancy.
- A holoparasitic plant severely reduces the vegetative and reproductive
performance of its host plant in the Caatinga, a Brazilian seasonally dry
Abstract: ABSTRACT Host-parasite interactions between plants may reduce the vegetative and reproductive performance of the host plant. Although it is well established that parasitic plants may negatively affect the metabolism and the number of vegetative/reproductive structures of their hosts, the effects of this interaction on the reproductive characteristics of the host plant are poorly understood. Here we document the interaction between Cuscuta partita (Convolvulaceae) and its main host, Zornia diphylla (Fabaceae), in the Caatinga of northeastern Brazil. We measured diverse reproductive/vegetative attributes of Z. diphylla in 60 plots randomly distributed in patches that were parasitized and not parasitized by C. partita. Both vegetative and reproductive attributes, such as the number of branches, leaves and flowers, and the individual biomass of Z. diphylla were significantly reduced by the parasitism. The number of pollen grains and ovules per flower were not affected by the parasitism, but since the parasitism reduced flower production, the total number of pollen and ovules per individual and population may also be reduced. Additionally, pollen viability was significantly reduced in the flowers of parasitized individuals. We conclude that C. partita may negatively impact the vegetative and reproductive performance of its main host, Z. diphylla in distinct ways in the Caatinga.