Scielo RSS <![CDATA[Acta Botanica Brasilica]]> vol. 30 num. 2 lang. en <![CDATA[SciELO Logo]]> <![CDATA[Seasonal variation in allelopathic potential of the leaves of <strong><em>Copaifera langsdorffii</em></strong> Desf.]]> ABSTRACT The deciduous plant Copaifera langsdorffii contains important medicinal compounds which may also be allelopathic and inhibitory to plant growth. The species is endemic to the Brazilian Cerrado where there is pronounced climatic seasonality. In this study we demonstrate the allelopathic capacity of extracts from the leaves of C. langsdorffii and pre-purified fractions of the extract. Analysis by HPLC-PAD-ESI-MS confirmed the presence of quercetin-3-O-α-rhamnoside and kaempferol-3-O-α-rhamnoside as major components, as well as phenolic acid derivatives of gallic acid. The extracts from samples collected during the wet season were rich in flavonoids and reduced the seed germination rate, root emergence time, and root growth of Sorghum bicolor seedlings. Leaves of C. langsdorffii collected in both the wet and the dry season did not differ in the overall phytotoxic potential of their extracts, but differences detected in tested subfractions seem to indicate subtle seasonal changes in chemical composition. These results indicate that changes in the seasonal water status of the Cerrado induces differential synthesis of compounds with higher allelopathic activity. <![CDATA[Improving collection efforts to avoid loss of biodiversity: lessons from comprehensive sampling of lycophytes and ferns in the subtropical Atlantic Forest]]> ABSTRACT Estimating species richness with herbarium data and new collections allows us to understand the distribution of diversity. We investigated the accuracy of lycophyte and fern sampling along a vegetation gradient in the subtropical Atlantic Forest in southern Brazil. We compiled lycophyte and fern collection metadata and estimated species richness and assessed sampling accuracy for sixty 50 x 50 km units using ACE, Chao 1, Chao 2, Jackknife 1 and Jackknife 2 estimators. We compiled data for 12,779 fern specimens of 441 species, 67 of which were sampled in only one unit (singletons) and 35 in two units (duplicates). Of the 60 units examined, only 11 had observed values that were above 70% of their estimated values, and 14 had observed levels between 65-70% of the estimated values, meaning that 35 units had a sampling accuracy of less than 65%. In spite of the long history of lycophyte and fern collecting in the study area, there remain units with a lower than expected sampling accuracy for a subtropical forest. This finding indicates that a sizeable collection effort is needed in order to discover the actual distribution of species before the effects of fragmentation and deforestation become permanent. <![CDATA[Reproductive phenology, seed removal and early regeneration in relation to distance from parental plants of a native palm in small Atlantic forest fragments]]> ABSTRACT The Brazilian Atlantic Forest is a global biodiversity hotspot, but most of what remains are small fragments. Small fragments are often harsh environments for forest plant recruitment due to edge effects and the loss of frugivorous animals that provide seed dispersal. We recorded the one-year reproductive phenology of the keystone palm Syagrus romanzoffiana in small (&lt;2.5ha) Atlantic Forest fragments in southeastern Brazil. We tested the Janzen-Connell hypothesis with seed-removal experiments and followed the five-year survival of recruits in relation to the distance from parental plants. Palms produced many fruits throughout the year (mean 2,600/plant). More seedlings were found away from parental plants than near them, thereby supporting the Janzen-Connell hypothesis. Almost 45% of seedlings alive in 2010 were dead five years later, but recruitment of new seedlings compensated for this mortality. Distance-dependent factors influenced the density of early ontogenetic stages, but had limited effects on juveniles or on seed removal. High seed production, seed dispersal provided by disturbance-tolerant frugivores and the relatively long-term survival of adults, seedlings and juveniles seem to allow the persistence of S. romanzoffiana in the forest fragments, but possibly at the cost of an increased clumped distribution and reduced gene flow at the landscape scale. <![CDATA[More than environmental control at local scales: do spatial processes play an important role in floristic variation in subtropical forests?]]> ABSTRACT The effect of environmental variables on the plant species distribution in the Atlantic Forest raises the interest of researchers, but few studies, mainly at local scales, analyzed the influence of spatial factors on the environment and species distribution. Linear models and spatial correlograms were used to evaluate whether environment and space may predict variations in species composition of trees and shrubs in a Subtropical Rainforest remnant. The study area was divided in 25 plots of 400 m², systematically distributed, where individuals with DBH ≥ 5 cm were measured. Elevation and slope were the most important predictors of the floristic variations, but space, generally neglected in researches on South American's vegetation, had a relevant influence, as a structural component, in terms of environmental variables, and as intrinsic biological component, here probably as result of constraints in species dispersion. Although the origin of great part of the variation in species composition remained unknown, which is common in studies on vegetation, results indicated, for the first time, the complex role of spatial and environmental variables in the composition of trees and shrub species in a Subtropical Rainforest of Brazil. <![CDATA[Ethnobotany of babassu palm ( <strong><em>Attalea speciosa</em></strong> Mart.) in the Tucuruí Lake Protected Areas Mosaic - eastern Amazon]]> ABSTRACT Documenting the ethnobotanical knowledge of populations living in protected areas is important both for science and for the effective conservation of these areas, as it can help to clarify the level of dependency that human communities have on local plant resources. Babassu (Attalea speciosa, Arecaceae) is one of the most important non-timber forest resources of rural communities in the Amazon. We explored the ethnobotanical knowledge and uses of babassu by riverine populations inhabiting the Tucuruí Lake Protected Areas Mosaic in the eastern Amazon, by examining the diversity, purposes and descriptions of its uses and aspects of its extraction. Data were collected in 2010 and 2014 from 193 families. A total of 1,226 use records were cited representing 60 different uses. Records were classified into nine use-categories; utensils and tools was the most important category, followed by construction and human food. The use with the greatest purpose consensus value among the informants was thatch. Babassu proved to be an important resource for the livelihood of the local communities in providing shelter, food and reliable energy. Most informants lacked knowledge about sustainable practices and management of this resource. <![CDATA[A study of the morphoanatomical characters of the leaves of <strong><em>Chamaecrista</em></strong> (L.) Moench sect. <strong><em>Apoucouita</em></strong> (Leguminosae-Caesalpinioideae)]]> ABSTRACT Little attention has been paid to species of Chamaecrista sect. Apoucouita (Leguminosae-Caesalpinioideae), especially regarding anatomical studies. When only vegetative material is available, the identification of such species may be difficult. Additionally, vegetative material of some species of C. sect. Apoucouita may be even harder to identify because they can resemble species of Inga Mill. (Leguminosae-Mimosoideae). The present study focused on recognizing morphoanatomical characters of leaves that are taxonomically useful for the species of C. sect. Apoucouita by employing standard anatomical techniques. The arrangement of the vascular system in the petiole/rachis, dorsiventral mesophyll, mucilage idioblasts in the epidermis of leaflets and hypostomatic leaves were some of the characters shared by all species studied. Length of the petiole, position and type of extrafloral nectaries, leaflet venation, presence and type of papillae on the epidermis of the leaflet blades and sclereids in the mesophyll were some of the characters useful in the distinction of taxa. The vascular arrangement of the petiole/rachis is a promising character in the distinction of species of C. sect. Apoucouita and Inga. Based on morphoanatomical data, the taxonomic revision of some species and varieties ascribed to C. sect. Apoucouita is suggested. <![CDATA[The necessity of management in a lake of the Atlantic Forest biodiversity hotspot: nitrogen levels connected to a persistent bloom of <strong><em>Cylindrospermopsis raciborskii</em></strong>]]> ABSTRACT Conservational studies of the threatened Atlantic Forest biome are frequently restricted to terrestrial ecosystems. We know little about the water bodies, specially considering that this biome covers the third largest system of lakes in Brazil. Some of these lakes are located inside the protected "Rio Doce State Park", but many others are found outside this reserve. These external lakes are seldom studied, but understanding their response to human activities is essential for the conservation and the protection of the lakes inside the Park. We evaluated the effects of degradation in a lake outside the Park, which shows a constant bloom of the toxic invasive cyanobacteria Cylindrospermopsis raciborskii. Phytoplankton, climate and physico-chemical variables were assessed from 2011 to 2013 to evaluate which were the major determinants of the lake dynamics. Despite the seasonal changes, the lake was always eutrophic, and cyanobacteria, transparency and nutrients were the major indicators of water characteristics. The lake seems to be nitrogen-limited and cyanobacteria were negatively correlated with nitrogen levels, since the constantly dominant C. raciborskii is a superior competitor for N. We suggest that the monitoring of nitrogen levels is fundamental to establish management strategies to avoid harmful algae blooms in this Atlantic Forest lake. <![CDATA[Morpho-physiological responses of a subtropical strain of <strong><em>Cylindrospermopsis raciborskii</em></strong> (Cyanobacteria) to different light intensities]]> ABSTRACT The toxigenic cyanobacterium Cylindrospermopsis raciborskii previously restricted to tropical latitudes, has been increasingly reported in temperate lakes in recent decades. The causes of its biogeographical expansion are under investigation, but efficient physiological adaptation to changes in temperature and light regimes are likely to be involved. The present study evaluated the morpho-physiological responses of a strain of C. raciborskii from southern Brazil to nine light intensities, from 9 to 250 µmol photons m-2 s-1. Blooms of this cyanobacterium are regularly recorded in the region. Morpho-physiological responses were measured based on growth rate and trichome length. Cylindrospermopsis raciborskii showed slow growth at low light intensities, 9 and 20 µmol photons m-2 s-1, and responded morphologically by increasing the length of trichomes. In turn, the strain displayed constant maximum growth rates at light intensities higher than 50 µmol photons m-2 s-1. These results support the hypothesis that C. raciborskii can survive under low light conditions and continue to produce viable trichomes. Moreover, the strain achieved high growth rates under a relatively wide range of light intensities, a physiological adaptation that can potentially be a competitive advantage in the phytoplankton community. <![CDATA[Distribution patterns of ferns and lycophytes in the Coastal Region of the state of Rio Grande do Sul, Brazil]]> ABSTRACT A survey of ferns and lycophytes of the Coastal Region of the state of Rio Grande do Sul (CRRS) was performed based on field work and collections of the main regional herbaria. The following were evaluated for each species: preferential habits (terrestrial, epiphytic or aquatic), geographic distribution patterns and habitats (forest, grassland, and wetland). The occurrence of a latitudinal gradient in diversity was tested over five latitudinal ranges using the Sørensen Similarity Index. A total of 17 lycophyte and 206 fern species representing 28 families was found between the latitudes of 29° and 34°S. Exclusively terrestrial species were predominant (162), with the majority (113) exhibiting wide Neotropical distributions, followed by species that also occurred in the state of Paraná (44). The forest habitat harbored the greatest number of species (159), while grasslands had the fewest (26). Cluster analysis showed pronounced floristic differentiation among latitudinal Ranges III (31°01' to 32°S) and IV (32°01' to 31°S), with a similarity index of only 0.41. Our results demonstrate a strong north-to-south reduction in species richness in the study area, which is related to environmental conditions along the latitudinal gradient and, especially, microclimatic differences in the transition zone between the Atlantic Forest and Pampa biomes. <![CDATA[Survey of bryophytes in Serra da Canastra National Park, Minas Gerais, Brazil]]> ABSTRACT Serra da Canastra National Park is located in southwestern Minas Gerais State and contains several phytophysiognomies of the Brazilian Cerrado. To date, no study on bryophytes has been conducted in this area and the present study is the first to be carried out in this major biological reserve of Cerrado located on the Brazilian Plateau. This study found 289 species of bryophytes, including mosses, liverworts, and one species of hornwort, representing fourty-one Brazilian endemic species and 56 new records for Minas Gerais State. Most species are widely distributed in Brazil, with only 16% having restricted distributions. Regarding worldwide distribution, 31% are Neotropical. Lejeuneaceae had the highest species richness among liverwort families with 53 species, whereas Sphagnaceae had the highest richness among moss families with 26 species. Phaeoceros laevis was the only hornwort species found in the park. This study contributes to the understanding of bryophyte species richness and distribution, and provides the worldwide and Brazilian distribution of the bryophyte flora of Serra da Canastra National Park, an important center for biodiversity conservation. <![CDATA[Notes on <em>Junghuhnia</em> (Agaricomycetes) in Brazil]]> ABSTRACT Junghuhnia is a cosmopolitan genus of Agaricomycetes (Basidiomycota), mostly characterized by having a dimitic hyphal system and encrusted cystidia. The genus comprises 37 legitimate species, eight of which have been reported in Brazil. This study provides updated information about the diversity and distribution of Junghuhnia in Brazil by reporting J. semisupiniformis for the first time from South America, J. globospora from Brazil, J. carneola from northeastern Brazil and the state of Pará, J. nitida from the state of Pernambuco, and J. subundata from the state of Amazonas. Descriptions of J. semisupiniformis and J. globosbora, as well a key to the accepted species of Junghuhnia from Brazil, are provided. <![CDATA[Evolution of seed dispersal in the Cerrado biome: ecological and phylogenetic considerations]]> ABSTRACT The investigation of the phylogeny of a group of organisms has the potential to identify ecological and evolutionary processes that have been occurring within a community. Seed dispersal is a key process in the life cycle of vegetation and reflects different reproductive strategies of plants to a set of ecological and evolutionary factors. Knowing the dispersal syndromes and fruits types of a plant community may help elucidate plant-animal interactions and colonization strategies of plants. We investigated dispersal syndromes and fruit types in Cerrado formations as a parameter for understanding the evolution of angiosperm reproductive strategies in this mega-diverse tropical biome. To do this we identified and mapped the distribution of different parameters associated with seed dispersal on a phylogeny of Cerrado angiosperms genera and tested the presence of phylogenetic signal. The results showed that there were strong relationships between fruit types, seed dispersal strategies and vegetation life forms and that these traits were closely related to angiosperms phylogeny and, together, contribute to the evolution of plants in the forest, savanna and grassland formations of the Cerrado biome. <![CDATA[<em>Borreria apodiensis</em> (Rubiaceae: Spermacoceae), a new species from Ceará and Rio Grande do Norte, Brazil]]> ABSTRACT A new species of Borreria (Rubiaceae) from Chapada do Apodi in northeastern Brazil is described and illustrated. A distribution map, illustrations, a conservation assessment, a key to morphologically similar taxa and images of the seeds and pollen grains are provided. <![CDATA[Using ecological niche models to predict the impact of global climate change on the geographical distribution and productivity of <em>Euterpe oleracea</em> Mart. (Arecaceae) in the Amazon]]> ABSTRACT We assess the impact of climate change on the geographic distribution and productivity of Euterpe oleracea (Arecaceae), commonly called açaí. To construct the ecological niche model of E. oleracea, we used 95 points of occurrence, five bioclimatic variables in current and future climate scenarios and Maxent software. The Akaike Information Criteria (AIC) was used to rank the ability of the models (considering ecological, socioeconomic and spatial variables) to explain the variation in productivity of E. oleracea among 200 municipalities. The maps showed that regions with higher environmental suitability for E. oleracea were concentrated in northern and northeastern Brazil, which was similar to the spatial pattern of productivity data of E. oleracea. Future climate conditions tend to promote an increase in the geographical distribution of this species, even though the new regions are in the arch of Amazon deforestation. Only space and the environmental suitability (indicated by the ecological niche model) were important for explaining the productivity of E. oleracea. That is, municipalities that are more productive are located in more suitable environmental regions. Therefore, it is important to use niche models to explain demographic changes and to estimate species demographic attributes. <![CDATA[Leaf phenotypic variation and developmental instability in relation to different light regimes]]> ABSTRACT For pioneer plants, shaded habitats represent a stressful condition, where sunlight exposure is below the optimum level and so leaves expand in order to intercept a greater amount of light. We investigated changes in both phenotypic variation and stress of Bauhinia brevipes in sunny and shaded microhabitats. Leaf area was used as a measure of phenotypic variation, whereas leaf asymmetry (difference between right and left sides of leaves), was used as a measure of stress. We hypothesized an increase in leaf area and stress in shaded locations, which might indicate that B. brevipes was compensating for low light absorption, and elevated levels of stress, respectively. Plants in the sun fitted a fluctuating asymmetry pattern (normal distribution of right minus left sides), while shaded plants were clearly antisymmetric (bimodal distribution of leaf side differences). Leaf asymmetry and area were 5% and 26.8% higher in plants in the shade compared to plants in the sun, respectively. These results were expected since B. brevipes is found predominantly in open areas; so sunlight exposure is important for its development. The presence of antisymmetry is rare in studies of developmental instability, and here it might indicate higher stress compared to plants with fluctuating asymmetry. <![CDATA[Occurrence of homobaric and heterobaric leaves in two forest types of southern Brazil]]> ABSTRACT In ombrophilous forests, light stratification provokes different adjustments by plants for better use of the environmental conditions of each stratum. Among the morphological traits that vary with strata, the presence of bundle sheath extensions (BSEs) is related to water transport, photosynthesis, and leaf mechanical support and classifies leaves as homobaric or heterobaric. This study analyzed the proportion of these types of leaves in a Lowland Ombrophilous Dense Forest (LLODF) and a Mixed Ombrophilous Forest (MOF), and among the strata of each forest type. The morphological leaf traits of 89 LLODF tree species and 57 MOF tree species were examined. The proportion of homobaric and heterobaric leaves did not differ between forests. However, in both forest types, the distribution of species with heterobaric or homobaric leaves depended on strata, with heterobaric species occurring mainly in higher strata, and homobaric species in lower strata. Thus, light stratification acts as an ecological filter on the composition of the vegetation of these forests, favoring heterobaric species in places with higher light intensity and temperature, such as the highest strata of canopy. On the other hand, homobaric species are more frequent in lower strata, where light is less available and humidity higher. <![CDATA[The reproductive biology of the early-divergent genus <strong><em>Anaxagorea</em></strong> (Annonaceae), and its significance for the evolutionary development of the family]]> ABSTRACT Data of six studied Neotropical Anaxagorea species are analyzed and discussed with respect to the population structure, flowering phenology, flower morphology, anthesis, scent emission, thermogenesis, floral visitors, breeding system, fruit-set and seed dispersal. The probably reason for the patchy distribution of small populations of Anaxagorea species within lowland tropical forests is given. A novel explanation of the functional significance of ruminate endosperm is presented. Flowering of the species follows either the annual or the continuous flowering pattern. All studied species have diurnal, two-day lasting, protogynous anthesis; several species have thermogenic flowers. Self-compatibility appears to be the prevailing reproductive system in the genus. However, there is a strong tendency for effecting cross-pollination. Floral scent of Anaxagorea species contains fruit-like components, and the pollinators, primarily Nitidulidae (Colopterus spp.) are attracted by deceit. Strong scenting pollination chambers occur also in most other cantharophilous Annonaceae. Novel floral developments are apparent mainly in fly-, cockroach- and bee-pollinated Annonaceae, which have patterns different from cantharophilous species and exhibit open flowers with reflexed petals, which allow their pollinators to reach and touch the reproductive organs. <![CDATA[Bicarpellate gynoecium in two species of <em>Senna</em> (Fabaceae, Caesalpinioidae, Cassiinae)]]> ABSTRACT Flowers of species of Senna are very morphologically diverse, however, nothing has been reported regarding variation in the presence of a unicarpellate gynoecium, which is characteristic of the group. This study reports the occurrence of a bicarpellate gynoecium in two enantiostylous species of Senna in an area of dry forest (Caatinga) in NE Brazil. Observations of floral morphology and estimates of the proportions of floral morphs in the populations were performed. The species produce three floral types: left (L), right (R) and bicarpellate (B). The proportion of these floral morphs were similar in the populations of Senna macranthera var. micans, but the number of B flowers in populations of S. trachypus was lower than that recorded for L and R flowers. The occurrence of this morphological variation may be related to enhancing pollen capture in both species; in S. trachypus, this variation may also be related to reducing florivory by caterpillars that were observed eating sexual elements of the flowers.