Scielo RSS <![CDATA[Acta Botanica Brasilica]]> vol. 28 num. 4 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b><i>In vitro</i> propagation of <i>Anathallis adenochila</i> (Loefgr.) F. Barros (Orchidaceae), a species endemic to southern and southeastern Brazil</b>]]> Anathallis adenochila is a small epiphytic orchid, endemic to the Atlantic Forest in the southern and southeastern regions of Brazil. Information on the species is scarce and limited to distribution and occurrence data, with no reports about its development. In the present study, plantlets were propagated in vitro, and the influence of different concentrations of macronutrient salts and sucrose on the survival and development of the species was assessed. The analysis were performed on complete Murashige and Skoog (MS) medium and half MS medium (with half-strength macronutrients) containing 10, 30 or 60 g L-1 of sucrose. Plantlet survival, height of the aerial part, and the length of the longest root were significantly greater on half MS medium containing 30 or 60 g L-1 of sucrose. The number of leaves per plantlet was higher in the presence of 60 g L-1 of sucrose, regardless of macronutrient concentration, and the highest number of roots was observed in plantlets cultured on half MS medium with 60 g L-1 of sucrose. This first report of Anathallis adenochila in vitro propagation may contribute to future studies on the physiological and ecological aspects of the life cycle of this species. <![CDATA[<b>Effects of chemical treatments and environmental factors on seed dormancy and germination of shepherd's purse (<i>Capsella bursa-pastoris</i> (L.) Medic.)</b>]]> Shepherd's purse (Capsella bursa-pastoris) is a problematic weed in citrus orchards and crop fields in northern Iran. In a series of laboratory and greenhouse experiments, we evaluated the effects that treatment with gibberellic acid (GA3) and potassium nitrate (KNO3), as well as environmental factors, including temperature, the duration of pre-chilling (wet and dry), drought stress, salt stress, pH, and sowing depth, have on seed dormancy breaking and germination in C. bursa-pastoris. Treatment with GA3 strongly stimulated germination of C. bursa-pastoris in conditions of light/dark and continuous darkness. The germination rate was highest (40.08%) for seeds treated with 400 ppm of GA3 in the light/dark condition. Treatment with KNO3 did not significantly influence seed germination. Longer wet pre-chilling promoted germination and was more successful in seed dormancy breaking than was dry pre-chilling. Seed germination occurred at 10-30ºC and within a range of pH of 3-11. Drought and salt stress both strongly inhibited germination. Seedling emergence decreased in proportion to sowing depth. The rates of C. bursa-pastoris germination and seedling emergence were highest for seeds on the soil surface. <![CDATA[<b>Plant functional groups</b>: <b>scientometric analysis focused on removal experimentsPlant functional groups: scientometric analysis focused on removal experiments</b>]]> Understanding what determines species co-occurrence and its consequences for ecosystem functioning is central to the study of plant ecology. The ecological similarity of species can explain co-occurrence patterns, species interactions, and how species affect ecosystem processes. A useful approach to answer these questions is to group similar species in functional groups and then perform removal experiments. Here, we conducted a scientometric review of articles about plant functional diversity and plant functional group removal. We identified publication patterns and impact; environmental and geographic gaps; ecological effects being tested; which groups are removed; and what the removal methods are. We analyzed articles published between 1991 and 2012 in journals indexed for the Thomson ISI Web of Science database. Although the number of articles and citations of experimental articles increased during that period, the corresponding increase for functional diversity articles was 12 times greater. This might be because field and cafeteria experiments are harder to conduct. Most studies were performed in temperate regions, where taxonomic knowledge and scientific investment is greater. Studies on herbaceous vegetation predominate, probably because short-lived species are more easily removed and manipulated than are trees. The main reason for the removal experiments was to test hypotheses related to competition, and clipping at ground level was the most common removal method. Few studies were performed in the field and in greenhouses, which could control for differential responses of natural conditions and controlled environments. <![CDATA[<b>Seasonality and mycorrhizal colonization in three species of epiphytic orchids in southeast Mexico</b>]]> Orchids establish symbiosis with Rhizoctonia mycorrhizal fungi, forming the characteristic pelotons within the cells of the root cortex. Under natural conditions, terrestrial and epiphytic orchids have different levels of dependence upon the fungal symbiont, although various authors have mentioned that once orchid plants reach maturity the interaction becomes weaker and intermittent. Recent evidence shows that in some epiphytic orchid species mycorrhization is constant and systematic. In three species of wild orchids from southeast Mexico, we show that mycorrhization is systematically present in roots of different ages, in the wet and dry seasons. We demonstrate that the volume of the root that is colonized depends upon the quantity of rainfall and the diameter of the root, and that rainfall also determines the presence of fresh, undigested pelotons. In very thin roots, mycorrhizal colonization occupies a considerable proportion of the cortex, whereas in thicker roots the proportion of the volume of the root cortex colonized is lower. <![CDATA[<b>Woody vegetation dynamics in a floodplain<i> campo de murundus</i> in central Brazil</b>]]> Campos de murundus (grasslands dotted with knolls that are covered with savanna-like woody vegetation) are a common landscape in central Brazil. In this study, we assessed for the first time the dynamics of the vegetation in a floodplain campo de murundus, describing changes in composition and structure of the woody vegetation. In 2005, we established 16 permanent 25 × 25 m plots, where we identified and mapped individuals with a trunk diameter at the base ≥ 2.86 cm, as well as measuring the height of those individuals. In 2008 (after two fire events), we resampled the plots. In 2005, we had registered 4.54 m² ha-1 of basal area, 430 individuals, 42 species, 36 genera and 24 families. In 2008, we found an increase in basal area (to 4.65 m² ha-1) and a decrease in numbers of individuals (to 399), species (to 41), genera (to 35) and families (to 23). Species diversity did not differ between the two surveys. Mortality exceeded recruitment (2.68% year-1 vs. 1.29% year-1). Nevertheless, the community showed a gain in basal area owing to the growth of surviving individuals and, particularly, to the rise in the number of basal sprouts. We argue that the small floristic turnover may be related to the great resilience of the woody vegetation, whereas the structural changes might reflect the effects of the burnings in the area. <![CDATA[<b>Richness of Marchantiophyta and Bryophyta in a protected area of the Brazilian Amazon</b>]]> The bryophytes of Gurupi Biological Reserve represent an important component of the biodiversity of the Amazon in the Brazilian state of Maranhão. This study aimed to investigate the richness of bryophytes (Marchantiophyta and Bryophyta) from Gurupi Biological Reserve and compare it with that found in other surveys conducted in Maranhão and in the northeastern part of the state of Pará, because the latter shows similarities with the study area in terms of vegetation, geography, demography, and history of occupation. We recorded 983 occurrences of bryophytes (549 Marchantiophyta and 434 Bryophyta) corresponding to 62 species (43 liverworts and 19 mosses), 39 genera, and 12 families. Of those 62 species, 25 have previously been collected from all regions of Brazil, two are restricted to two regions, and four are restricted to the northern (Amazon) region. The bryophyte species identified within the reserve correspond to 28.9% of the known bryophytes in Maranhão and 31.3% of the known bryophytes in northeastern Pará, the reserve therefore more closely resembling the latter area. The exclusively Amazonian elements found in the reserve underscore their affinity for this biome and their presence in the state of Maranhão. The importance of this conservation area to Maranhão and to the Amazon region of the state is confirmed by the high number of new records for the state (41 species), five of which are also new records for northeastern Brazil. <![CDATA[<b>A catalog of Bryophyta types deposited at the National Museum of Brazil</b>]]> While visiting the Herbarium of the Botany Department of the National Museum of the Federal University of Rio de Janeiro (code, R), we located the types of 219 bryophyte names, most of which were published by Karl Müller (cited as Müller Hallensis), whose holotypes were lost during the bombing of the Berlin Herbarium in 1943. A total of 181 names (82%) are possible candidates for lectotypification and most likely not to be found elsewhere. We also found the complete collection of Müller's "Bryologia Serrae Itatiaiae", made by Ernst Ule. <![CDATA[<b>Optimal culture conditions for the initial development of <i>Ilex paraguariensis</i> A.St.-Hil. explants</b>]]> In the state of Rio Grande do Sul, Brazil, yerba mate (Ilex paraguariensis A. St.-Hil.) is an economically and culturally important species. Because of the difficulty in obtaining plantlets from seeds, micropropagation has emerged as an alternative that could increase production. This work aimed to evaluate the effect that treatment with 6-benzyladenine (BA), at concentrations of 2.2, 8.9, and 20 µM and associated with naphthaleneacetic acid (NAA, 0.5 µM), has on the in vitro growth and leaf emission of I. paraguariensis nodal segments cultivated in 0.5 X Murashige and Skoog (MS) medium or 0.5 X Woody Plant Medium (WPM). The most efficient treatment was MS medium with 8.9 µM BA+NAA, in which I. paraguariensis presented greater shoot elongation and higher leaf counts than in the other treatments. Therefore, use of the MS medium with 8.9 µM BA+NAA is recommended in order to increase efficiency in the initial development of I. paraguariensis explants. <![CDATA[<b>The effects of an exotic palm on a native palm during the first demographic stages</b>: <b>contributions to ecological management</b>]]> Biological invasions have negative impacts on native biota and consequently on biodiversity. In patches of Atlantic Forest in Brazil, the Australian palm tree Archontophoenix cunninghamiana has become invasive, whereas the endemic palm Euterpe edulis is threatened with extinction. The two species occupy parts of the same functional niche within the forests, which raises a question: Does the invasive species interfere with the recruitment of the native one when the two co-occur? We compared the initial demographic stages of these palms, and assumed that A. cunninghamiana would present better performance (higher rates of germination and seed viability) and would feature allelopathic properties that could influence the recruitment of the native species. We investigated indirect and direct allelopathic interference, respectively, by watering E. edulis seeds with aqueous leachate solutions of A. cunninghamiana fruits and leaves and by conducting combined germination experiments. The leachate solutions neither inhibited germination nor affected the size of E. edulis seedlings. In the direct interference experiments, depulped A. cunninghamiana seeds had higher viability and germination rates than did E. edulis seeds. In E. edulis, exposure to A. cunninghamiana seeds did not affect germination nor seedling development but slightly decreased germination speed. In conclusion, A. cunninghamiana presented no significant allelopathic impediment to E. edulis establishment. However, because A. cunninghamiana seeds are usually depulped when dispersed by birds, the potential of the species to establish itself in the community surpasses that of E. edulis. We propose management strategies to enhance E. edulis performance and to restrict the spread of A. cunninghamiana. <![CDATA[<b>Poaceae communities in the savannas of the Amazon Estuary in Brazil</b>]]> We sought to identify the major environmental factors that affect the diversity and distribution of Poaceae in the savannas of the Amazon Estuary. The study was conducted across seven areas of savanna in the Amazon Estuary, within which 160 subplots of 1 m² each were established within four 10 × 100 m plots. Soil samples were collected at a depth of 0-20 cm. A total of 24 Poaceae species were recorded. Only two were common to all of the areas studied (Axonopus aureus P. Beauv. and Anthaenantia lanata (Kunth) Benth). The edaphic factors that most influenced the Poaceae in the savannas studied were organic matter, coarse sand, and silt contents. Conversely, rainfall had no effect. The floristic and structural characteristics of the savannas studied suggest that Poaceae communities exhibit low diversity and a peculiar distribution pattern in which a group of species predominate in a given stretch, creating a homogeneous physiognomy. Our findings suggest that the structure of these communities is related to a gradient of soil texture, the percentage of Axonopus and Trachypogon coverage increasing and decreasing, respectively, along that gradient. These data can contribute to the understanding of plant-soil interactions in this environment, promoting strategies for conservation, management, and revegetation. <![CDATA[<b>Structure and floristic diversity of remnant semideciduous forest under varying levels of disturbance</b>]]> The perturbation of Neotropical forests generates large disturbances in biological communities. The species that suffer least from the resulting habitat fragmentation are the pioneers, because they possess greater ability to inhabit disturbed environments. Therefore, it is expected that species diversity will be greater in areas subjected to intermediate disturbance, such as the opening of gaps, because a large number of pioneer species will develop and coexist with species of more advanced successional stages. This study aimed to compare two forest remnants that differed in size and disturbance intensity, in order to determine the effects of disturbances on species diversity and the size ratios of individual trees. This was accomplished with comparative analyses of diversity, richness and diameter ratios obtained for 10 plots at two semideciduous forest sites. We recorded a total of 85 species, of which 70 were in the private nature reserve Fazenda Santa Maria, 58 were in Iguaçu National Park, and 43 were at both sites. Diversity was greater in the more disturbed remaining forest, because this area showed higher species richness, which is in accordance with some premises of the intermediate disturbance theory. There was also an increase in the number of pioneer individuals, and the less disturbed area showed individuals with larger diameters, which is likely attributable to the removal of large individuals from the more disturbed area during the anthropogenic process of forest modification. <![CDATA[<b>Host specificity and experimental assessment of the early establishment of the mistletoe <i>Phoradendron</i> <i>crassifolium</i> (Pohl ex DC.) Eichler (Santalaceae) in a fragment of Atlantic Forest in southeast Brazil</b>]]> Mistletoe establishment relies heavily on a seed reaching a proper host plant. Small frugivorous birds usually disperse large numbers of mistletoe seeds. However, in the field, mistletoes are absent from some potential available hosts. We investigated whether the mistletoe Phoradendron crassifolium has some preferences for specific host trees in a fragment of Atlantic Forest in southeast Brazil. We surveyed 397 tree individuals of 50 species within 25 families. Seven of those species (14%) bore P. crassifolium infections. Although prevalence at the individual level was low (11.6%), there were marked deviations in infection levels among species and families. Most (87%) of the infections (40 of 46) occurred in species belonging to the families Anacardiaceae (Lithraea molleoides and Tapirira guianensis) and Siparunaceae (Siparuna guianensis), which nevertheless accounted for only 26% of the potential individual hosts (103 of 397). We also performed an experiment simulating bird behavior. We inoculated 480 mistletoe seeds to the bark of four potential hosts in field, following the fate of the seeds for five months. No differences in host preference were observed. The low specificity detected at the local level was confirmed by a survey of exsiccata collected over the geographical distribution of the mistletoe, suggesting that P. crassifolium prevalence is more dependent on dispersal limitation than on mistletoe-host compatibility. <![CDATA[<b>Comparative leaf anatomy and morphology of some Brazilian species of <i>Crotalaria</i> L. (Leguminosae: Papilionoideae: Crotalarieae)</b>]]> Anatomical characters often provide strong taxonomic evidence and many times help define species whose morphological limits are in question. This study aimed to survey characters of the leaf anatomy of 16 species of Crotalaria L. occurring mostly in the cerrado (savanna) of central Brazil and in areas of restinga (coastal woodland, or sandy forest) along the coast of the country, in order to improve the current taxonomic circumscription of sections and species. Leaf samples were collected in the field and obtained from herbarium specimens. Standard techniques in plant anatomy were employed, including analyses under light and scanning electron microscopy. Many of the characters analyzed are relatively uniform, but some are diagnostic for species. At the section level, only trichomes with a base composed of radially distributed cells proved useful in the diagnosis of C. sect. Calycinae. The other characters analyzed showed interspecific variation, but no diagnostic value for recognition of the sections. At the species level, unlike the results found for sections, various characters have diagnostic value. Among the characters with diagnostic value at the species level, those related to texture, the venation pattern (such as the formation of areolas and insertion of the ribs secondary to midrib), and, in particular, the epidermis, showed potential for aiding the circumscription of some species. <![CDATA[<b>Galling insects are bioindicators of environmental quality in a Conservation Unit</b>]]> Galls are well distributed across the World and among plant families. Their diversity can support the status of conservation of an area as an urban park, once inventories are presented. These inventories also help to understand the morphological patterns of the galls, based on their most common shape, color, host botanical families, inducers and galled organs. This study is about an inventory of galls at Parque Estadual Serra Verde, Brazil. This conservation unit is an urban park strongly anthropized in a transition area of Cerrado and Mata Atlântica. Galls from four different trails were observed, and collected monthly during one year. The terminology morphospecies was used to distinguish the galls because the identification of the inducers were not always possible. Seventy five morphospecies of galls belonging to 43 host plant species of 24 botanical families were observed. Mostly of the galls was induced by Diptera:Cecidomyiidae, in Fabaceae and Myrtaceae. The most common traits were the globoid shape and green color. The leaves were the most frequent galled organ and followed by the stems. All these tendencies had been already observed in other inventories. Comparing current results with other studies at similar areas, we can assume that the Parque Estadual Serra Verde is very important for conservation. Urban green areas are subject to high disturbance and degradation but also increase the quality of life for the population inhabiting the areas nearby. The diversity of galls at Parque Estadual Serra Verde reflects an area with high levels of stress but with moderate botanical diversity. These features make this protected area an important site for the continuous conservation and regeneration, and highlight the environmental value of Parque Estadual Serra Verde. <![CDATA[<b>Does nutrient cycling differ between fragments of Atlantic Forest with distinct structural aspects?</b> <b>A case study in the state of Rio de Janeiro, Brazil</b>]]> In this study, we evaluate litter biomass and nutrient inputs, as well as nutrient use efficiency (NUE), in two fragments of dense montane rain forest within the Atlantic Forest Biome in the northern region of the state of Rio de Janeiro, Brazil. The total annual average litter production for the two fragments (designated M1 and M2) was 7.72 and 7.56 t ha−¹ year−¹, respectively. The annual nutrient return rate was 146.67, 4.84, 21.41, 64.93, and 17.25 kg ha−¹ year−¹ for N, P, K, Ca, and Mg, respectively. No differences in NUE were observed between the studied fragments, except for that of P. The average NUE for N, P, K, Ca, and Mg, respectively, was 51, 1426, 367, 111, and 428 in fragment M1, compared with 51, 1890, 360, 126, and 472 in fragment M2. The litter biomass input did not differ between the forest fragments studied, indicating that the differences in elevation and forest biomass did not affect nutrient cycling. However, a difference in the litter deposition rate between the dry and rainy periods was observed in fragment M2. <![CDATA[<b>Demography of the endangered tree species <i>Ocotea porosa</i> (Lauraceae) along a gradient of forest disturbance in southern Brazil</b>]]> Ocotea porosa (Ness) Barroso (Lauraceae), a typical tree of the southern Atlantic Forest in Brazil, was heavily exploited for timber in the last century. With the aim of examining the status of the remaining populations, we surveyed five forest fragments in the state of Paraná, in southern Brazil, and evaluated whether disturbances caused by selective logging and fragmentation were related to population structure of O. porosa. We assessed demographic aspects related to tree density, size hierarchy and individual allometry, correlating those parameters with fragment structure variables (fragment size, isolation and logging level). We found that, although all populations occurred in low densities (60-440 individuals ha−¹), the number of adults was significantly lower in the smaller and most disturbed fragments (13 and 35 individuals ha−¹, respectively). We did not detect changes in allometric relationships among individuals in the five populations studied. However, we found that populations in more heavily disturbed areas presented lower size hierarchy (i.e., less dominance of larger trees) than did those in undisturbed areas, suggesting that selective logging affects the population structure of O. porosa, possibly affecting the rates of reproduction and fecundity, which may ultimately increase the probability of local extinction. <![CDATA[<b>Small and hard seeds</b>: <b>a practical and inexpensive method to improve embedding techniques for light microscopy</b>]]> The traditional techniques employed for embedding plant samples are not suitable for the proper processing of small seeds with hard seed coats. Usually, these seeds are broken off from blocks during microtomy, which limits the technical success of this procedure. In this study, Melastomataceae seeds of 101 species were treated prior to embedding in historesin according to three treatments: (1) control, using the standard procedure; (2) fixation and subsequent softening with Franklin solution, glycerin and heating in a water bath; and (3) softening with Franklin solution and subsequent fixation (glycerin and heating in a water bath were also included). For Melastomataceae species, the second treatment provides the best results, and we were able to produce very good sections of the entire seed. Small hard seeds, similar to those found in Melastomataceae, are better embedded when they are softened after subjected to fixation. A combination of softening techniques is necessary to improve the embedding process and to obtain high-quality sections of the embedded samples. In this study, we established a practical, slightly toxic and inexpensive methodology to ensure good preparations for light microscopy that can be applied to a wide range of subjects related to seed science. <![CDATA[<b>Impact of invasion by molasses grass (<i>Melinis minutiflora</i>P. Beauv.) on native species and on fires in areas of <i>campo-cerrado</i> in Brazil</b>]]> In the Cerrado Biome of Brazil, African grasses constitute a serious problem, occurring in virtually all protected areas. Molasses grass (Melinis minutiflora P. Beauv.) accumulates more biomass than do most other species of the herbaceous stratum vegetation native to the Cerrado. In this study, our aim was to determine the impact of M. minutiflora on native vegetation, as well as (using simulations of fire traits) on the characteristics of fires, in invaded areas of the Serra do Rola-Moça State Park (Parque Estadual da Serra do Rola-Moça, PESRM), a protected area where fires are frequent, in the state of Minas Gerais, Brazil. Our main results are that M. minutiflora considerably increases the amount of biomass, becoming the main combustible plant in the campo-cerrado (grassy-woody savanna) fires in the PESRM; that the native monocot biomass is inversely correlated with the M. minutiflora biomass, suggesting suppression of the native herbaceous stratum; that eudicots are diminished by M. minutiflora, both in number of individuals and number of species; and that fires are more severe in M. minutiflora-invaded areas. <![CDATA[<b>First pollen survey of <i>murundus</i> in the Chapada Diamantina region of the state of Bahia, Brazil</b>]]> This was a pollen survey, in which we analyzed the sediments and moss polsters of murundus (termite mounds) in the Chapada Diamantina region of the state of Bahia, Brazil. Palynological treatment revealed the presence of 53 pollen types in murundus sediments, of which 23 were related to plants in the semi-arid zone and 30 remained unidentified. In moss polster samples, the pollen assemblage comprised 42 pollen types for which taxonomic affinities were identified and 54 for which they were not. In our comparison of the two pollen assemblages, we found that moss polsters and murundu sediments shared 15 pollen types. For some of the pollen grains in the murundus sediments, it was not possible to make reliable interpretations because of small number of grains and the poor state of conservation. In contrast, the pollen analyses of the moss polster samples showed that they could represent a useful tool for studies of pollen rain. To our knowledge, this is the first study of murundus as natural pollen collectors. Our findings suggest new possibilities for the use of the pollen records preserved in termite mounds. <![CDATA[<b>Descriptions of <i>Cottoniella fusiformis, Branchioglossum</i>cf.<i> minutum</i> and <i>Frikkiella searlesii</i> (Rhodophyta, Ceramiales) from the Brazilian continental shelf</b>]]> The diversity and distribution of marine macroalgae along the Brazilian coast have been investigated in detail. However, information about the deep-water macroalgal flora remains scarce, available mostly in scattered publications or gray literature. In this context, the aim of this study was to describe three specimens of Rhodophyta (Cottoniella fusiformis, Frikkiella searlesii and Branchioglossum cf. minutum) collected in the deep waters of the continental shelf off the coast of the state of Espírito Santo during expeditions of the program Evaluating the Potential of Living Resources in the Exclusive Economic Zone. The morphology and distribution of the collected species are detailed, and the taxonomic and biogeographic implications are discussed. <![CDATA[<b>Carbon dioxide-enriched atmosphere enhances biomass accumulation and meristem production in the pioneer shrub <i>Baccharis dracunculifolia</i> (Asteraceae)</b>]]> The increase in atmospheric CO2 concentration predicted to the end of this century may cause several alterations on plant species development, which shall result in changes in the structure and function of plant communities. The present work aimed to investigate the effects of the increase in atmospheric CO2 concentration on the development of Baccharis dracunculifolia, a key pioneer Neotropical shrub. Seedlings of B. dracunculifolia were exposed to 720 ppm of CO2 as well as to ambient concentration of CO2 (approximately 360 ppm) during 120 days in open top chambers. Growth and dry biomass accumulation were higher under elevated CO2 concentrations. As a response to CO2 enrichment, there was an increase of 134% in total dry mass, 208% in root dry mass and 152% in stem dry mass. The shrubby habit of B. dracunculifolia and the larger number of meristems produced under high CO2 promoted the increase in 137% in the number of branches. The present study contributes to the knowledge about how pioneer tropical plants may respond to increased atmospheric [CO2] in environments with low nutrient limitation. <link></link> <description/> </item> </channel> </rss> <!--transformed by PHP 04:10:46 21-10-2018-->