Scielo RSS <![CDATA[Acta Botanica Brasilica]]> vol. 29 num. 4 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[Epiphytic microlichens as indicators of phytosociological differentiation between Caatinga and Brejos de Altitude]]> The present study tested the hypothesis that species richness and composition of epiphytic microlichens can be used to support the phytosociological differentiation between Caatinga and Brejos de Altitude, as exemplified by the Muralha Reserve (Caatinga) and the Parque Estadual Mata do Pau Ferro (Brejo de Altitude), in the state of Paraíba, Brazil. A total of 755 lichen samples were collected, comprising 18 families, 42 genera and 111 species of epiphytic, corticolous microlichens. Overall species richness was higher in the Caatinga, with 67 species, compared to the Brejo, with 46 species. Species richness per sample was significantly higher in the Caatinga compared to the Brejo. Taxonomic composition also differed significantly between the two areas, with Arthoniaceae, Caliciaceae, Chrysothrichaceae, Graphidaceae (particularly Graphis), Lecanoraceae, Mycoporaceae, Pertusariaceae, and Trypetheliaceae being dominant in, or exclusive to, the Caatinga, whereas Coenogoniaceae, Graphidaceae (Diorygma, Fissurina, Myriotrema, Ocellularia, Phaeographis, Sarcographa), Malmideaceae, Porinaceae and Strigulaceae were dominant in, or exclusive to, the Brejo. Five new species were discovered as result of this study. This is the first study to quantitatively compare richness and community patterns of epiphytic microlichens between two major biomes in Northeastern Brazil, and the first detailed lichen study in the state of Paraíba. <![CDATA[Combined effects of low light and water stress on Jatropha curcas L. promotes shoot growth and morphological adjustment]]> Jatropha curcas (physic nut) is a plant with economic and pharmaceutical uses. Basic studies on the influence of environmental factors on the early development of J. curcas are important for improving farming techniques and increasing productivity. This study investigated the adjustments of J. curcas to the environmental factors of drought and light stress in order to determine which factors most strongly affect the allocation of biomass during early growth. Leaves, stems, and roots of young plants were sampled and leaf area was measured during January and June in 2011. Plants of J. curcas that were grown in shade and subjected to water stress showed higher biomass allocation to aerial parts (mainly stems), which can be explained as a strategy for maximizing carbon assimilation. The pattern of biomass allocation between aerial components and the root system changed in plants grown in shade. During June 2011, biomass in shade-grown J. curcas was preferentially allocated to stems, indicating long-term adjustment. The lower biomass allocation to the root system suggests reduced exploitation of soil water even when this resource is scarce. Thus, over the long term, growth of J. curcas may be compromised by the combined effects of light stress and water deficit. <![CDATA[Key factors affecting seed germination of <em>Copaifera langsdorffii</em>, a Neotropical tree]]> In natural conditions biotic and abiotic factors interact, synergistically affecting seed germination. In this study, we experimentally simulated natural conditions that occur during seed dispersal that can affect the germination of Copaifera langsdorffii. Specifically we evaluated the effect of aril removal by different dispersal agents (birds and ants) and fire on germination. The seeds were submitted to the following treatments: Control (seeds placed to germinate with aril intact); Acid (simulation of passage through the digestive tract of a bird); Aril removal (simulation of aril removed by ants); Fire (seeds exposed to fire). Germination percentage and time varied among treatments (X²=89.735, P&lt;0.001; X²=16.225, P&lt;0.001, respectively). None of the control seeds (intact aril) germinated. Treatments that simulated dispersal (Acid, Aril removal) did not differ in germination percentage, with about 50% of the seeds germinating, however, the acid treatment accelerated seed germination. Fire also had a positive effect on seed germination with about 80% of the seeds germinating. Our results demonstrate the importance of dispersal agents to the population dynamics of C. langsdorffii. Furthermore, the capacity of seeds of C. langsdorffii to tolerate high temperatures is an important attribute for the occurrence of this species in the Cerrado. <![CDATA[Anatomical and morphological modifications in response to flooding by six Cerrado tree species]]> Wetlands are common in the Cerrado (Brazilian savannas) biome, however flooding of these wetlands impairs growth and development of most plants. We evaluated flood tolerance of typical Cerrado trees. Seedlings of Aspidosperma macrocarpon (Apocynaceae), Tabebuia rosea (Bignoniaceae), Handroanthus chrysotrichus (Bignoniaceae), Myracrodruon urundeuva (Anacardiaceae), Kielmeyera coriacea (Calophyllaceae) and Copaifera langsdorffii (Fabaceae) were flooded up to the stem base for 30 days. Stems with cortical cracks, secondary aerenchyma and hypertrophic lenticels were observed in flooded plants of M. urundeuva,H. chrysotrichus and T. rosea while adventitious roots were formed in flooded plants of T. rosea and H. chrysotrichus. However, only T. rosea developed aerenchyma in the root cortex. K. coriacea and A. macrocarpon were the most sensitive to flooding, showing a decrease in survival and necrosis of the leaves and roots. C. langsdorffii and M. urundeuva were less sensitive to flooding, although reductions in root biomass and symptoms of necrosis of the roots were noticeable in flooded seedlings. Flooded M. urundeuva seedlings also had a decrease in total leaf area, leaf biomass, total biomass and in stem growth. Flooding affected root development and reduced stem growth of H. chrysotrichus with symptoms of necrosis of the leaves and roots. T. rosea was the only species where symptoms of injury from flooding were not evident. <![CDATA[How to construct and use a simple device to prevent the formation of precipitates when using Sudan Black B for histology]]> The present work aims to demonstrate the stages of fabrication and use of a simple device to avoid the formation or fixation of precipitates from Sudan Black B solution on tissues. The device consists of four coverslip fragments attached to a histology slide, which serve as points of support for the histological slide under analysis. To work properly, the histology slide with the sections should be placed with the sections facing downwards the device. A small space between the device and the histology slide is thereby created by the height of the coverslip fragments. When Sudan Black B is applied, the solution is maintained within the edges of the device and evaporation is minimized by the small space, thereby reducing the consequent formation of precipitates. Furthermore, by placing the sections facing downward the device, any sporadically formed precipitates are prevented from settling on and fixing to the sectioned tissues or organs. By avoiding the formation of precipitates, plant cells, tissues and organs can be better observed, diagnosed and photomicrographically recorded. <![CDATA[Lycophytes and ferns composition of Atlantic Forest conservation units in western Paraná with comparisons to other areas in southern Brazil]]> This study surveyed lycophyte and fern species in four forest fragments in western Paraná, Brazil, and compared them to 15 other fragments with different plant formations from the Atlantic Forest biome in southern Brazil. In total, five lycophyte species (in two families and two genera) and 98 species and two varieties of ferns (in 16 families and 38 genera) were registered in the four fragments. The most represented families were Pteridaceae (23 spp.), Polypodiaceae (18 spp.), Aspleniaceae (13 spp.), and Thelypteridaceae (11 spp.). Asplenium (12 spp.), Thelypteris (10 spp.), and Blechnum (seven spp.) were among the most represented genera. The occurrence of Dicksonia sellowiana was noteworthy because it was associated with seasonal semideciduous forest and is threatened in Brazil. Similarity among areas was determined by a cluster analysis (UPGMA and Sørensen’s index) and the relation between similarity and geographic distance was determined through Matel’s analysis. The analyses revealed greater similarity among the four study areas and, for these areas as a whole, greater similarity to fragments in Rio Grande do Sul, which is evidence that these areas have similar environmental conditions. <![CDATA[Island effect on diversity, abundance and vegetation structure in the Chocó Region]]> The aim of this study was to evaluate the effect of island area and isolation on species richness and abundance, and vegetation structure of Isla Palma by comparing these parameters with those of the continental location, Playa Chucheros. By sampling vegetation at each locality using Gentry transects (10 50x2 m) we found 204 species of plants at Playa Chucheros, and 103 on Isla Palma. Species richness and abundance of woody plants was higher for Playa Chucheros (472 individuals) compared to Isla Palma (349 individuals). Richness estimators indicate that the plant species richness of Playa Chucheros is almost twice as high as that of Isla Palma. Rarefaction curves suggest that Playa Chucheros had a significantly greater richness than Isla Palma. Furthermore, physiognomic parameters were higher for Playa Chucheros than those observed for Isla Palma, showing that the former supports tree vegetation with higher DBH and greater height. These results indicate that the size and isolation of the island is reflected in a diminished richness and vegetation structure, which can be of significant assistance in the development of better conservation strategies for plants and other groups of organisms on islands. <![CDATA[Somatic embryogenesis in <em>Acrocomia aculeata</em> Jacq. (Lodd.) ex Mart using the thin cell layer technique]]> Considering the necessity of Acrocomia aculeata propagation for large-scale production, the aim of this study was to establish a somatic embryogenesis protocol using the thin cell layer (TCL) technique. Aerial parts of in vitro plants were transversally cut at the base into eight TCLs and placed in a culture medium for callus induction. The induction medium was composed of Y3 salts and Morel´s vitamins and supplemented with 150, 300 or 600 μM picloram. After 12 weeks the calli were transferred to a medium supplemented with BAP or 2-iP (12.5 or 25 μM). After 18 weeks, the somatic embryo clusters were transferred to a conversion medium (plant growth regulator-free medium). Primary callus induction rate was higher in the first three TCLs and in media containing 150 or 300 µM picloram. The best maturation results were obtained in medium containing 12.5 μM 2-iP or 12.5 μM BAP. Few somatic embryos converted into plants. The histological analyses showed that callus induction started adjacent to vascular bundles after two days of culture, and somatic embryos arose in the periphery of nodular calli. This study showed that the TCL embryogenesis protocol is promising for in vitro multiplication of A. aculeata. <![CDATA[Establishment of post-harvest early-developmental categories for viability maintenance of <em>Araucaria angustifolia</em> seeds]]> Araucaria angustifolia seeds are recalcitrant, and their metabolism remains high during storage. This research aimed to describe the initiation of germination in A. angustifolia seeds during storage in order to standardize the assessment of physiological quality and to promote seed conservation. Seeds were collected from two populations and stored for 270 days in the natural laboratory environment and cold chamber. Seeds were classified according to four early developmental stages: I - mature seeds; II - seeds with elongation along the embryonic axis; III - beginning of root protrusion; IV - advanced germination stage, with seedling shoots. After categorization, physical and physiological quality was assessed. In freshly collected seeds, only category I was observed. At 270 days, approximately 40% of seeds were in category III in laboratory conditions, while the maintenance in a cold chamber delayed germinative metabolism. Viability tests showed that seeds in categories III and IV were more susceptible to damage caused by storage. In conclusion, the percentage of viable A. angustifolia seeds depends on the development stage after collection. Seeds that have reached early developmental category III should be prioritized for propagation, while those remaining in categories I and II should be longer stored with periodic assessment for reduction in physiological quality. <![CDATA[First report of modern pollen deposition in moss polsters in a semiarid area of Bahia, Brazil]]> Recent studies have shown that pollen analyses of natural substrates can produce data valuable for understanding the local pollen productivity and dispersal, deposition, and preservation potential of pollen grains. In this study, we aimed to acquire novel information about the dynamics and preservation of pollen in Caatinga environment through the palynological study of moss polsters. Samples of moss polsters in soil (MPS) and on rock (MPR) were collected from the Canudos Biological Station in the Bahia State (Brazil) and subjected to standard chemical treatments for the extraction of pollen residues. In total, 372 pollen types were recorded from the samples of which the taxonomical affinity of 140 was determined. The most represented families were Fabaceae (23 pollen types/16.42%) and Asteraceae (12 pollen types/8.57%). The MPS samples had a higher pollen concentration (21,042.04 pollen grains/cm²) than the MPR samples (7,829.35 pollen grains/cm²). On the other hand, the MPR samples had a greater diversity (68.26% of the identified pollen types). Qualitative analysis showed that the plants of shrub and subshrub habits had the greatest representation among the pollen types (35.0%). Overall, moss polsters proved to be excellent natural air pollen collectors in Caatinga environment, provided they had moist microhabitats for their development. <![CDATA[The seed bank of subtropical grasslands with contrasting land-use history in southern Brazil]]> The expansion of land use for agriculture is among the main reasons for the reduction of natural grasslands around the world, and little is known about the recovery potential of original native grassland vegetation from seed banks. The aim of this study was to assess the seed bank potential of grassland areas with or without history of cultivation in southern Brazil. Specifically, we aimed at evaluating if agricultural use allowed for the persistence of species typical of natural grasslands in soil seed banks. We analyzed seed banks in two areas with a history of cultivation and in two natural grasslands. Samples were collected in spring and autumn in order to assess transient and persistent components, and were characterized by density, richness, presence of exotic species and relationship between seed bank and established vegetation. Both richness and density were high; we found a total of 114 species and a mean density of 61,796 seedlings/m2 for all four areas in the spring sampling. In the natural grasslands, the dominant species of established vegetation were mostly absent from the soil seed bank. Our study indicates that the seed bank is of little relevance for the recovery of typical grassland vegetation after disturbance. <![CDATA[Flavonoid profiling and nodulation of some legumes in response to the allelopathic stress of <em>Sonchus oleraceus</em> L.]]> Annual sowthistle (Sonchus oleraceus) has been reported to produce allelopathic effects. Two greenhouse experiments were conducted to estimate the allelopathic potential of both plant residue and root exudates of S. oleraceus on flavonoid composition and nodulation in a leguminous crop, Trifolium alexandrinum, and in two leguminous weeds, Melilotus indicus and T. resupinatum. The results of high performance liquid chromatography-mass spectrometry (HPLC-MS/MS) showed that all three legumes contained six flavonoid aglycones: apigenin, daidzein, kaempferol, luteolin, myricetin and quercetin; and seven flavonoid glycosides: daidzin, genistin, hesperidin, hyperoside, kaempferol-7-O-glucoside, naringin and rutin. In general, both plant residue and root exudates had inhibitory effects on the flavonoid composition and nodulation of the target species. However, residue of S. oleraceus caused a significant increase in both individual and total detected flavonoids in T. alexandrinum. The results suggest that the phytotoxins released from S. oleraceus may restrain the biosynthesis of flavonoids in the target species, whereas the accumulated flavonoids in T. alexandrinum are allelopathic-induced metabolites and suggest a resistance mode in this crop. <![CDATA[Environmental severity promotes phylogenetic clustering in <em>campo rupestre</em> vegetation]]> The stress-dominance hypothesis postulates that the importance of competition in plant communities declines with increasing environmental stress while the importance of environmental filters increases. To test this hypothesis for campo rupestre vegetation, we analyzed phylogenetic diversity and community structure of angiosperm communities at two study sites within the Itacolomi State Park, Minas Gerais, Brazil. Plots representing more favorable habitats, such as those with a higher percentage of rocky outcrops that might permit the tapping of deeper water and nutrient resources as well as higher contents of clay and loam thereby increasing water and nutrient availability, show higher phylogenetic diversity and therefore lower phylogenetic clustering than plots with more sever habitats. This observation is consistent with the stress-dominance hypothesis if we assume ecological niches to be conserved within evolutionary niches. However, more comprehensive studies including tests for phylogenetic signal of ecological niches are necessary before generalizations for larger regions may be carried out. <![CDATA[Characterization of seed germination and protocorm development of <em>Cyrtopodium glutiniferum</em> (Orchidaceae) promoted by mycorrhizal fungi <em>Epulorhiza</em> spp.]]> Cyrtopodium glutiniferum is an endemic orchid of Brazil with potential medicinal and ornamental applications. As mycorrhizal fungi are essential for the initiation of the orchid life cycle, the aim of this study was to determine the strains of mycorrhizal fungi suitable for seed germination and protocorm development of C. glutiniferum and to characterize the symbiotic development of protocorms. Seeds of C. glutiniferum were inoculated with nine mycorrhizal fungi, Epulorhiza spp., Ceratorhiza spp., Rhizoctonia sp., originally isolated from Brazilian neotropical orchids. Only Epulorhiza isolates promoted seed germination and protocorm development. Three Epulorhiza isolates (M1, M6 = E. epiphytica, M20 = Epulorhiza sp.) promoted protocorm development until leaf production at 63 days. The protocorms are comprised of parenchyma cells delimited by a unistratified epidermis; the parenchyma cells of the upper part of the protocorms are smaller than those located more towards the base. Intact and digested pelotons were observed inside of protocorms implying that the seedlings were capable of mycotrophy. Additionally, the development of a bud primordium only occurred after colonization by fungus. This study suggests that C. glutiniferum has a preference for strains of Epulorhiza and that fungus digestion is essential to protocorm development. <![CDATA[Taxonomic value of histochemical features of the style in early lineages of Asteraceae]]> In this paper we examine lipophilic substances, tannins, proteins, reducing carbohydrates, starch, and oxalate salts in early lineages of Asteraceae to test if they are a useful complement to classification studies. Styles of mature flowers of 44 species were processed according to plant histochemical techniques and observed by means of a light microscope. Lipophilic compounds were always present in the cuticle and cell walls, and in some species were located inside the cells. Proteins were located in the style cell walls and cell interior of most of the analyzed species. No tannins were found. In general, there is a correlation in the presence of reducing sugars and proteins. Starch granules and oxalate salts were found in the style parenchyma of a few species. Cytoplasmic content of lipophilic compounds, proteins, and reducing sugars predominates in Barnadesioideae and Nassauvieae (Mutisioideae), and histochemical similarities were found among members of Gochnatioideae <![CDATA[Pollen morphology and its taxonomic significance in the genus <em>Bomarea</em> Mirb. (Alstroemeriaceae) - II. Subgenus <em>Bomarea</em>]]> Pollen morphology of 52 species (out of c. 79) of the Bomarea subgenus Bomarea was examined using light microscopy and scanning electron microscopy (SEM), or using SEM alone. The studied species of Bomarea were stenopalynous, characterized by large, oblate, monosulcate monads with reticulate exine sculpture in most species. Wide variation was observed in quantitative palynological features. The studied taxa were divided into four major groups based on exine ornamentation observed under SEM: microreticulate, reticulate, coarsely rugulate, and psilate-perforate. The reticulate exine sculpture may be a plesiomorphic character state for the genus Bomarea, and the coarsely rugulate and finely rugulate-perforate or psilate-perforate exine sculptures may have evolved independently more than once. In agglomerative hierarchical clustering (AHC) analyses of the genus Bomarea using quantitative pollen data, the studied species were distributed in either two (similarity-based) or four (dissimilarity-based) major clusters. Neither the recent molecular phylogenetic analyses nor the AHC analyses of Bomarea have recovered clades/clusters that represent traditionally recognized subgeneric taxa for the genus. Therefore, the most reliable infrageneric classification of Bomarea can be achieved by combining morphological, palynological, and molecular data from more extentive sampling of all the species. <![CDATA[Alpha and beta diversity of phytoplankton in two subtropical eutrophic streams in southern Brazil]]> This paper reports the alpha and beta diversity of phytoplankton communities of two streams differing in land use. We analyzed which environmental conditions affect diversity of the phytoplankton communities and tested the hypothesis that stream stretches protected by forests will have lower species richness, whereas higher beta-diversity would occur among the non-protected stretches. Samples were taken quarterly, from February to November 2012, in nine stretches, including four non-protected stretches, two partially protected stretches and three totally forest-protected stretches. Eleven abiotic variables and their coefficients of variation were analyzed. Phytoplankton was analyzed for species richness (alpha diversity), frequency of occurrence and beta-diversity. Species richness was calculated by first and second order jackknife indexes. Biotic data were submitted to Sørensen similarity analysis. A total of 429 infrageneric taxa were reported, representing 88% of the estimated expected species richness. The phytoplankton composition was typical for lotic environments with high richness values of Bacillariophyceae (66.0%). High phytoplankton richness values occurred in all the sampled stretches, even though beta-diversity was moderate and indicated similarity between the sampled stretches, therefore only a part of the original hypothesis was corroborated. <![CDATA[Ecological aspects of <em>Langsdorffia hypogaea</em> (Balanophoraceae) parasitism in the Pantanal wetlands]]> Most studies on holoparasitic plants have focused on taxonomic or systematic issues. The objective of this study was to examine the ecological aspects of parasitism of Langsdorffia hypogaea (Balanophoraceae) in the Pantanal wetlands. Individuals of L. hypogaea were dug out by hand and the host trees were identified. Eighty-eight percent of host trees exhibited zoochory dispersal syndrome. Protium heptaphyllum and Cordiera sessilis represented 50% of the sampled trees. Both species are evergreen and are preferentially shade-tolerant species growing under the canopy of other trees. Fecal sample of collared peccaries (Pecari tajacu) had seeds from both the host tree (Protium sp.) and the parasite L. hypogaea. We therefore propose the hypothesis that P. tajacu play a role as a seed disperser and may affect root parasitism.