Scielo RSS <![CDATA[Acta Botanica Brasilica]]> vol. 29 num. 3 lang. <![CDATA[SciELO Logo]]> <link></link> <description>ABSTRACTStudies that evaluate the physiological and biochemical mechanisms of germination within forest species are needed in order to improve our understanding of such processes. Mercury and dithiothreitol are indicated as important tools in studies that assess the activity of aquaporins during imbibition and germination of seeds. To investigate the alterations caused by mercury inPlathymenia reticulata seedsdifferent doses of mercury were used in the presence and absence of dithiothreitol. Mercury had a dose-dependent effect on the seeds; in the most dilute solutions mercury partially inhibited the imbibition process, whereas in the most concentrated solutions it caused the death of the embryos. A delay in the hydration of the seeds may have caused decreased germination as a result of the reduced functionality of the aquaporins that were oxidized by mercury. In the presence of the reducing agent dithiothreitol, the activity of these proteins was restored and the germination process was re-established. These findings indicate the importance of aquaporins in the imbibition and germination stages of P. reticulataseeds, and they provide a better understanding of these important developmental events in plants.</description> </item> <item> <title/> <link></link> <description>ABSTRACTCattleya intermediais an Atlantic Forest species endemic to Brazil that is classed as vulnerable on the list of threatened species. In this study, C. intermedia plantlets were micropropagated in an asymbiotic culture and the influence of different concentrations of sucrose (15, 30, 45 and 60 g L-1, plus a zero sucrose medium) and macronutrient salts (complete Murashige and Skoog (MS) medium and half MS medium (with half-strength macronutrients)) on survival and development of the plantlets was evaluated. In all treatments 100% plantlet survival was achieved. The integrated analysis of height of aerial part, number of leaves per plantlet, fresh mass, number of roots per plantlet and length of the longest root showed that the plantlets exhibited greatest development at the half-strength macronutrient concentrations with 45 or 60 g L-1 of sucrose, as well as at the complete macronutrient concentration with 60 g L-1 of sucrose. Plantlets acclimatized and reintroduced to an environment in which the species occurs naturally exhibited 98.6% survival. The results obtained in this study allowed the establishment of optimal conditions for asymbiotic micropropagation, which is a requisite for future studies focused on conservation of C. intermedia.</description> </item> <item> <title/> <link></link> <description>ABSTRACTWe examined the distribution of Coccoloba cereifera,a tropical endemic species that occurs in a small area in the Espinhaço mountain range, southeastern Brazil. It is hypothesized that its narrow distribution is strongly related to the spatially scattered distribution of sandfields. However, this soil type extends far beyond the small region where C. cereifera is currently found, indicating that other factors might be involved in the distribution of this species. Coccoloba cereifera also displays all traits of a relict population in a microrefugium. As a result, we were encouraged to explore other factors potentially related to the distribution of the species. In an attempt to aid in the understanding of the processes and mechanisms that lead C. cereiferato present the narrow actual distribution, we applied two distribution modelling approaches to investigate the potential distribution of the species beyond the small known distribution area. The distribution seems to be strongly associated with sandy patches/grasslands formed among rocky outcrops and is limited by some topoclimatic and/or topographic features. Some of them related to the existence of a microrefugium, a fact also suggested by the pattern of distribution of the species in the past. From the management point of view, the existence of a microrefugium in this area calls for changes in conservation efforts and priorities.</description> </item> <item> <title/> <link></link> <description>ABSTRACTThe genus Sinningia belongs to the Neotropical tribe Gesnerieae, subtribe Ligeriinae, presently consisting of only three genera, Paliavana, Sinnigiaand Vanhouttea. These genera were separated from a larger concept of tribe Gloxinieae based on phylogenetic studies with molecular data. In Rio Grande do Sul, southern Brazil, 12 species and one natural hybrid of Sinningiahave been recorded. Species of Sinningia in this area are erect or ascending herbs or subshrubs arising from underground or partially exposed tubers. They grow in very distinct ecological conditions, from water-saturated marshes to dry grasslands or shrublands, but most often in rupicolous or epiphytic habitats commonly associated with forest environments. In this review we provide an identification key to the species level and morphological descriptions and illustrations, comments on taxonomic aspects, distributional maps and IUCN Red List Categories and Criteria for all twelve species. Additionally, we designate lectotypes for S. allagophylla and S. sellovii and consider the recently described S. lutea as a synonym of the highly variable S. allagophylla.</description> </item> <item> <title/> <link></link> <description>ABSTRACTWe investigated the existence of an ecotone in the species composition, diversity and vegetation structure in the transition between gallery forest and cerrado sensu strictoin central Brazil. We tested two hypotheses: 1) a ecotone can be found between gallery forest and cerrado; 2) a gradient exists in the species composition of the cerrado. We established three parallel transects of 5 m × 350 m running between gallery forest and cerrado, which were divided into subplots of 5 m × 10 m, perpendicular to the margin of the Bacaba stream in Nova Xavantina (Mato Grosso, Brazil). We identified and measured the height and diameter of individual plants in the plots with a diameter of at least 3 cm at 30 cm above the ground. We recorded 140 species, of which 26 were exclusive to the gallery forest, and 95 to the cerrado. The cerrado presented higher species richness (observed and estimated) and diversity (diversity profiles) than the gallery forest. Both hypotheses were accepted: a distinct ecotone was observed between gallery the forest and cerrado, and a pronounced gradient was found in species composition among the cerrado plots, apparently in response to the variation in soil moisture content, probably related to topography.</description> </item> <item> <title/> <link></link> <description>ABSTRACTMistletoes obtain nutrients and water from their hosts, with varying effects among those hosts. We assessed the factors that influence the colonization of the mistletoe Struthanthus flexicaulis on Baccharis dracunculifolia and the subsequent effects on host performance. We evaluated the incidence of S. flexicaulis according to size (height classes) and architecture of the host as well as its effects on various physiological parameters of the host. Furthermore, we assessed the occurrence of insect galls induced by Baccharopelma dracunculifoliae(Psyllidae), including the number of leaves infected, and the mortality of infected and non-infected branches. Taller hosts had a higher abundance of mistletoes (60%, p&gt; 0.05). Physiological parameters of hosts were not affected by parasitism, although galling occurred more often (p &lt;0.05) and leaf loss increased (p&gt;0.05) on infected branches. Taller individuals are more colonized by mistletoes and more architecturally complex hosts support a greater number of mistletoes. Mistletoe causes a top-down effect on host-associated organisms on parasitized branches. Mistletoes had a strong top-downeffect on B. dracunculifolia due to a reduction in the number of leaves on parasitized branches and the replacement of the bush crown, as well as an increased incidence of insect galls. Furthermore, the occurrence of a heavy parasite load increased the mortality rate of the host branches.</description> </item> <item> <title/> <link></link> <description>ABSTRACTA number of conifer species are still lacking anatomical data, which is significant because morphological and anatomical data are essential for systematic study. Leaf anatomy was studied in selected species of Abiesand Piceausing light and scanning electron microscopy. Both genera were found to have typical coniferous and highly xerophytic leaves with sunken stomata and an epidermis covered by a thick cuticle. In the genus Abies, species can be differentiated by the nature of the lignified hypodermis and the number and position of resin ducts. Abies firma and A. holophylla have a continuous hypodermis whereas in A. koreana and A. nephrolepis the hypodermis is discontinuous and represented by isolated cells or groups of four or five cells. On the other hand, in Picea leaf shape, stomata arrangement, and number, position, and nature of resin ducts are the key features for species differentiation. Picea jezoensis has a flattened leaf with stomata distributed on the adaxial surface whereas P. abies and P. koraiensis have a rectangular leaf with stomata found on surfaces.</description> </item> <item> <title/> <link></link> <description>ABSTRACTThe taxonomy, diversity and conservation status of all species of the family Pottiaceae in the Atlantic Rainforest of Rio de Janeiro State in southeastern Brazil are presented. The Atlantic Rainforest is a globally recognized biodiversity hotspot. The treatments are based on field expeditions and studies of herbarium collections. Twenty eight species from 18 genera are discussed. A key to the genera and species is provided, with comments on their distributions and altitudinal ranges, with illustrations and evaluation of the conservation status.</description> </item> <item> <title/> <link></link> <description>ABSTRACTIn seasonally dry tropical forests, species carrying attributes of Stress Resistance Syndrome (SRS) may have ecological advantages over species demanding high quantities of resources. In such forests, Poincianella bracteosa is abundant, while Libidibia ferrea has low abundance; therefore, we hypothesized that P. bracteosa has characteristics of low-resource species, while L. ferrea has characteristics of high-resource species. To test this hypothesis, we assessed morphological and physiological traits of seedlings of these species under different water regimes (100%, 70%, 40%, and 10% field capacity) over 85 days. For most of the studied variables we observed significant decreases with increasing water stress, and these reductions were greater in L. ferrea. As expected, L. ferreamaximized their growth with increased water supply, while P. bracteosa maintained slower growth and had minor adjustments in biomass allocation, characteristics representative of low-resource species that are less sensitive to stress. We observed that specific leaf area, biomass allocation to roots, and root/shoot ratio were higher in L. ferrea, while biomass allocation to leaves and photosynthesis were higher in P. bracteosa. Results suggest that the attributes of SRS can facilitate high abundance of P. bracteosa in dry forest.</description> </item> <item> <title/> <link></link> <description>ABSTRACTStudies on phenotypic variation among populations growing in different microenvironments may provide information about plasticity related to environmental pressures, and thus help to elucidate the potential evolutionary forces contributing to the origin and maintenance of diversity in any region. In this study we investigate morphometric variation on a small geographic scale for three species of Antarctic mosses. All species revealed significant differentiation among populations for all evaluated traits. The comparison of morphometric measures of populations of Polytrichum juniperinumfrom Nelson Island and from southern Brazil suggests that the effects of a small geographic scale in Antarctica are the same as a large geographic scale in environments where the climate is more homogeneous and microhabitats have minor influence on vegetation. However, further investigations over a larger area, evaluating more species, and using controlled garden experiments are recommended in order to evaluate the capacity for plasticity of moss species in different climatic conditions and on different geographic scales.</description> </item> <item> <title/> <link></link> <description>Pollen grains from twelve species of the Passifloraceae family from the Brazilian Atlantic Forest were analyzed: Passiflora subg. Astrophea (1sp.), P.subg. Decaloba (1sp.) and P.subg. Passiflora (10spp.). The current study aims to acquire additional information and feature the pollen morphology of the herein studied species to help setting a more precise taxa delimitation. Acetolyzed pollen grains were measured, described and illustrated using light and scanning electron microscopy. The pollen grains were medium or large sized, oblate spheroidal, suboblate, prolate spheroidal and subprolate; 4-colpate (P. kermesina), 6-12-pantocolporate (P. mediterranea), 6-colpate (P. mucronata), 6-colporate (P. pentagona), 12-colporate (P. misera) or 6-syncolpate (in most species). The presence of reticulate sexine, pseudopercula, pontopercula and/or opercula was observed. The endoaperture was just found in P. pentagonaand P. misera. It was concluded that pollen morphology is an important source of taxonomic features useful for distinguishing species and characterizing the three subgenera. The current study provides additional information that, along with other previously published studies, will enable a better understanding of phylogenetic relations among these strains.</description> </item> <item> <title/> <link></link> <description>ABSTRACTTo better understand the role that flooding plays in shaping plant communities of native floodable grasslands of the Pantanal and to characterize the spatial distribution of plants, we present the results of a survey of soil seed and spore banks using the seedling emergence method. We hypothesized that terrain subjected to the deepest and longest flooding should have higher propagule abundance and richness. The species composition and distribution of seeds and spores in the soil were assessed at five sites using three sampling positions at each according to inundation intensity. In each sample position 2cm-thick soil samples were collected in quadrats to a depth of 10cm. Litter was also collected as an independent layer. Sample monitoring in the greenhouse resulted in the emergence of 5489 seedlings, or 6353 propagules.m-2. Both the litter layer and the deepest soil layer had low abundances. A total of forty-four morphospecies (16 families) were recorded. Both seedling abundance and species richness were concentrated in the more floodable center sections. Isoetes pedersenii, Eleocharis minima, Sagittaria guayanensis, Rotala mexicana, Eleocharis plicarhachis, and Panicum laxum were the most abundant species. The species composition and spatial distribution of the propagule bank suggests that flooding plays a crucial role in seasonal vegetation dynamics in Pantanal wetlands, mediated by the ability of the soil to host seeds and spores during dry season.</description> </item> <item> <title/> <link></link> <description>ABSTRACTFire can change the species composition, diversity, and structure of savanna vegetation, thus altering growth and mortality rates. Such changes in the woody vegetation of burned savanna forest were evaluated over four years in comparison to unburned savanna forest. All woody plants with a diameter at breast height &gt; 10 cm were measured in 100 permanent plots. Six months later, 38 of these plots were burned. Three and a half years later, all surviving individuals were re-sampled. Species richness, diversity, and the number of individuals did not change in the burned plots, although they had significantly higher (p &lt; 0.05) increases in basal area and mortality rates (5.1% year-1) than the unburned plots (3.0% year-1).Tachigali vulgarishad the greatest post-fire increase in basal area (53%). The results indicate that fire alters the dynamics and structure of the savanna forest, excluding the less fire-tolerant species and smaller individuals (? 15cm). Tachigali vulgaris is a key species for the recovery of savanna forest biomass due to its considerable post-fire gains in basal area, at least over the short term due to its short life cycle. It follows that frequent burning of savanna forest would result in a marked change in the species composition and structure of its woody vegetation.</description> </item> <item> <title/> <link></link> <description>ABSTRACTSyagrus glaucescens is an endemic palm found in the rupestrian grasslands of the Espinhaço Mountains in southeastern Brazil. It is highly associated with quartzitic soils and exhibits strong intra-specific morphological variation in the different areas where it occurs. Allometric traits were used to verify whether there are any significant differences in the morphological traits between populations of this species located in two distinct areas. In the region of the Serra do Cipó individuals exhibit decumbent stems whereas on the Diamantina Plateau stems are straight and perpendicular to the ground. Soil quality was related to plant morphological traits to test the hypothesis that allometric variation is influenced by soil nutritional differences. Stem shape and size differed significantly among individuals inhabiting the two different regions: individuals in Serra do Cipó were shorter and had fewer leaves compared to individuals found in the Diamantina Plateau. Water retention capacity and nutrient absorption of the soils of the two sites were markedly different. In Serra do Cipó the soils were more acid, with higher aluminum saturation and lower sand content compared to the soils in Diamantina. These traits correlated with stem shape and indicate that soil acidity and aluminum saturation influence the architecture of S. glaucescens.</description> </item> <item> <title/> <link></link> <description>ABSTRACTPollen morphology of 24 of the 33 species of three Bomareasubgenera, Baccata, Sphaerine, andWichuraea, was examined by light microscopy (LM) and scanning electron microscopy (SEM), or SEM alone. The studied species ofBomarea were stenopalynous, characterized by large, monosulcate monads with reticulate exine sculpture in most species. Opercula-like structures were present on the sulcus in B.huanucoand B.involucrosa. Differences in pollen size, exine thickness, and exine sculpture were observed. The studied taxa were divided into four major groups based on exine ornamentation observed under SEM: microreticulate, reticulate, coarsely rugulate, or finely rugulate-perforate. Pollen characters alone did not appear to correlate clearly with the current subgeneric classification of Bomarea, but they may have some taxonomic utility below the subgeneric level. The most reliable infrageneric classification of Bomarea can be achieved through combined analyses of morphological, palynological, and molecular data from larger samples of specimens of all the species.</description> </item> <item> <title/> <link></link> <description>ABSTRACTPsychotria is the largest Rubiaceae genus and one of the most abundant in the Atlantic Rainforest of Rio de Janeiro State. The present work aims to characterize and compare the wood of nine of these species. ThePsychotria wood were characterized by: slightly distinct growth rings; diffuse porosity; solitary vessels or on radial multiples of 2-6 or clusters of 3-5 vessel elements, with terminal and lateral simple perforation plates and vestured and alternate intervessel and vessel-ray pits; septate fiber-tracheids; and rare axial parenchyma. Although, the wood anatomy of thePsychotria may be considered homogeneous, the statistical analyses, based on qualitative and quantitative features, allowed the segregation of the species and indicated the importance of habit (arboreous or shrubby) on the wood anatomy of the species. It is worth mentioning that the sampling was realized in only one studied site (Ilha Grande), which contributed to the conclusion that the wood characteristics are more related to the specificities of each studied taxon than to with environmental variations.</description> </item> <item> <title/> <link></link> <description>ABSTRACTWe studied the effects of seed storage on germination and dormancy alleviation in three species of Fabaceae endemic to campo rupestrein southeastern Brazil. Fresh seeds of Collaea cipoensis, Mimosa maguirei and Mimosa foliolosawere set to germinate and germination of seeds after four, five and 13 years of storage was tested. Seed viability was maintained for all species after the full storage period. Seed storage significantly increased germination percentage and decreased germination time for C. cipoensisand M. foliolosa, suggesting the alleviation of physical dormancy with storage. However, we did not find evidence of dormancy alleviation in M. maguirei since stored seeds showed a decrease in germination in comparison to that of fresh seeds. Our data indicate species-specific storage-mediated dormancy alleviation, which will have important implications for restoration of campo rupestre.</description> </item> <item> <title/> <link></link> <description>ABSTRACTAlthough many studies have shown that the dispersion, increased abundance and dominance of cyanobacteria can be attributed to nutrient enrichment, we discuss features contributing to the dominance of Cylindrospermopsis raciborskii in a shallow, polymictic, subtropical coastal lake with low phosphorus and light limitation (Peri Lake). The presence and dominance of C. raciborskii in an environment with such characteristics emphasizes the idea that nutrients alone do not explain the high density of this cyanobacterium. Other features should be considered in explaining this species dominance, such as phosphorus storage and physiological flexibilitywhich seem to be key features to high densities in low phosphorus systems.</description> </item> <item> <title/> <link></link> <description>ABSTRACTHistorically, developed countries have benefited from the biodiversity and traditional knowledge of developing countries. Since the Convention on Biological Diversity (CBD) was approved, the world-view regarding access to biological resources has changed. This change marked the introduction of legal agreements regarding access to genetic resources, traditional knowledge and benefit sharing, seeking a fair return for owners and local communities. Unfortunately, as with most national laws, these legal devices complicated collection programs and research initiatives, and diminished the emphasis on the discovery of natural products. There remains a lack of discussion on the establishment of a fair international market value for the access to genetic resources. While Brazil still has advantages and opportunities in this arena, the issue sets barriers for research and development. The protective measures are being reviewed in the project bill 7735/2014, which brings improvements, yet it is still controversial. For this short communication we consulted journals, conference proceedings, as well as scientific and journalistic magazines to report some of the disastrous consequences of the implementation of national laws regarding CBD. We suggest a new focus for decision-making policies based on more efficient field inspections, the empowerment of traditional communities and further associated research in order to ensure the claims of CBD as well as to ratify the Nagoya Protocol.</description> </item> </channel> </rss> <!--transformed by PHP 05:11:40 26-11-2015-->