Resumo em Inglês:

There have been few taxonomic studies of centric diatoms in lotic freshwater environments in Brazil, especially in terms of those including nanoplanktonic forms, which are often neglected in studies of local floras, because of their small size or confusing taxonomy. This is the first study focusing on centric diatoms in the flora of the state of Bahia, in northeastern Brazil. Plankton and periphyton attached to Eichornia crassipes were collected in the winter of 2009 in the Cachoeira River. The diatoms were analyzed and described under light and electron microscopies. Seventeen infrageneric taxa were identified. Cyclotella was represented by five taxa, and concerning of similarities between diacritical features of species in this genus, their descriptions were thoroughly detailed. This was the first time that Cyclotella atomus var. marina, previously recorded only in coastal areas of Japan and Korea, has been documented in a river in South America. We also identified two diatom taxa previously unrecorded in the flora of Brazil: C. cryptica and C. meduanae. Finally, we present a detailed light, transmission and scanning electron microscopy analysis of Skeletonema potamos, a diatom rarely found in the Brazilian literature.

Resumo em Inglês:

We conducted a floristic survey of lycophytes and monilophytes in Rio Preto State Park, located in the municipality of São Gonçalo do Rio Preto, and in the surrounding areas, including the municipality of Felício dos Santos, in the state of Minas Gerais, Brazil. The study area is within the Espinhaço Mountain Range. Collections were made from June 1999 to August 2008, and the specimens were deposited in the Herbarium of the Federal University of Minas Gerais. Were identified 188 taxa (185 species, one subspecies and two varieties), distributed among 20 families and 60 genera. The most representative families were Polypodiaceae, with 35 species; Pteridaceae, with 24 species; Dryopteridaceae, with 23 species; Hymenophyllaceae, with 17 species; and Lycopodiaceae, with 13 species and one variety. The most species-rich genera were Elaphoglossum (n = 19), Asplenium (n = 12), Blechnum (n = 10) and Thelypteris (n = 9). Of the taxa recorded, nine are endangered species. Here we present a taxa checklist for the studied area, data regarding growth habit and vegetation type for each species, as well as comparative analyses between Rio Preto State Park and other areas within the Espinhaço Range and the Atlantic Forest, in terms of species composition.

Resumo em Inglês:

Seed dormancy is a widely misunderstood plant trait. In several research areas, a lack of germination is wrongly assumed to result from seed dormancy. In an attempt to standardize seed dormancy research and improve communication among seed scientists, a straightforward protocol to address the occurrence and causes of seed dormancy is provided. Standardizing communication is not just a theoretical exercise but also has practical implications in agriculture and conservation. Standardization will make studies comparable and hence we will have a deeper understanding of the physiology, ecology and evolution of seed dormancy. A better understanding of the various aspects of seed dormancy will lead to greater appreciation of the biogeographical and phylogenetic distribution of seed dormancy among our flora.

Resumo em Inglês:

Ecological theory predicts that, in mature ecosystems, species richness, the number of individuals and the biomass of individuals will remain in a relatively stable state of equilibrium. The aim of this study was to test that theory. In 2001 and 2010, we conducted censuses of all trees with a circumference at breast height > 10 cm in a one-hectare plot in a seasonal semideciduous old-growth forest in southeastern Brazil. We compared the two censuses in terms of species richness and diversity, computing growth, recruitment and mortality rates, as well as gains and losses of basal area. Between 2001 and 2010, species richness declined from 224 to 218 species and the basal area increased from 37.86 to 40.16 m² ha-1. Overall turnover (the mean difference between mortality and recruitment) was lower than would be expected for a seasonal semideciduous forest, indicating stability and slight successional advance. This interpretation is supported by the observation that pioneer species and canopy species both showed higher mortality than recruitment. However, uncommon species (< 10 individuals in the 2001 census) showed higher mortality than recruitment and became rarer, whereas most species that were abundant in 2001 became more abundant by 2010. These observations, as well as the decline in species richness, although statistically not significant, match the predictions of ecological theory for scenarios in which formerly contiguous ecosystems become fragmented and the remnants become isolated within the landscape. Nevertheless, further censuses are needed in order to test the idea that the observed patterns are not explained by natural oscillations but are consequences of environmental changes related to human activity.

Resumo em Inglês:

Ecosystems on cangas (duricrust) present considerable heterogeneity of habitats due to microtopographic variations, soil accumulation and a variety of plant functional groups. Therefore, spatial and temporal ecosystem processes such as litterfall are to be expected to be large, and the absence of a level of productivity represents all the facets of iron-rich landscapes. We investigated litterfall in a iron-rich rock complex in the Iron Quadrangle of Brazil, with habitats formed on different evolutionary stages of the soil, resulting in a gradient of biomass, canopy cover and community structure. The measurements were made in open field areas, dominated by herb-shrub vegetation and interspersed with islands of dense vegetation in which there were individual trees, as well as in areas of semideciduous forest. The litterfall, especially that of leaf litter, followed the gradient of woody cover and was approximately two times greater in the forest formation. However, the spatial and temporal variations in deposition were greatest in the herb-shrub areas and least in the semideciduous forest area, intermediate values being obtained for the tree island areas. The peaks in litterfall also varied among habitats, occurring in some periods of the rainy season and during the transition from rainy to dry in the herb-shrub and tree island areas, whereas they occurred at the end of the dry season in the semideciduous forest area. The results show significant differences in the patterns of litterfall among different physiognomies within the same iron-rich rock complex, indicating the need for expanded studies, focusing on the flow of matter and energy in such environments.

Resumo em Inglês:

The Chapada Diamantina ecoregion is within the caatinga (shrublands) biome of Brazil. Environmental factors determine the phytophysiognomies that distinguish the ecoregion from the surrounding areas. This study aimed to investigate the distribution of bryophyte flora in this ecoregion, by phytophysiognomy and elevational zone. Analyzing specimens we collected from five municipalities in the region, together with specimens (previously collected from the region) in herbaria, we identified 400 taxa. The phytophysiognomies that presented the highest species richness and the greatest numbers of exclusive taxa were forests and campos rupestres (dry, rocky grasslands), which respectively accounted for 51% and 40% of the taxa, compared with only 5% and 4%, respectively, for the caatinga and cerrado (savanna). Species richness and the numbers of exclusive taxa were highest in the lower and upper montane zones. There was a predominance of neotropical taxa and a significant number of disjunct species found in Brazil and in the Andes region. We conclude that the Chapada Diamantina region is an important center of bryophyte diversity, harboring not only a great number of species overall but also a considerable number of species exclusive to the region, primarily in forests and campos rupestres at elevations above 800 m.

Resumo em Inglês:

This work aimed to evaluate the effect that different intensities of light have on the physiological attributes of red rice seeds and seedlings. Before and after emergence, seedlings were exposed to light levels of 35%; 65% and 100% in a greenhouse. We evaluated shoots and roots, in terms of length and dry mass, as well as leaf area and content of chlorophyll (a,b and total). In leaves and roots, we quantified the activity of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and guaiacol peroxidase (POX). We determined the leaf area ratio (F A), leaf mass ratio (F W), specific leaf area (S A), and shoot/root ratio (P W). At higher light intensities, shoot length decreased, whereas root length, dry mass and number of tillers increased. Leaf area was greatest in seedlings exposed to a 65% light level. The F A, F W, S A and P W were lowest at a light intensity of 100%. Differences in light intensity had qualitative and quantitative effects on chlorophyll contents. The activity of SOD and CAT was higher at lower light levels, whereas the inverse was true for APX and POX activity. Extremes of light availability alter the activity of antioxidant enzymes, negatively affecting the initial growth characteristics and photosynthetic pigments of red rice seedlings.

Resumo em Inglês:

Salinity and fertility are the main factors cited in Within the restinga (coastal woodland) biome in Brazil, the positioning of Canavalia rosea and Passiflora mucronata occur, respectively, near the shore-in the creeping psammophyte formation (CPF) - and far from the shore - in the Palmae formation (PF). The hypothesis that such positioning is related to salinity and fertility was tested by applying a salt gradient (increasing solutions of NaCl) and a nutritional gradient (different proportions of Hoagland solution). Neither species survived in solutions over 200 mM of NaCl. The shoots of P. mucronata showed negative growth (lower dry mass) in the first week of exposure to saline solutions. The roots of C. rosea showed great sensitivity to salinity, which resulted in greater growth reduction, with increasing plant age, in comparison with P. mucronata. C. rosea grew best in the nutrient-deficient solution, whereas P. mucronata responded best to the nutrient-rich solution, suggesting that C. rosea is better able to populate less fertile sites, such as the CPF, whereas P. mucronata is more suited to sites that are more fertile, such as the PF. Therefore, we can speculate that fertility is the only factor limiting the positioning of species in the restinga.

Resumo em Inglês:

This study presents results of the inventory of algal flora conducted between August 2007 and May 2008 in 18 lakes of the middle Rio Doce lake system, most of which is in the state of Minas Gerais, Brazil. We recorded 481 taxa, increasing the known total phytoplankton diversity of the region (gamma diversity) by 80%. The following classes were represented: Zygnematophyceae (171 taxa), Cyanobacteria (101), Chlorophyceae (71), Bacillariophyceae (42), Euglenophyceae (43), Trebouxiophyceae (24), Dinophyceae (8), Xanthophyceae (8), Chrysophyceae (6), Cryptophyceae (6) and Oedogoniophyceae (1). We identified 221 taxa that were rare (restricted to one or two lakes), and 101 that were considered representative (present in at least nine lakes). Botryococcus braunii, Elakatothrix genevensis, Planktolyngbya limnetica, Peridinium pusillum, Trachelomonas volvocina, Cosmarium contractum, Staurastrum forficulatum, Staurastrum leptocladum, Staurastrum rotula, and Staurodesmus dejectus were present in all lakes. Richness varied from 95 taxa (in Lake Gambazinho) to 168 taxa (in Lake Palmeirinha). Jaccard indices were low, and the highest similarities between lakes were 53% (Ferrugem/Ferruginha), 47% (Central/Almécega) and 46% (Águas Claras/Palmeirinha), demonstrating high environmental and biotic dissimilarities between lakes. Geographic distance was not significantly associated with floristic similarity, suggesting that local factors are more important than are regional ones in shaping the phytoplankton composition of lakes.

Resumo em Inglês:

Epiphytic bryophyte communities in terra firme forests of the Amazon region were investigated for the first time through standardized sampling across the Amazon basin. The sampling was carried out at nine localities, where bryophytes were collected in five height zones, from the forest floor to the canopy of eight canopy trees per locality. The sampling generated 3104 records, identifying 222 species and 39 morphospecies, within 29 families. The most common families were Lejeuneaceae (in 55%), Calymperaceae (in 8%), Leucobryaceae (in 4%) and Sematophyllaceae (in 4%). Richness and species composition did not show any geographical gradient. The bryoflora was significantly richer in the localities of Saül, in French Guiana, and Tiputini, in Ecuador, than in the other localities, probably due to differences in local climatic conditions. Among the 155 species recorded for more than one locality, 57 were classified as specialists. A total of 29 species (among which 3 were unidentified) were sampled only in the canopy, which reinforces the importance of canopy sampling for the study of epiphytic bryophytes in the Amazon.

Resumo em Inglês:

During the various hydrological periods in 2011, we studied the phytoplankton along an 87-km stretch of the Araguari and Falsino rivers, which are located in the eastern Brazilian Amazon, in the state of Amapá, Brazil, the most ecologically preserved state in the country. In the study area, the aquatic ecosystem is under pressure from human activities such as, mining, hydroelectric power generation and urbanization, which contrast with the surrounding areas that are designated for biodiversity conservation. The aim of this study was to characterize the composition, frequency and richness of algae species and also to identify spatial-temporal patterns of taxa distribution. During the study period, we identified 185 taxa (136 species in 49 genera). The division Chlorophyta (class: Zygnematophyceae) presented the greatest number of taxa, whereas the division Rhodophyta accounted for only 1% of the taxa recorded. Most of the species identified (69%) were classified as sporadic in occurrence. The few taxa that were classified as common belonged mainly to the group Bacillariophyta. Species richness was greatest richness in the lentic stretches (in a reservoir) and in November (during the dry season). Of the 185 taxa identified, 174 are new records for the state of Amapá.

Resumo em Inglês:

This survey aimed to describe the floristic composition and structure of the epiphytic community occurring in a terra firme forest in the city of Coari, Brazil, in the Amazon region. Data collection was performed with a 1.5 ha plot method, with which upland, slope and lowland habitats were sampled. All angiosperm epiphytes and their host plants (diameter at breast height > 10 cm) were sampled. We recorded 3.528 individuals in 13 families, 48 genera and 164 species. Araceae was the most prevalent family with regard to the importance value and stood out in all related parameters, followed by Bromeliaceae, Cyclanthaceae and Orchidaceae. The species with the highest epiphytic importance values were Guzmania lingulata (L.) Mez. and Philodendron linnaei Kunth. The predominant life form was hemiepiphytic. Estimated floristic diversity was 3.2 (H'). The studied epiphytic community was distributed among 727 host plants belonging to 40 families, 123 genera and 324 species. One individual of Guarea convergens T.D. Penn. was the host with the highest richness and abundance of epiphytes. Stems/trunks of host plants were the most colonized segments, and the most favorable habitat for epiphytism was the lowlands, where 84.1% of species and 48.2% of epiphytic specimens were observed.

Resumo em Inglês:

The germination and development of several plant species can be limited when those plants are grown in soils with high salinity, which reduces seedling viability and vigor, as well as activating the antioxidant defense system. The aim of this study was to evaluate germination, initial growth and activity of antioxidant enzymes (superoxide dismutase, catalase and ascorbate peroxidase) in seedlings of three onion cultivars (Madrugada, Fepagro 27 and Petroline) exposed to different concentrations of NaCl (0, 40, 80, 120 and 160 mM). Seedlings were evaluated for viability, vigor and antioxidant enzyme activity. The experimental procedures were completely randomized in 3 × 5 factorial design, with each treatment performed in triplicate, at a significance level of 5%. For all cultivars, viability and vigor decreased in parallel with increasing NaCl concentrations, whereas antioxidant enzyme activity increased, and one cultivar (Madrugada) showed less salt tolerance than did the others. We conclude that high NaCl concentrations have a negative effect in the physiological quality of onion seeds, resulting in lower seedling growth rates and increased antioxidant enzyme activity, where Fepagro 27 and Petroline cultivars were more tolerant to salt stress than 'Madrugada'.

Resumo em Inglês:

We analyzed the pollen grains of 30 taxa of the genus Bauhinia L., within five series: Aculeatae (9 species); Acuminatae (1 species); Cansenia (17 species); Pentandrae (2 species); and Perlebia (1 species). The pollen grains were acetolysed, after which they were photographed and analyzed under light microscopy. Non-acetolysed pollen grains were analyzed under scanning electronic microscopy. Characters such as shape, size, exine and aperture constitution were studied. The species were separated by a dichotomous key, which showed pollen grains that were classified as very large; isopolar or apolar; oblate, suboblate, oblate spheroidal or spherical; large or small in terms of the polar area; inaperturate, 3-porate or (3-7)-colpate; and microreticulate or reticulate, with or without supratectal elements (gemmae, bacula, clavae). The variation in pollen morphology confirms the eurypalynous status of the genus Bauhinia.

Resumo em Inglês:

Pseudolaelia is a genus endemic to eastern Brazil. The species are often epiphytes on Velloziaceae or are saxicolous, predominantly on granitic and gneissic outcrops (inselbergs) in the Atlantic Forest and, less often, in the campos rupestres (dry, rocky grasslands) of the cerrado (savanna) and caatinga (shrublands). The genus is characterized by homoblastic pseudobulbs, long rhizomes, long and usually slender inflorescences, racemes or panicles, bearing pink, yellow or whitish flowers, labellum often 3-lobed, with simple, fimbriate or erose margin, semi-cylindrical or claviform column, cuniculus present. Twelve species are recognized; seven binomials are placed in synonymy. Of those seven, three are considered illegitimate because, contrary to the International Code of Botanical Nomenclature guidelines, there are no corresponding type specimens deposited in a recognized herbarium, and those three were therefore lectotypified. We present descriptions of, illustrations of and a dichotomous key to Pseudolaelia species, as well as addressing their taxonomy, ecology, conservation and geographic distribution.

Resumo em Inglês:

There have been few palynological studies of the family Menispermaceae. Here, we analyzed the pollen grains of 12 species from seven genera of Menispermaceae occurring in the state of Bahia, Brazil: Abuta selloana Eichl.; Borismene japurensis (Mart.) Eichl.; Chondrodendron microphyllum (Eichl.) Moldenke; C. platyphyllum (A.St.-Hil.) Miers; Cissampelos andromorpha DC.; C. ovalifolia DC.; C. pareira L.; C. sympodialis Eichl.; Hyperbaena domingensis (DC.) Benth.; Odontocarya duckei Barneby; Sciadotenia campestris Barneby; and S. pubistaminea (K. Schum.) Diels. The pollen grains were acetolysed, measured, described, and illustrated using light and scanning electron microscopy. The pollen grains were found to be small, oblate spheroidal or prolate spheroidal, isopolar, and tricolpate or tricolporate; the exine was found to be reticulate. It was concluded that the various genera can be separated based on pollen characters. Within each of the genera, the species studied were stenopalynous. For five Menispermaceae species, pollen descriptions are presented here for the first time.

Resumo em Inglês:

This study describes the influence of edaphic factors on the floristic composition of an area of cerradão (woodland savanna) in the city of Campo Grande, located in the Brazilian central-west. In 10 plots (5 × 20 m each), we evaluated all trees with a diameter at breast height > 4.77 cm. Soil samples were analyzed for each plot in order to determine edaphic variables correlated with species composition. We sampled 1180 individuals of 61 species. The evenness index was 0.74, which indicates uneven distribution of species, which was explained by a high abundance of Qualea parviflora, Curatella americana, Qualea grandiflora, Terminalia argentea and Astronium fraxinifolium. We registered more trees in the smallest diameter class and in the middle layer of the vertical structure. The soil was dystrophic with a clay texture, which explains the higher abundance of species related to dystrophic cerradão. However, we also found some trees typical of mesotrophic cerradão and deciduous forests, which could be attributable to the presence of patches of fertile soil within the dystrophic cerradão or could indicate that those mesotrophic species are tolerant of lower levels of soil nutrients.

Resumo em Inglês:

In this study, we evaluated the phenological patterns (vegetative and reproductive) of Calotropis procera (Apocynaceae-Asclepiadoideae) in Brazil, comparing its phenology in an area where it is invasive with that observed in areas to which it is native. Phenological observations were carried out over a 24-month period at sites in and around areas of caatinga (shrublands). We estimated the relative frequency of each phenophase, and we documented a dramatic difference between phenophases in terms of the pattern of reproductive phenology . The pattern of continuous flowering and fruiting observed in the invaded area strongly diverges from the 2- to 6-month flowering and fruiting period of the annual pattern. The continuous pattern of reproduction seems to have facilitated the invasion of the Brazilian caatinga by C. procera.

Resumo em Inglês:

In this study, we identified six polyporoid species of Agaricomycetes: Abundisporus roseoalbus, Fuscocerrena portoricensis, Oligoporus caesius, Antrodiella duracina, Inocutis jamaicensis and Inonotus venezuelicus. All of these represent new records for the state of Santa Catarina, located in southern Brazil. For Brazil as a whole, this is the second record of O. caesius.