Scielo RSS <![CDATA[Acta Botanica Brasilica]]> vol. 30 num. 1 lang. <![CDATA[SciELO Logo]]> <![CDATA[Algicidal effects of aqueous leaf extracts of neem (Azadirachta indica) on Scenedesmus quadricauda (Turp.) de Brébission]]> The application of synthetic algaecides for the control of algae produces by-products that are sometimes toxic to the environment. There is a need for natural and cheap alternatives to synthetic algaecides. In the present study, we investigated the potential of aqueous crude extract of Azadirachta indica to inhibit the growth of Scenedesmus quadricauda. Phytochemical screening of the extract revealed the presence of groups of bioactive compounds that are capable of inhibiting microalgal growth. Chlorophyll a concentration, dry weight production and cell density of microalga decreased with increasing crude extract concentration. After three days of exposure, the 1000 mg/L extract concentration resulted in complete growth inhibition and cell lysis. Furthermore, the ability of S. quadricauda to form multi-celled coenobial structures was compromised in a concentration dependent manner. In general, catalase and peroxidase activities of the microalga were upregulated with increasing extract concentration. These results imply that aqueous neem extract may provide a cheap and ecofriendly alternative for the control of microalgae in aquatic ecosystems. <![CDATA[Influence of arbuscular mycorrhizal fungi inoculum produced on-farm and phosphorus on growth and nutrition of native woody plant species from Brazil]]> Mycorrhizal fungus inoculum produced on-farm can be used during production of woody plant seedlings to reduce costs associated with purchase of commercial inoculant and fertilization. This study aimed to test the efficiency of a mycorrhizal inoculant produced on-farm to promote growth and nutrition of woody species in combination with different levels of phosphorus. Plants were submitted to different treatments of phosphorus (0, 40 and 80 mg P/dm3) and mycorrhizal inoculation (uninoculated, and inoculation with Rhizophagus clarus [Rc] or Claroideoglomus etunicatum [Ce]). Species included were Luehea divaricata, Centrolobium robustum, Schinus terebinthifolius, Garcinia gardneriana, Cedrella fissilis, and Lafoensia pacari. The inoculum was produced using the on-farm methodology. Mycorrhizal colonization of plants inoculated with Rc and Ce ranged from 44.8 to 74.8%, except forGarcinia gardneriana. Inoculation treatment increased plant height and stem diameter of Luehea divaricata, Centrolobium robustum and Cedrella fissilis while phosphorus, inoculation and the interaction affected these parameters for G. gardneriana and Lafoensia pacari. Shoot biomass increased significantly with inoculation treatment in four species. For most species, mycorrhizal fungus inoculation and the addition of phosphorus increased the shoot phosphorus content. Mycorrhizal fungus inoculum produced on-farm successfully colonized tree seedlings and improved growth and/or nutrition under nursery conditions, producing seedlings useful for revegetation of degraded lands. <![CDATA[Ecophysiological performance of a threatened shrub under restored and natural conditions in a harsh tropical mountaintop environment]]> Ecophysiological responses of plants are useful for monitoring the success of ecological restoration projects that target species conservation. In this study we evaluated the ecophysiological traits of individuals of Chamaecrista semaphora from a natural population and from a site under restoration. Water potential and chlorophyll a fluorescence parameters were measured both in adult and young plants of the two populations. No difference in water potential was found between sites, but individuals in the restored site had higher water potential at predawn. Adults in the natural site presented lower daily values of potential quantum yield, indicating the occurrence of photoinhibition. Individuals in the restored site also presented higher maximum relative electron transport rate (ETRMAX). No difference was found in leaf carbon isotope discrimination values (σ13C) between plants growing in restored and natural sites, suggesting similar water use efficiency. These results indicate that C. semaphora individuals in the restored site had similar or better photosynthetic and water economy performances than individuals at the natural site. Methodologies traditionally employed to assess stress response of plants, such as chlorophyll a fluorescence and procedures used to evaluate the efficiency of water use, allowed us to verify the success of restoration procedures using an endangered species. <![CDATA[Variation in plant-animal interactions along an elevational gradient of moist forest in a semiarid area of Brazil]]> Pollination and dispersal are critical ecological processes that directly affect the reproductive success of plants and are important for understanding the structure of plant communities. We compiled data on pollination and dispersal syndromes of 406 plant species distributed among different elevations in Área de Proteção Ambiental da Serra de Baturité (APASB) in northeastern Brazil. We aim to determine how the dispersal and pollination of the flora in the mountainous rainforest of APASB are affected by climate, relief and growth form. We hypothesized that plant community is comprised of different ecological groups based on biotic and abiotic syndromes. Melittophily was the most common (57%) pollination syndrome followed by non-specialized and ornithophily (7%). We found that 64% of species exhibited zoochory, 19% exhibited anemochory and 17% exhibited autochory. Pollination syndromes differed significantly only between types of growth form. Dispersal syndromes differed between topology, growth form and elevation. Six ecological groups were formed based on the interaction between dispersal-pollination and growth form, with predominantly zoochory in woody and anemochory in non-woody plants. Water availability may be the principal factor responsible for variation among dispersal syndromes. The proportion of ruderal species in the non-woody component explains the differences in syndromes between growth forms. <![CDATA[Maternal habitat affects germination requirements of Anabasis setifera, a succulent shrub of the Arabian deserts]]> The effects of maternal habitat on light and temperature requirements during germination were assessed for the succulent desert shrub Anabasis setifera. Seeds were collected from the Mediterranean habitats of Egypt and the hyper-arid subtropical habitats of the United Arab Emirates (UAE). Seeds from the two populations were germinated in three temperature treatments in both a light/dark regime and continuous darkness. Seeds from the Egyptian population germinated significantly greater and faster than those of UAE. Seeds stored for four months at room temperatures have little dormancy and germinate at wide range of temperatures and light conditions, but seeds stored four months in the natural habitat lost their ability to germinate and rotted 10 days after incubation. The germination response to temperature depended on the habitat type. Seeds of the Egyptian population attained a significantly greater germination at lower temperatures, compared with seeds from the UAE population, but there was no difference in germination between the two populations at higher temperatures. Germination of A. setifera was very fast; most seeds germinated within four days. These results reflect the adaptive strategy of germination in both populations, and may help explain the wide distribution of this species in different climatic regions. <![CDATA[Host preference of the hemiparasite Struthanthus flexicaulis (Loranthaceae) in ironstone outcrop plant communities, southeast Brazil]]> Struthanthus flexicaulis is a hemiparasite abundant in ironstone outcrops in southeast Brazil. We evaluated its host preference among species of the plant community, taking into account the abundance and foliage cover of the hosts. The importance of each species in the community and the mortality caused by the parasite were assessed based on a quantitative survey in 10 strips measuring 1m x 50m. The 10,290 individuals belonged to 42 species. Only 15 had a relative abundance in the plant community greater than 1%, of which 12 showed vestiges of parasitism. More than 80% of deaths in the community were associated with parasitism. Non-infected individuals had significantly less mortality rates (7%) than those infected (83%) (²= 1102.4, df = 1, p &lt; 0.001). The observed infestation was different from the expected both regarding relative host abundance (²= 714.2, df = 11, p&lt;0.001) and foliage cover (²= 209.2, df = 11, p&lt;0.001). Struthanthus flexicaulis preferredMimosa calodendron, a legume attractive to avian seed dispersers. The interaction is maintained and intensified not only by the birds, who deposit innumerous seeds on the hosts branches, but also very likely by the ability of M. calodendron to fix nitrogen, thereby enhancing the mistletoe's development. <![CDATA[Ethnobotany and antioxidant evaluation of commercialized medicinal plants from the Brazilian Pampa]]> Despite the importance of medicinal plants for the healthcare of local people, the knowledge about medicinal species used in the Pampa biome has been neglected over the years. In this study, an ethnobotanical survey was employed aiming to characterize the species richness and diversity of commercialized medicinal plant species in five cities within the Brazilian Pampa. Additionally, among the listed plants, ten species were selected for in vitro testing of their potential antioxidant activity. A total of 56 plant species belonging to 33 botanical families were listed by the 115 interviewees. No significant difference in commercialized medicinal plant species, and very similar species richness was observed among the cities, indicating that the local knowledge is consistently preserved across the studied cities. According to the biochemical analysis, Sphagneticola trilobata, Malva parviflora and Struthanthus flexicaulis emerged as very promising species for antioxidant activity. Further studies are recommended to advance our knowledge about the richness of medicinal plant species in the Brazilian Pampa, and to assess their therapeutic potential. <![CDATA[Selaginella P. Beauv. from Minas Gerais, Brazil]]> Selaginella P. Beauv. is the only genus in the family Selaginellaceae Willk. The genus is monophyletic, has a cosmopolitan distribution, contains about 750 species and can be characterized by the presence of rhizophores, leaves, a ligule, heterospory and adaxial, reniform sporangia. Twenty species were found in the study area: Selaginella alstonii, S. contigua, S. convoluta, S. decomposita, S. erectifolia, S. erythropus, S. flexuosa, S. jungermannioides, S. macrostachya, S. marginata, S. microphylla, S. muscosa, S. producta, S. sellowii, S. sematophylla, S. suavis, S. sulcata, S. tenella, S. tenuissima and S. vestiens. Two new species records for the state are presented (S. jungermannioides and S. tenella). We present descriptions of the genus and species, an identification key, the synonyms pertaining to Brazil, illustrations, and comments about the taxonomy and distribution of species in Brazil. <![CDATA[Tree species of South America central savanna: endemism, marginal areas and the relationship with other biomes]]> Biological knowledge is important for guidance of conservation polices. In the Cerrado, an extremely diverse biome, the last synthesis of floristic knowledge has more than ten years. To understand the progress on the information, our aim was quantify the tree species of the Cerrado, and assess their distribution. We compiled 167 inventories and rapid surveys of tree species, corresponding to 625 sites. We accessed the species distributions in the Brazilian biomes, and estimated the number of species in the savannas of Cerrado using four algorithms. We observed a greater local richness in more central regions of the biome, but due to high beta diversity, more peripheral regions presented a greater cumulative richness. The Atlantic Forest was the most important neighbouring biome, influencing the floristic composition of the Cerrado. The proportion of typical Cerrado species was 16%. The highest proportion of endemic species is possibly found in other life forms, and it is crucial that these species are included in inventories and floristic surveys. To guide new studies and help supplement the knowledge of the Cerrado's flora, we identified the main sampling gaps, located mainly in ecotonal regions, which are responsible for the largest number of species recorded in studies of the Cerrado. <![CDATA[Factors influencing seed germination in Cerrado grasses]]> Few studies address the ecology of herbs of Cerrado grasslands, which are ecosystems where the long dry season, high temperatures, insolation, fire and invasive grasses greatly influencing germination and the establishment of plants. We assessed germination of 13 species of Poaceae from Cerrado grasslands under nursery conditions or in germination chambers, the latter with i) recently collected seeds and seeds after six months storage, ii) under constant and alternating temperatures, and iii) in the presence and absence of light. Germinability, mean germination time (MGT) and required light were quantified to elucidate factors involved in successful germination. Germinability was low for most grasses, probably because of low seed viability. For most species, germinability and MGT were not altered by seed storage. Germination percentages were higher at alternating temperatures and in the presence of light, factors that are more similar to natural environmental situations compared with constant temperature or the absence of light. Our findings indicate that alternating temperatures and light incidence are key factors for germination of species of Poaceae. The maintenance of these environmental factors, which are crucial for the conservation of Cerrado grasslands, depends on appropriate management interventions, such as fire management and the control of biological invasion. <![CDATA[Could biological invasion by Cryptostegia madagascariensis alter the composition of the arbuscular mycorrhizal fungal community in semi-arid Brazil?]]> Biological invasions pose a serious threat to native semi-arid areas of Brazil, especially in areas of the state of Ceará that are typically invaded byCryptostegia madagascariensis, an exotic plant species from Madagascar. However, how this biological invasion influences the composition of the arbuscular mycorrhizal fungal (AMF) community and how this affects further invasion by C. madagascariensis is not well known. Here we tested how inoculation with species of AMF affects the development of this invasive plant. We analyzed and compared the AMF community composition of four different stages of biological invasion by C. madagascariensis, and examined the effects of inoculation with these four AMF communities, plus a dominant AMF species (Rhizoglomus intraradices) on plant dry biomass, root colonization, plant phosphorous concentration, and plant responsiveness to mycorrhizas of plants of C. madagascariensis. We found that all studied treatments (except the inoculum from the native plant root zone) promoted the growth of C. madagascariensis and lead to a higher P concentration. Our results demonstrate that the invader might be altering the composition of the AMF community in field conditions, because inoculation with this community enhanced invader growth, root colonization, and P uptake. <![CDATA[Occurrence and distribution of Perichaena (Trichiaceae, Myxomycetes) in the Brazilian Northeastern Region]]> The known distribution of Perichaena calongei, P. chrysosperma, P. corticalis, P. depressa, P. microspora, P. pedata and P. vermicularis in the nine states that comprise Brazil's Northeast Region (1,548,672 km2) is presented herein, enhancing our understanding of the distribution of the genusPerichaena (Trichiaceae, Myxomycetes) in the Neotropics. This inventory encompasses a 100-year period (1914-2014), and analyzes material deposited in herbaria and collected by the authors. The collected material came from areas of thorny deciduous vegetation typical of the Caatinga biome and portions of savannah in the continent's interior, rainforests,restingas (tropical moist broadleaf forests found along Brazil's coastal spits) and mangroves of the Atlantic Forest biome along a coastal zone of approximately 3,000 km. Descriptions, illustrations, vegetational environments, microhabitats and distribution maps are given for each species. New records include Perichaena chrysosperma andP. depressa in the state of Maranhão, P. corticalis in the states of Bahia, Piauí, Rio Grande do Norte and Sergipe, P. calongei in the Northeast Region, and P. pedata in Brazil. This paper adds to the known types of macroclimates, elevation levels, vegetational environments and substrates for these species and provides a better understanding of their global distribution pattern. <![CDATA[Comparative anatomy of calyx and foliar glands of Banisteriopsis C. B. Rob. (Malpighiaceae)]]> Banisteriopsis is considered one of the largest genera of Malpighiaceae with 58 species, of which 47 occur in Brazil. The typical calyx and leaf glands of Banisteriopsis are considered relevant to the adaptive success of Malpighiaceae. Comparative studies of anatomical and histochemical characteristics may reveal similarities and assist in the interpretation of the functions performed by such glands. The present study aimed to describe the anatomy of the calyx and leaf glands of 38 species ofBanisteriopsis that occur in Brazil, and to analyze these structures histochemically in B. campestris, B. laevifolia and B malifolia, using standard methods. Calyx glands differ from leaf glands by possessing an irregular surface that is covered by a thick cuticle that is released from the epidermis by the accumulation of secretion; the glands are similar in all the other anatomical characteristics. Both types of glands produce secretions composed of a mixture of protein granules, lipids and polysaccharides. These findings reinforce the hypothesis that foliar glands have given rise to calyx glands in response to interactions with pollinators. <![CDATA[Ecological significance of wood anatomy of Alseis pickelii Pilg. & Schmale (Rubiaceae) in a Tropical Dry Forest]]> This work describes, analyzes and compares the wood anatomy of Alseis pickelii from two distinct sites in Tropical Dry Forest. One site is an exploited forest that was disturbed by deforestation whereas the other site is preserved and has not been logged since selective logging in the 1960's. For the evaluation of wood anatomy, plant material was processed following standard techniques for light microscopy and histochemical tests. The results indicated that A. pickelii did not vary qualitatively between the two sites. The histochemical tests indicated the presence of prismatic crystals and starch in radial parenchyma of samples from both sites. Some quantitative parameters differed significantly between the two sites including: vessel frequency; vessel length and lumina area; intervessel pits; diameter, lumina, length and wall thickness of fibres; and radial parenchyma width. In general, these quantitative parameters had higher values in the samples from the exploited site, suggesting an adjustment to the more severe drought conditions there. Quantitative anatomical differences in the samples from the two sites show the influence that environmental conditions can have on wood anatomy. The observed anatomical characteristics may also be useful for taxonomic and ecological studies of this species and genus. <![CDATA[Disturbance as a factor in breaking dormancy and enhancing invasiveness of African grasses in a Neotropical Savanna]]> The Cerrado is threatened by wildfires and invasive species. We aimed to evaluate in laboratory conditions whether temperature fluctuation at the soil surface, resulting from the absence of vegetation due to fire, can affect the germination of Urochloa decumbens and U. brizantha, two invasive African grasses. Seeds of both species were submitted to simulations: 1) temperature during fire at 1cm belowground (F); 2) temperature fluctuation at 1cm belowground without vegetation cover for a month (TF); 3) (F) + (TF); 4) control at 25ºC. After treatments, seeds were put to germinate at 25ºC for 40 days. We had four replicates per treatment and three temporal replicates. We compared germination percentage and the mean germination time among treatments using ANOVA. The treatments TF and F+TF had the highest germination values for both species. The results showed that fire per se could not stimulate seed germination, however, they suggest that a disturbance that produces a pattern of temperature fluctuation is able to break dormancy and enhance seed germination and, consequently, increase the invasiveness of the study species. Vegetation gaps resulting from disturbance may become new sites of invasion. This information is important for making management decisions regarding the control of these species. <![CDATA[Pollen morphology of species of Graphistylis B. Nord. (Asteraceae) of Brazil]]> This paper presents the results of a palynological study of the species ofGraphistylis that were segregated fromSenecio (s.l.) (Seneciosect. Dichroa) and that are all endemic of Brazil. These species are found in mountainous regions of the states of Espirito Santo, Minas Gerais, Paraná, Rio de Janeiro, São Paulo and Santa Catarina. The pollen grains of eight species were acetolyzed and analyzed and photographed using light microscopy. Unacetolyzed pollen grains were analyzed and photomicrographed using scanning electron microscopy. The current study undertook a palynologically analysis of Graphistylis in order to obtain information useful for making a better ranking of these genus. The results show medium-sized pollen grains that were oblate spheroidal or prolate spheroidal and subtriangular amb and tricolporate. The pollen grains possessed lalongate endoapertures with a median constriction and the presence of costa in only two species. The exine is echinate with a varying number of spines in the apocolpium region around the central spine in polar view. The spines are short with basal perforations at varying distances. Although the morphology of the pollen of species ofGraphistylis is very similar, multivariate analysis highlights the importance of quantitative traits in distinguishing species. <![CDATA[To resist or to germinate? The effect of fire on legume seeds in Brazilian subtropical grasslands]]> Fire plays an important role in several grassland ecosystems in the world. Fire can trigger germination in several species, by breaking the physical dormancy of their seeds. Thus, we hypothesized that exposure to high temperatures during fire would break seed dormancy and enhance germination. We tested the effect of high temperatures on the germination of six species of legumes from Brazilian subtropical grasslands. We used heat shock experiments with the following treatments: 60, 90, 120 and 150ºC for one minute. Seeds were then placed to germinate for 60 days in 12/12 hours light/dark and 20/30ºC. Germination was generally low for all study species. Most species was not affected by heat shock treatments. However, Stylosanthes montevidensis was the only species that had its physical dormancy broken when exposed to 120ºC. The seeds of all the other species were neither stimulated nor killed by high temperatures. Although the exposure to high temperatures did not affect the germination of the study species (except for one), it also did not kill seeds, thereby showing that seeds are resistant to fire. Therefore, the rapid passage of fire in these grasslands is not sufficient to break the dormancy of most of the studied species of legumes. <![CDATA[Freeze tolerance differs between two ecotypes of Paspalum vaginatum (Poaceae)]]> Morphological and physiological responses to freezing were evaluated in two ecotypes of the perennial turfgrass Paspalum vaginatum. Leaf extension rate, number of active meristems, leaf water potential and net photosynthesis were measured on plants of both a commercial cultivar, 'Sea Isle 2000', and a wild ecotype from the Flooding Pampa grasslands of Argentina. Plants were propagated by cloning, cultivated in pots, and examined during 18 consecutive days under two treatments: a non-frozen control treatment (15.5±7 ºC) and a frozen treatment with two stages: Stage 1 with four hours of freezing stress for 10 nights (-5ºC), and Stage 2 with 12 hours of freezing stress for eight nights (five nights at -5ºC and three nights at -8ºC). After these treatments, plants were returned to the outside environment to evaluate shoot injury and post-freezing recovery. Leaf water potential, net photosynthesis and leaf extension rate were significantly higher in the wild ecotype than in the commercial cultivar. Meristem density was reduced after freezing in both ecotypes, but was more pronounced in the commercial cultivar (98.5%) than in the wild ecotype (80%). Thus, the two ecotypes coming from different environments, exhibited different morphological and physiological responses to exposure to freezing temperatures.