Psychotria hoffmansegiana (Willd ex Roem. & Schult.) Mull. Arg. and Palicourea marcagravii st. Hil. (Rubiaceae): potential for forming soil seed banks in a brazilian Cerrado

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Morphological patterns of extrafloral nectaries in woody plant species of the Brazilian cerrado

Extrafloral nectaries are nectar-secreting structures that are especially common among the woody flora of the Brazilian cerrado, a savanna-like vegetation. In this study, we provide morphological and anatomical descriptions of extrafloral nectaries (EFNs) occurring on vegetative and reproductive organs of several plant species from the cerrado, and discuss their function and ecological relevance. We describe the morphology and anatomy of EFNs of 40 species belonging to 15 woody families using scanning electron microscopy and light microscopy. We categorise EFNs following a structural-topographical classification, and characterise the vascularised and complex nectaries, amorphous nectaries and secretory trichomes. Fabaceae, Bignoniaceae, Malpighiaceae and Vochysiaceae were the plant families with the majority of species having EFNs. Ten species possess more than one morphotype of gland structure. Observations and experimental field studies in the cerrado support the anti-herbivore role of EFN-gathering ants in this habitat. Additional morphological studies of EFNs-bearing plants, including other growth forms (e.g. herbs and lianas), are being undertaken and will hopefully cast further light on the ecological relevance of these glands in the cerrado, especially with respect to their attractiveness to multiple visitors.

Microhabitat selection and daily movements of two rodents (Necromys lasiurus and Oryzomys scotti) in Brazilian Cerrado, as revealed by a spool-and-line device

Studies on patterns of habitat use by mammals are necessary for understanding the mechanisms involved in their distribution and abundance. In this study, we used the spool-and-line method to investigate habitat utilization by two sigmodontine rodents from Brazilian Cerrado, Necromys lasiurus and Oryzomys scotti. We conducted the study in a Cerrado area in central Brazil (15 degrees 56'S and e 47 degrees 56'W) where the animals were caught in an area of 7.68 ha of Cerrado sensu stricto. Captured individuals were marked, equipped with a spool-and-Line device, and released at the same capture point. The next day we followed the thread to record their daily movements and find their nests. To investigate microhabitat selection we compared habitat characteristics along traits of each studied species with general habitat characteristics of the study area. Although the mean 24-h distance was greater for N. lasiurus (mean +/- SE: 41.9 +/- 42.2 m, N=3) than for O. scotti (28.7 +/- 14.2 m, N=6) this difference was not significant (Mann-Whitney test, U=26, P>0.6). We detected significant differences among observed microhabitats variables of both species and available microhabitat characteristics as determined by discriminant analysis (Wilks's lambda F=3.001; df=14, 116; P<0.001). Both species were associated to microhabitat characteristics whose values differed markedly from the overall available habitat. Along the first canonical discriminant function of the DFA both them were associated with greater grass height than the mean height available and along the second axis N. lasiurus selected areas with higher fruit availability and more shelters than those selected by 0. scotti. For stronger inferences regarding differential patterns of habitat utilization by Cerrado rodents we suggest the simultaneous use of both spool-and-line and standard trapping methods. (c) 2005 Deutsche Geseltschaft fur Saugetierkunde. Published by Elsevier GmbH. ALL rights reserved.

A simple graphical model of small mammal succession after fire in the Brazilian cerrado

We studied the succession of small mammal species after fire in the cerrado (Neotropical savanna) of Central Brazil. Populations of small mammals were sampled with live-trapping techniques in a series of nine sites of different successional age, ranging from 1 to 26 years after fire. Ten species of small mammals were captured through all the seral stages of succession. Species richness ranged from two to seven species by seral stage. The species were arranged in different groups with respect to abundance along the succession: the first was composed of early successional species that peaked <2 years after fire (Calomys callosus, C. tener, Thalpomys cerradensis, Mus musculus, Thylamys velutinus); the second occurred or peaked 2-3 years after fire (Necromys lasiurus, Gracilinanus sp., Oryzomys scoth). Gracilinanus agilis peaked in the last seral stage. Species richness of small mammals showed an abrupt decrease from an average of four species immediately after fire to two species 5-26 years after the last fire. We propose a simple graphical model to explain the pattern of species richness of small mammals after fire in the cerrado. This model assumes that the occurrence of species of small mammals is determined by habitat selection behavior by each species along a habitat gradient. The habitat gradient is defined as the ratio of cover of herbaceous to woody vegetation. The replacement of species results from a trade-off in habitat requirements for the two habitat variables.

Protease inhibition activity of extracts from Salicaceae species from Brazilian Cerrado and Atlantic Rain Forest and of an enriched fraction of clerodane diterpenes (casearins)

Considerando o uso popular de Casearia sylvestris Sw., Salicaceae, para o tratamento de problemas gástricos e resultados pré-clínicos que mostraram potencial atividade anti-ulcerogênica, foi realizado um screening farmacológico para avaliar a atividade biológica de outras espécies de Salicaceae. Para isso, foi utilizado um ensaio de inibição de proteases como um modelo farmacológico molecular para screening de extratos com atividade anti-ulcerogênica. Os extratos etanólico e aquoso dos galhos e folhas de C. gossypiosperma, C. decandra e C. rupestris mostraram inibição da atividade da pepsina em aproximadamente 50% com a concentração de 1 μg/mL. Curiosamente, C. obliquoa e Flacourtia ramontchi não apresentaram atividade sobre a pepsina, mas seus extratos mais apolares mostraram atividade inibitória sobre a subtilisina. A fração enriquecida de diterpenos clerodânicos mostrou atividade inibitória (42,75%) sobre a pepsina com a concentração de 1 μg/mL, mas não sobre a subtilisina (23,76%). Os resultados obtidos com os extratos e folhas das espécies testadas mostraram um padrão de atividade diferente sobre os dois tipos de proteases, a pepsina e a subtilisina, as quais estão relacionadas com diferentes tipos de atividades biológicas. Ainda mais, os resultados com a fração enriquecida de diterpenos clerodânicos sugerem que estas substâncias podem estar relacionadas com a atividade do extrato bruto de C. sylvestris.

Crab spiders (Araneae: Thomisidae) in flowering plants in a Brazilian Cerrado ecosystem

Ainda que aranhas Thomisidae sejam comumente encontradas em flores, as associações desses aracnídeos a espécies de plantas e às suas características florais foram pouco registradas na região neotropical. Observações do hábito das plantas, visitantes florais, e também das características florais, tais como antese, odor, forma, cor e recursos da flor, foram assinaladas para espécies floridas de uma área de cerrado presentes em uma trilha de 2 km de extensão. Misumenops argenteus e Misumenops pallens representaram 62,86% das aranhas habitantes de 22 espécies de plantas floridas. As plantas Senna rugosa (Fabaceae), Styrax ferrugineus (Styracaceae) e Banisteriopsis campestris (Malpighiaceae) abrigaram, individualmente, cerca de 10 a 17% do total das aranhas e, nestas plantas, a antese diurna; flores de coloração atrativa a abelhas, como amarela (S. rugosa), branca (S. ferrugineus) e rosa (B. campestris) e as anteras poricidas, bem como a visita das flores por abelhas reforçou a evidência de síndrome de polinização para melitofilia. Este é o primeiro levantamento de espécies de aranhas Thomisidae associadas a plantas do cerrado brasileiro.

Edge effect and phenology in Erythroxylum tortuosum (Erythroxylaceae), a typical plant of the Brazilian Cerrado

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Leaf heliotropism in Styrax camporum Pohl from the Brazilian cerrado: distinct gas exchange and leaf structure, but similar leaf temperature and water relations

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

In vitro anti-Mycobacterium tuberculosis activity of some Brazilian Cerrado plants

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Genetic variability in natural populations of Zeyheria montana mart. from the Brazilian Cerrado

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Antifungal activity of extracts from Brazilian Cerrado plants on Colletotrichum gloeosporioides and Corynespora cassiicola

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

EVOLUTION PATTERNS OF THE SOIL ORGANIC-MATTER IN SOME AGRICULTURAL SYSTEMS IN THE BRAZILIAN CERRADO REGION

Several changes in the soil humus characteristics were observed after clearing the Central Brazil virgin forest. When compared with the original ''Cerrado'' forest, the soils from the agricultural systems showed increased values for cation exchange capacity, total organic matter and non-extractable humin. The humic acid fraction underwent some changes suggesting increased oxidation and decreased aliphatic content. The soil organic N tends to accumulate in the insoluble humus fractions.The above changes were much less intense when the virgin forest was transformed into pastures. Under these conditions, the most significant changes were the reduction of readily biodegradable soil organic matter fractions.In view of the intensity of the lixiviation processes in the area studied, the above changes may be connected with the reduction in aggregate stability observed in the cleared sites.In general, the characteristics of the humus formations in the ''Cerrado'' region suggested high resistance to external factors, which is in part attributed to the active insolubilization of humic colloids by the Al and Fe oxides. In the absence of erosive processes in the cleared sites, additional humus stability may conform both to selective biodegradation and/or lixiviation of the humic colloids, or to the effects of the fire used in soil management.

Cytotoxicity of Active Ingredients Extracted from Plants of the Brazilian "Cerrado"

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)