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The aim of this investigation was to analyze two samples of pollen from jandaira stingless bees (Melipona subnitida) in view of their mineral composition, free amino acids and sugars. Palynological analysis showed that the predominant pollen was monofloral from Senna sp. species (94.5%, pollen 2011) and the second pollen sample showed the presence of two primary species, Chamaecrista sp. (39.2% pollen 2009) and Mimosa tenuiflora (43.5%) (pollen 2009). The highest mineral content was potassium. The bee pollen contained 20.8% and 31.0% of mannitol in samples from 2011 and 2009, respectively. Proline and serine are the predominant amino acids. High content of essential amino acids, minerals and the sugar mannitol confirmed high nutritional value of pollen samples from jandaira bees.

The diversity of Fabaceae in Mexico has a long geological history, and it is particularly rich in sediments from the Oligocene and Miocene. In this work, we describe the first record of two woods resembling ?Cercidoidea and Dialonoidea subfamilies from the Eocene of Chiapas. Both fossil woods have medium to large vessels, abundant paratracheal axial parenchyma, simple perforation plates, short vessel elements, alternate intervessel pits and non-vestured, vessel–ray pits with distinct borders and similar to intervessel pits in size and shape, homocellular (slightly heterocellular) multiseriate rays, prismatic chambered crystals in axial parenchyma cells and in fibers. These characteristics support the inclusion of both woods in Fabaceae. The identification of this new fossil genus (Tzotziloxylon) within Leguminosae, as well as other that have been described earlier from other Eocene localities of Mexico (e.g., Inga, Chamaecrista, and Senna), supports the hypothesis that some genera of this family probably evolved in North America instead of arriving by dispersal from Asia or Africa during the Eocene time.

Legumes and some nodulation processes evolved about 55–60Ma. Since then they have radiated from their origin at either side of the Tethys seaway, to high latitudes in both the northern and southern hemispheres. In many cases this has involved different tribes and genera, and different nodule processes, but with the common feature that almost all legumes in the higher latitudes are potentially nodulated and, with the exception of some herbaceous species of Chamaecrista, nodulated caesalpinioid legumes are rare. This is not true of tropical regions where all three sub-families are found, with many of their species lacking the ability to nodulate. Whether or not this is related to the availability of combined nitrogen is a matter of current discussion. This review will consider the range of nodulation phenotypes (infection, morphology, structure) and show how many of these are confined to one or other hemisphere. How this might relate to the different genera and species of endophytic (nitrogen fixing) rhizobia in relation to soil conditions will also be discussed. Better knowledge of the wide variation in nodulation parameters is important for understanding the ecology of different regions and for management purposes. Nodule characters are of great potential use in defining taxonomic groupings in legumes.

† Background and Aims Reciprocal herkogamy, including enantiostyly and heterostyly, involves reciprocity in the relative positions of the sexual elements within the flower. Such systems result in morphologically and, since pollen is deposited on and captured from different parts of the pollinator, functionally distinct floral forms. Deviations from the basic pattern may modify the functionality of these mechanisms. For heterostylous species, such deviations are generally related to environmental disturbances, pollination services and/or reduced numbers of one floral morph. Deviations for enantiostylous species have not yet been reported. This study aims to investigate enantiostyly in Chamaecrista flexuosa, in particular the presence of deviations from the standard form, in an area of coastal vegetation in north-east Brazil. † Methods Observations and investigations of floral biology, the reproductive system, pollinator behaviour, floral morphology and morphometry were performed. † Key Results In C. flexuosa flowers, anthers of different size but similar function are grouped. The flowers were selfcompatible and set fruits after every treatment, except in the spontaneous self-pollination experiment, thereby indicating their dependence on pollen vectors. The flowers were pollinated by bees, especially Xylocopa cearensis and X. grisencens. Pollen is deposited and captured from the ventral portion of the pollinator’s body. Variations in the spatial arrangement of floral elements allowed for the identification of floral morphs based on both morphological and functional criteria. Using morphological criteria, morphologically right (MR) and morphologically left (ML) floral morphs were identified. Three floral morphs were identified using functional criteria: functionally right (FR), functionally central (FC) and functionally left (FL). Combinations of morphologically and functionally defined morphs did not occur in equal proportions. There was a reduced frequency of the MR‐ FR combination. † Conclusions The results indicate the occurrence of an atypical enantiostyly in C. flexuosa. This seems to improve reproductive success by increasing the efficiency of pollen deposition and capture.

Reintroduced environments represent stressful conditions to plants that can be observed in different ways. We evaluated the relationships between fluctuating asymmetry (FA), herbivory, and plant ontogeny of Chamaecrista semaphora (Fabaceae) under natural and restored habitat conditions. The patterns of leaf FA and herbivory by folivorous insects (chewing) on saplings and mature plants in each habitat were determined. No relationship was found between FA and herbivory on the two ontogenetic stages in both environments, suggesting that FA did not represent an indicator of stress. The frequency and amount of leaf area removed by folivores were higher in saplings compared to adult plants under the natural habitat, while the opposite trend was observed on restored habitat for adult plants. The restored habitat did not represent an environmental stress condition to C. semaphora, indicating that this endemic plant may represent a good candidate to restoration programs in harsh environments. However, we observed ...

The pollen spectra of 16 samples of geopropolis of Melipona fasciculata from three phytogeographic regions in Maranhao, Brazil, have been analysed. Samples GP1 to GP4 were collected in Palmeirândia located in the region of periodic flooded fields (lowlands of the northern micro-region of Maranhao). Samples GP5 to GP8 were collected in Barreirinhas (Cerrado vegetation, northern micro-region of Maranhao). Samples GP9 to GP16 were collected in Belagua (Restinga vegetation, eastern micro-region of Maranhao). Thirty-eight pollen types were identified, distributed in 26 families and 29 genera. The most frequent pollen types were Mimosa pudica, Mimosa caesalpiniifolia, Chamaecrista and Solanum. Eucalyptus, Psidium, Combretum/Melastomataceae, Arecaceae, Mauritia and Ardisia pollen types were present in variable amounts (‘accessory pollen’ and/or ‘isolated pollen’). Alternanthera, Amaranthaceae, Desmodium, Dioclea and Dalbergia pollen types occurred with a lower percentage (‘occasional pollen’). The first ...

The defensive role against seed predation of a set of plant traits in 13 congeneric sympatric taxa (Chamaecrista: Leguminosae), and the influence of the third trophic level on seed predators’ performance and host range were investigated. Taxa co-occur in rupestrian grasslands in Serra do Cipo, Brazil, and belong to three taxonomic sections. Fruit production, fruit pubescence, and seed size were analyzed. Measures of these traits in the 13 taxa were regressed separately against seed predation rates by endophagous and ectophagous insects. Time of seed production and fruit pubescence showed no influence on seed predation rates by either predator type. Seed size was positively correlated to bruchid seed predation, but negatively related to ectophagous seed predation. There was a negative correlation between glandular fruit trichome length and parasitism rates of bruchids, suggesting that seed predation pressure may have produced evolutionary responses from plants (fruit trichome reduction), which should facilitate parasitoid action.

The mating system of seven sympatric taxa of Chamaecrista occurring in the Chapada Diamantina Mountains, northeastern Brazil, was studied to determine the occurrence of self-incompatibility and interspecific genetic isolation mechanisms within the group. Self- and cross-pollination experiments and inter-taxon bidirectional crosses were performed. All of the populations were self-compatible and showed high percentages of spontaneous seed abortion on both self- and cross-pollinated fruits. The inter-incompatibility among the taxa of Chamaecrista is directed by different mechanisms depending on their degrees of phylogenetic proximity. In the crosses between closely related taxa (same clade), seed inviability was observed in the crossing pairs C. desvauxii var. graminea × C. desvauxii var. latistipula, and C. chapadae × C. glaucofilix. Inter-compatibility between species of the same clade occurred in C. blanchetii and C. confertiformis, with the formation of viable seeds. Pre-zygotic gametophytic reproductive isolation was observed among taxa of different clades, without penetration of the pollen tube into the ovule, or post-zygotic isolation through embryo or endosperm inviability, with abortion of the seeds. Inter-incompatibility represents an important factor in reproductive isolation and thus in the maintenance of the genetic identity of sympatric taxa that flower in synchrony and share pollinators.

Premise of the Study. The internal transcribed spacer (ITS) region is situated between 18S and 26S in a polycistronic rRNA precursor transcript. It had been proved to be the most commonly sequenced region across plant species to resolve phylogenetic relationships ranging from shallow to deep taxonomic levels. Despite several taxonomical revisions in Cassiinae, a stable phylogeny remains elusive at the molecular level, particularly concerning the delineation of species in the genera Cassia, Senna and Chamaecrista. This study addresses the comparative potential of ITS datasets (ITS1, ITS2 and concatenated) in resolving the underlying morphological disparity in the highly complex genera, to assess their discriminatory power as potential barcode candidates in Cassiinae. Methodology. A combination of experimental data and an in-silico approach based on threshold genetic distances, sequence similarity based and hierarchical tree-based methods was performed to decipher the discriminating power of ITS datasets on 18 different species of Cassiinae complex. Lab-generated sequences were compared against those available in the GenBank using BLAST and were aligned through MUSCLE 3.8.31 and analysed in PAUP 4.0 and BEAST1.8 using parsimony ratchet, maximum likelihood and Bayesian inference (BI) methods of gene and species tree reconciliation with bootstrapping. DNA barcoding gap was realized based on the Kimura two-parameter distance model (K2P) in TaxonDNA and MEGA. Principal Findings. Based on the K2P distance, significant divergences between the inter- and intraspecific genetic distances were observed, while the presence of a DNA barcoding gap was obvious. The ITS1 region efficiently identified 81.63% and 90% of species using TaxonDNA and BI methods, respectively. The PWG-distance method based on simple pairwise matching indicated the significance of ITS1 whereby highest number of variable (210) and informative sites (206) were obtained. The BI tree based methods outperformed the similarity-based methods producing well-resolved phylogenetic trees with many nodes well supported by bootstrap analyses. Conclusion. The reticulated phylogenetic hypothesis using the ITS1 region mainly supported the relationship between the species of Cassiinae established by traditional morphological methods. The ITS1 region showed a higher discrimination power and desirable characteristics as compared to ITS2 and ITS1+2, thereby concluding to be the locus of choice. Considering the complexity of the group and the underlying biological ambiguities, the results presented here are encouraging for developing DNA barcoding as a useful tool for resolving taxonomical challenges in corroboration with morphological framework.

Although most studies of mutualisms focus on a single partner at a time, host species often associate with multiple mutualist partners simultaneously. Because of potential interactions between mutualists, only studying a single type of mutualism could lead to a biased perspective of mutualism benefit and how mutualisms may scale-up to affect communities. The legume Chamaecrista fasciculata engages in a resource mutualism with nitrogen-fixing rhizobia and also forms symbiotic interactions with ants by providing nectar in exchange for defense against herbivores. Although they provide very different benefits to the plant, both mutualists receive carbon resources from the plant. As a result, these two mutualists are likely to interact, potentially competing for carbon resources or mutually benefitting each other via their positive effects on plant hosts. In a full-factorial field experiment, we explored how rhizobia and ants influence one another, C. fasciculata fitness, and the associated arthropod community. Ants reduced plant allocation to rhizobia, but ants also increased rhizobia contamination of uninoculated plants, suggesting that ants may disperse rhizobia. In turn, rhizobia increased ant abundances, with ants preferentially tending plants with rhizobia. Chamaecrista fasciculata received substantial fitness benefits from rhizobia; in contrast, associating with ants reduced fitness. Additionally, the mutualists interacted to influence the abundance of other arthropods found on the plants. Rhizobia increased arthropod abundances, likely because more nitrogen-rich leaf tissue was more attractive to arthropod herbivores, but ants negated these increases. As these results illustrate, multiple mutualists may interact, influencing each other’s abundance and the abundance of other community members.

The genus Chamaecrista comprises more than 330 species which are mainly distributed across tropical America, especially in Brazil (256 spp.), the main center of radiation. In this study, nodulation of herbaceous Chamaecrista species that are commonly found growing in different vegetation types in the north eastern Brazilian state of Bahia was assessed together with the diversity of rhizobia isolated from their root nodules. Genetic characterization of the isolates was performed using molecular markers to examine the phylogeny of their "core" (16S rRNA, ITS, recA, glnII, dnaK and gyrB) and symbiosis-related (nifH, nodC) genomes. Nodule morphology, anatomy and ultrastructure were also examined, as was the capacity of the isolates to form nodules on Chamaecrista desvauxii and siratro (Macroptilium atropurpureum). Analysis of 16S rRNA gene sequences demonstrated that the isolates belonged to seven clusters within the genus Bradyrhizobium, and more detailed analyses using sequences of the ITS region and concatenated housekeeping genes grouped the Chamaecrista rhizobia by vegetation type and plant species. These analyses also suggested some potentially novel Bradyrhizobium species, which was corroborated by analyses of their nifH and nodC sequences, as these formed separated branches from all Bradyrhizobium type strains. All the 47 strains tested produced effective nodules on C. desvauxii but none on siratro. Chamaecrista nodules are herein described for the first time in detail: they are indeterminate and structurally similar to others described in the Caesalpinioideae, with infection threads in the invasion and nitrogen fixation zones, and with both infected and uninfected (interstitial) cells in the nitrogen fixation zone.

Resumo Um checklist das espécies de Angiospermas provenientes do Parque Estadual de Itaúnas, Espírito Santo, Brasil é apresentado. As coletas foram realizadas quinzenalmente durante o período de 2012 a 2015 e as amostras botânicas estão depositadas no Herbário VIES. Os resultados estão apresentados em forma de lista com um total de 562 espécies distribuídas em 345 gêneros e 110 famílias com suas respectivas formas de vida: arbustos e árvores; ervas terrestres; trepadeiras; epífitas e hemiepífitas; ervas aquáticas, parasitas (holo- e hemi-) e micoheterótrofas (saprófitas). Fabaceae, Myrtaceae, Cyperaceae, Rubiaceae, Bromeliaceae, Apocynaceae, Orchidaceae, Poaceae, Bignoniaceae e Melastomataceae são as famílias mais ricas em número de espécies. Os gêneros Eugenia (16 spp.) (Myrtaceae), Passiflora (10 spp.) (Passifloraceae), Myrcia (9 spp.) (Myrtaceae), Cyperus (7 spp.), Chamaecrista (Fabaceae) e Miconia (Melastomataceae) (6 spp., cada) são os mais representativos. A maioria dos checklists anteriormente realizados para o Espírito Santo apresenta números subestimados para a diversidade taxonômica de plantas. Os resultados aqui evidenciados confirmam a enorme importância ecológica das restingas na Mata Atlântica do Parque Estadual de Itaúnas. Abstract This paper provides a floristic inventory of Angiosperms reported from Parque Estadual de Itaúnas, Espírito Santo, Brazil. The inventory was performed with fortnightly fieldwork from 2012 to 2015. The samples collected are available at the herbarium VIES. A checklist with 562 species, from 345 genera and 110 families is provided. Lifeforms categories were established: shrubs and trees; terrestrial herbs; herbaceous and woody climbers; epiphytes and hemiepiphytes; aquatic herbs, parasites (holo- and hemi-), and myco-heterotrophs (saprophytes). Fabaceae, Myrtaceae, Cyperaceae, Rubiaceae, Bromeliaceae, Apocynaceae, Orchidaceae, Poaceae, Bignoniaceae, and Melastomataceae presented the greatest species richness. The genera Eugenia (16 spp.) (Myrtaceae), Passiflora (10 spp.) (Passifloraceae), Myrcia (9 spp.) (Myrtaceae), Cyperus (7 spp.), and Chamaecrista (Fabaceae) and Miconia (Melastomataceae) (6 spp., each) presented the greatest species richness. Most of the previous checklists elaborated in the Espírito Santo state have underestimated plant species diversity. This floristic inventory confirms the ecological value of the restingas in the Atlantic Forest located at Parque Estadual de Itaúnas.

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.

RESUMO O objetivo deste estudo foi determinar a relação entre constante dielétrica e teor de umidade de seis espécies de madeira, por meio da construção de um capacitor. O material utilizado constituiu-se de madeiras da Amazônia não comercializadas, mas com alta abundância e dominância na Floresta Nacional deAlbizia duckeana (fava-paricá), Brosimumsp. (amapá-doce), Chamaecrista scleroxylon (pau-santo),Qualea dinizii (mandioqueira-rosa), Trattinnickia burserifolia (amescla) e Swartzia laurifolia(gombeira). Os corpos de prova para determinação da constante dielétrica foram confeccionados com as dimensões de 4,5 x 4,5 x 1 cm, definidas por testes preliminares realizados no Laboratório de Produtos Florestais (LPF). Para a coleta dos valores de capacitância, foi também construído um capacitor, utilizando multímetro digital, fios de cobre e placas de alumínio, sendo as medições realizadas em oito ocasiões, com intervalos de 1 h cada, durante o processo de secagem, que se iniciou na condição de massa saturada até atingir massa constante. A partir dos dados, foram ajustadas as curvas de regressão entre os valores de teor de umidade e constante dielétrica da madeira, as quais apresentaram forte correlação com as duas variáveis, mostrando a influência direta e proporcional do teor de umidade sobre a constante dielétrica. Em razão da inexistência de relação direta entre os dados de massa específica e constante dielétrica das espécies estudadas, sugere-se o desenvolvimento de novos estudos para melhor explicar a relação entre essas duas grandezas. ABSTRACT The objective of this study was to determine the relation between dielectric constant and the humidity of six species of wood, by the construction of a capacitor. The material used was non commercialized Amazonian wood, but with high abundance and domination in the National Forest of Tapajós - State of Para, such as: Albizia duckeana (fava-paricá), Brosimum sp. (amapá-doce), Chamaecrista scleroxylon (pau-santo), Qualea dinizii (mandioqueira-rosa), Trattinnickia burserifolia(amescla) and Swartzia laurifolia (gombeira). The samples used to determinate the dielectric constant were made with the dimensions of: 4.5 x 4.5 x 1 cm, defined by preliminary tests made at Forestry Products Laboratory (LPF). The values of capacitance were collected by the construction of a capacitor using a digital multimeter, copper wires, and aluminum plates; and the values were collected eight times with intervals of one hour, during the drying process, starting at saturated mass to constant mass. Therefore, with the collected data the regression curves were established between humidity values and the dielectric constant of wood, which showed a strong correlation between the two variables, showing the direct and proportional influence of the humidity over the dielectric constant. Due to the inexistence of direct relation between specific mass and dielectric constant of the studied species, we suggest new studies to explain the relation between those characteristics.

A new species, Chamaecrista truncata, from southeastern Brazil, is described, illustrated and compared to its putative closest relative, C. parvistipula. The new species belongs to Chamaecrista sect. Chamaecrista ser. Flexuosae which is characterized by asymmetrical leaflets with palmate venation, quadrangular stems and axillary peduncles. Additionally, the venation pattern of the leaflets and the different types of stipules observed within this series are shown.

The genus Chamaecrista originates from the dismembering of Cassia L., which was elevated to the level of subtribe Cassiinae, giving rise to Cassia sensu stricto, Chamaecrista, and Senna. Phylogenetic analysis has suggested that Cassiinae is not monophyletic. The relationships between its genera are not clear, because they sometimes appear close to Chamaecrista and Senna and at other times close to Senna and Cassia. We describe here development of the seeds of three species of Chamaecrista and compare our data with information published in the literature for Cassiinae and non-Cassiinae legumes. The ovules appear well conserved in Cassiinae, differing only in the length of the funiculus. In terms of seed development, the shape of the endosperm haustorium is similar in Senna and Chamaecrista. Chamaecrista shares more characteristics of its mature seeds with Senna than with Cassia. Chamaecrista and Senna have variable seed shapes, the presence of pleurograms, the absence of root cap primordia, a short epicotyl, and the cotyledonary mesophyll tends to be dorsiventral. These seed characteristics place Senna close to Chamaecrista and distance it from Cassia. We also observed characteristics unique to Chamaecrista, for example the occurrence of multiple pleurograms, a partially multiplicative seed coat, and the presence of embryonic colleters.

Summary1. Mutualisticinteractionsarecharacterizedbyconditionaloutcomesthatdependonboththebio-tic and the abiotic context. However, limited information is available on the factors that affect thestrengthofant–plantinteractionsamongsympatriccongenericspecies.2. We compared the benefits gained from attracting ants via extrafloral nectaries – i.e. loweredherbivory and increased seed set – of three co-occurring varieties in the Chamaecrista desvauxiicomplex (Leguminosae) in a cerrado area in Uberlaˆndia, Brazil. Using whole-individual exclusionexperiments, we tested the hypotheses (i) that the relative strength of those benefits is higher in thevariety with the largest extrafloral nectaries and (ii) that those benefits are conditional on the pres-enceofpredispersalseedpredators.3. Extrafloral nectaries are larger, produce more nectar and attract more ants in var. brevipes thanintheothertwovarietiesincludedinthestudy.Var.modestahasintermediate-sizednectaries,whileathird,undescribedvarietyhassmallnectaries,andbothattractrelativelyfewants.4. For var. brevipes, extrafloral nectary (EFN) removal significantly increased folivory and attackonfruitsbysuckinginsects,decreasingtherelativenumberofflowers,fruitsandseedsproducedperindividual.Fortheothertwovarieties,incontrast,anteffectswerereduced,andantsdidnotsignifi-cantly improve reproductive success. In addition, effects of EFN removal were less pronounced orabsentwhenseedpredatorswereexcludedfromfruitsofvar.brevipes.5. Synthesis. Weshowedexperimentallythatbenefitsfrominteractionsofthreeco-occurringvarie-tiesof Chamaecristadesvauxiiwithantsarecontext-dependentbothwithinandamongtaxa.Varia-tion in the strength of mutualisms among sympatric taxa may potentially reinforce ecologicalreproductiveisolationandcontributetodiversificationinthisgroup.Key-words: ant–plant interactions, Brazil, cerrado, exclusion experiment, extrafloral nectaries,indirect defences, Leguminosae, plant–herbivore interactions, reproductive success, sympatricvarietiesIntroduction

Enantiostyly (mirror-image flowers) is usually associated with buzz pollination. In buzz-pollinated flowers, pollen is released through terminal pores after bees vibrate the stamens. Several studies have evaluated the function of ‘buzzing’ in pollen release, but less attention has been paid to the effect of buzzing on pollen capture and deposition on stigmas. Evaluating the mechanism of pollen dispersion in buzz-pollinated flowers is important because it may affect mating patterns and reproductive success. In this study, we analysed the morphology of sexual organs (anther and stigma) using electron microscopy, and determined the relationship between sexual organ structure and pollen capture function through experimental manipulations of buzz-pollinated flowers of Chamaecrista chamaecristoides, as well as vibration frequencies on floral visitors. Pollen release occurs through two terminal pores at the tip of the stamens. However, unlike most angiosperms that have their stigmatic surface exposed, C. chamaecristoides presents a stigmatic surface inside a cavity covered by trichomes. Experimental manipulations showed that effective fertilisation is only achieved when the style is vibrated, suggesting that buzzing is not only important for pollen release but also for pollen capture and deposition on the stigma. This result, in addition to vibration frequency analysis, suggests that although all floral visitors buzz flowers only those that buzz at higher frequencies achieve effective fertilisation. The anatomical features of sexual organs in flowers of C. chamaecristoides demonstrate that this species possesses a highly specialised, elaborate morphology, with both genders selected for traits that promote buzz pollination.

Current evidence suggests that ant–plant relationships may influence species composition, abundance, and interactions at the community scale. The main resource that plants offer to ants is extrafloral nectar (EFN) and the major part of published studies shown benefits from ants to plants possessing EFNs. However, the complementary question of whether and how ants benefit from EFNs is rarely addressed. Here, we present the results of a long-term study to demonstrate whether EFN has a positive effect on ant colony fitness. We quantified colony growth rate, survival and the final weight of individuals as measures of benefit derived from EFN. Our results provide clear evidence that EFN can have a significant positive impact on the survivorship, growth and reproduction of the Myrmicinae Cephalotes pusillus. In fact, a diet rich in EFN (providing at least 30 cal per day) resulted in five times more individuals per colony, greater body weights, and more eggs. These results have shed new light on the relationships between ants and EFN-bearing plants such as in tropical and temperate systems. The ant C. pusillus is the first case in which we have firm evidence that EFN improves colony growth and development, corroborating more than 100 years of experimental evidence of benefits to plants in these widespread relationships.

Leguminosae é considerada a família mais diversa nas savanas de Roraima, que são as maiores áreas de savana da Amazônia brasileira. Este trabalho tem como objetivos fornecer uma listagem florística e analisar os padrões de distribuição geográfica dos táxons de Leguminosae encontrados em uma área de savana em Boa Vista, Roraima (02º52´07´´N; 60º43´03´´W). Foram registrados 80 táxons distribuídos em 38 gêneros. Seis táxons são novos registros para a flora de Roraima. Os gêneros que apresentaram o maior número de espécies foram Aeschynomene e Chamaecrista, cada um com sete espécies. Leguminosae-Papilionoideae foi a subfamília mais diversa em número de gêneros (24) e de táxons infragenéricos (53). A análise da distribuição geográfica revelou a predominância de táxons com padrão neotropical. A área estudada representa um sítio diverso em táxons de Leguminosae, pois concentra cerca de 87% da diversidade citada para a família nas savanas de Roraima.

Chamaecrista Moench is a genus of caesalpinioid legumes with about 330 species mostly from the New World. The phylogeny of the genus was studied using sequence data from nuclear ITS and plastid trnL-F DNA spacers, representing all six sections of Chamaecrista. Separate and combined analyses recovered the same major clades with high bootstrap and posterior probabilities support, except for the subclades of representatives of sections Caliciopsis, Chamaecrista, and Xerocalyx. The monophyly of Chamaecrista was highly supported in all analyses. Sections Apoucouita and Xerocalyx were supported as monophyletic, sect. Absus was paraphyletic and subsect. Baseophyllum was resolved more closely related to species of sections Chamaecrista, Caliciopsis, and Xerocalyx than to subsect. Absus. The monotypic section Grimaldia was embedded within subsect. Absus. Section Chamaecrista was paraphyletic with respect to sections Caliciopsis and Xerocalyx. Our analyses suggest that the diversification patterns in Chamaecrista occurred through an initial shift from rainforest trees to a more diverse clade of savannah shrubs. Within the latter group, two main subclades were recovered: (1) a planaltine and high-mountain clade characterized by absence of extrafloral nectaries and the appearance of sticky glandular hairs; and (2) a mostly herbaceous clade with axillary fascicled inflorescences and reduced chromosome numbers. This last group is more diverse in open grassland areas and includes many colonizers of waste ground.

Round leaf cassia (Chamaecrista rotundifolia) cv. ‘Wynn’, a species of leguminous forage, was introduced into China from the Australian Centre for International Agricultural Research in 1989. It possesses strong resistance to adversity and is suited for planting in the red soil area of Southern China. The purpose of this study is to investigate the effects of molybdenum (Mo) application with different concentrations on plant growth, molybdoenzyme activity and mesophyll cell ultrastructure of C. rotundifolia in red soil. The results showed that, plant height, number of branches, and dry matter weight of C. rotundifolia under varying Mo applications (0.5, 1.0, 2.0, 4.0 mg kg−1) increased by 2.7%∼11.5%, 0.92%∼28.68%, and 52.9%∼115.2% compared with the control group, respectively, and they all increased with the increase of Mo concentration. Molybdenum contents in plants were also increased significantly with increasing the concentration of Mo, but Mo contents in plants at 4 mg kg−1 Mo application we...

The increasing anthropogenic pressure in the rare rupestrian fields in southeastern Brazil has led to the expansion of degraded areas on the extremely nutrient-deficient quartzitic soils. On the other hand, the use of rupestrian field native species in reclamation programmes has been hampered by the lack of studies involving seedling physiological ecology. The present study evaluated biomass allocation and seedling growth rate during early seedling growth of four Fabaceae shrubs: Collaea cipoensis , Calliandra fasciculata , Chamaecrista ramosa , and Mimosa foliolosa . The following hypotheses were tested: (i) species proportionally allocate higher biomass to the roots, presenting a high root/shoot ratio; and (ii) species exhibit low phenotypic variation because they have adapted to poor nutritional environments. A 12-month greenhouse experiment was carried out to evaluate seedling growth and biomass allocation performance in substrates with contrasting levels of soil fertility. The four species studied presented values of root/shoot ratio lower than one in both fertility conditions of the substrate. Growth parameters for Collaea and Calliandra increased with increasing soil fertility, while no differences were observed for Mimosa and Chamaecrista . Although the four species are naturally adapted to low nutritional quality soils, seedling development was not hindered by high fertility substrate conditions. Despite the remarkable differences in fertility between the substrates, the responsiveness in growth and allocation in Chamaecrista and Mimosa was lower than that expected if the species would exhibit high phenotypic variation. The implications for rupestrian field restoration are discussed.

lack pleurograms and have pitted testas aligned in verticallines. Preliminary observations have revealed that these small structures consist of superficial alterations of thetesta that are coloured differently to the rest of the seed coat and stand out as pits. However, no anatomicalinspection has yet determined the precise composition of these pits. The present work examined the morphology,surface micromorphology, anatomy, and histochemistry of the seed coat of mature seeds of

The benefits of ant-plant-herbivore interactions for the plant depend on the abundance of ants and herbivores and the selective pressures these arthropods exert. In plants bearing extrafloral nectaries (EFN), different mean trait values may be selected for by different populations in response to local herbivore pressure, ultimately resulting in the evolution of differences in plant traits that attract ants as defensive agents against herbivory. To determine if variation in traits that mediate ant-plant interactions reflect herbivore selective pressures, we quantified intra- and inter-population variation in plant traits for eight populations of the EFN-bearing annual Chamaecrista fasciculata (Michx.) (Fabaceae). Censuses in rural and urban areas of Missouri and Illinois (USA) showed population differences in ant attendance and herbivore pressure. Seeds were collected from each population, and plants were grown in a common greenhouse environment to measure sugar production, nectar volume and composition, EFN size and time of emergence, leaf pubescence, and leaf quality throughout plant development. Populations varied mainly in terms of nectary size, sugar production, and nectar volume, but to a lesser degree in leaf pubescence. Populations of C. fasciculata within urban areas (low in insect abundance) had small nectaries and the lowest nectar production. There was a positive correlation across populations between herbivore density and leaf damage by those herbivores on the one hand and sugar production and nectar volume on the other. These results, in conjunction with lack of evidence for maternally based environmental effects, suggest that population differences in herbivore damage have promoted differential evolution of EFN-related traits among populations.

We carried out genetic and morphometric analyses in 33 populations belonging to all nine described and one putative taxa of Chamaecrista subsect. Baseophyllum. Genetic variability was low in all taxa. Morphological and genetic data are consistent with the status of C. depauperata and C. coriacea. However, divergence between C. cytisoides var. cytisoides and all the other six conspecific varieties is higher than the divergence between it and the other two species. Our data support the recognition of eight species in the subsection Baseophyllum. Chamaecrista coriacea and C. depauperata are supported in their original circumscription. However, the varieties ascribed to C. cytisoides are best treated as six different species. We propose five new combinations in order to raise varieties of C. cytisoides to specific rank: C. blanchetii, C. brachystachya, C. confertiformis, C. decora, C. unijuga. We also propose synonimization of one variety, C. cytisoides var. micrantha, under C. brachystachya.

Few previous studies have assessed the role of herbivores and the third trophic level in the evolution of local adaptation in plants. The overall objectives of this study were to determine (1) whether local adaptation is present in the ant-defended plant, Chamaecrista fasciculata, and (2) the contribution of ant-plant-herbivore interactions and soil source to such adaptation. We used three C. fasciculata populations and performed both a field and a greenhouse experiment. The first involved reciprocally transplanting C. fasciculata seedlings from each population-source to each site, and subsequently applying one of three treatments to one-third of the seedlings of each population-source at each site: control, reduced ant density and reduced folivory. The greenhouse experiment involved reciprocal transplants of population-sources with soil sources to test for a soil-source effect on flower production and local adaptation to soil conditions. Field results showed that ant and herbivore treatments reduced ant density (increasing folivory) and herbivore damage relative to controls, respectively; however, these manipulations did not impact C. fasciculata reproduction or the likelihood of survival. In contrast, greenhouse results showed that soil source significantly affected flower production. Overall, plants in both experiments, regardless of population-source, always had higher reproductive output at one specific site. Native populations did not outperform nonnative ones, causing us to reject the hypothesis of local adaptation. The absence of treatment effects on plant reproduction and the likelihood of survival suggest a limited effect of ants and folivores on C. fasciculata fitness and local adaptation during the study year. Temporally inconsistent effects of biotic forces across years, coupled with the young age of populations, relative proximity of populations and possible counter effects of seed predators may reduce the likelihood of local adaptation in the populations studied.

The Serra do Espinhaço in Brazil is under continuous and increasing levels of human disturbance. It has a large number of endemic plant species such as Chamaecrista semaphora (Irwin and Barneby), an endangered species with extremely narrow range. We studied the genetic diversity of C. semaphora and compared it with Chamaecrista mucronata (Spreng.) Irwin and Barneby, a widespread congeneric species distributed over the entire Serra do Espinhaço, in an attempt to provide information for conservation strategies. Two populations of C. mucronata and the only two known populations of C. semaphora from Serra do Cipó were screened for variability using random amplified polymorphic DNA (RAPD) markers. Populations of C. semaphora exhibited a lower percentage of polymorphic markers (16.9%) and Shannon’s Diversity Index (H′pop= 0.124) than C. mucronata populations (43.3% and H′pop= 0.299). Most of the genetic variability of both species studied was distributed within populations; C. semaphora populations (ΦST= 0.198) were less divergent than C. mucronata populations (ΦST= 0.378). The risk of extinction for C. semaphora is large owing to its low level of genetic diversity compared with its widespread congener and because of increasing habitat destruction. Both populations of C. semaphora urgently need protection to maximize the genetic diversity of this species and diminish further substantial loss within the populations.

A floristic inventory of the remnant pinelands of the U.S.D.A. Subtropical Horticultural Research Station at Chapman Field, Miami-Dade County, Florida was conducted from July 2002 to March 2003. From the two-hectare study site, 159 vascular plant species were documented. These included six ferns and fern allies, two conifers, and 151 angiosperms (representing 49 families and 124 genera). Of the 159 species, 118 are native to North America north of Mexico and 41 are non-native but naturalized. The families with the most species in the study area included Fabaceae (25 spp.), Poaceae (20 spp.), Asteraceae (15 spp.), and Euphorbiaceae (9 spp.). The best-represented genera were Chamaesyce (five spp.), Sida (four spp.), and five genera with three species each: Chamaecrista, Ipomoea, Lantana, Rhynchosia, and Senna. Five species are new records for Miami-Dade County. Ten Florida endemic species, eight Florida threatened species, four Florida endangered species, and one federally listed endangered species...

† Background and Aims Differences in the mating systems and the mechanisms of reproductive isolation between Chamaecrista desvauxii var. graminea and C. desvauxii var. latistipula were examined in the Chapada Diamantina, Brazil. These taxa occur sympatrically, and their populations demonstrate marked morphological differences. The objective of the present work was to determine if reproductive isolation mechanisms exist between these two populations of C. desvauxii, and to determine the influence of these putative mechanisms on their genetic differentiation. † Methods Field observations were made of floral biology, phenology and floral visitation, and experiments on intraand interpopulation pollination and germination rates of the resultant seeds were performed. A genetic examination of the populations was undertaken using four allozyme loci. † Key Results The varieties examined demonstrated overlapping of flowering periods during the months of June to September. The main pollinator for both varieties was the bee Bombus brevivillus. Both varieties are self-compatible, and a large number of fruits are formed in cross-pollinations with high seed germination rates. Inter-taxa pollinations result in high levels of fruit production, but no seeds are formed. Two of the four loci examined were diagnostic for the varieties, and exclusive high-frequency alleles were encountered at the other loci, leading to a high genetic distance between the two populations (0.495). † Conclusions Pre-zygotic barriers were not found between the two varieties, and these remain isolated due to postzygotic events. The two varieties demonstrate marked differences in their morphology, floral biology, phenology and genetic make-up, all of which indicate that they should be treated as two distinct species. A complete revision involving the other varieties of the C. desvauxii complex will be necessary in order to define these two taxa formally.

Cassia L. sensu lato, a large heterogeneous genus of flowering plants, occurs naturally in the tropics around the world. Recent works based on floral morphology have supported a division of this genus into three genera, namely Cassia L. s. str., Chamaecrista Moench and Senna Mill. In order to investigate this new classification, 508 specimens of 18 taxa of the genus Cassia s.l. grown in Thailand were analyzed using cluster analysis and canonical discriminant analysis. The total 32 vegetative and reproductive morphological characters were employed in these analyses. In cluster analysis, Cassia s.l. can be separated into four groups, respectively viz. Chamaecrista, Senna alata, Senna and Cassia s /str. The four-cluster grouping is discussed. From a canonical discriminant analysis using the four-cluster grouping as a priori groups, it can be concluded that Cassia s. str., Senna, and Chamaecrista are indeed distinct taxa. The three most important characters that separate the three genera are filament length, fruit length, and ovary stalk length. These quantitative characters, together with some qualitative characters, were useful in constructing an identification key to these genera. Among the three genera, it was also found that Senna is rather a heterogeneous taxon. The difference between the studied species was discussed.

Conservation of species of concern in fire-dependent ecosystems requires restoring the historical fire regime that has shaped the species' life history. The historical fire regime of the endangered pine rockland ecosystem is controversial. In this study, we attempted to infer the historical fire regime of this ecosystem by studying the effects of contrasting experimental fire regimes on Chamaecrista keyensis, a narrowly endemic species of the pine rocklands of the Lower Florida Keys, USA. We constructed multiple matrix population models for C. keyensis using demographic data from replicated wet- and dry-season burns, 1–30 years since fire, and seed bank dynamics derived from extensive field seed bank experiments. We then carried out deterministic analyses and stochastic simulations. Recently burned sites (1–2 years postfire) had the highest finite population growth rates of all sites. Differences in finite population growth rate between winter and summer fires were more pronounced during the year of burn ...

Cloudless sulphur larvae (Phoebis sennae, Pieridae) were observed in an experimental plantation and also in a natural setting being fed on by the ectoparasitic biting midge, Forcipomyia (Microhelea) eriophora (Williston) (Diptera: Ceratopogonidae). Larvae parasitized by midges died at higher rates in captivity, in contrast to normal levels of mortality in rearings of this species, providing circumstantial evidence for the potential role of these flies in disease transmission.

Despite the abundance of woody legumes in Brazilian Amazonian rain forests, there are few chromosome counts on the native species of this important region. The present work presents such data for 13 species of Caesalpinioideae (the genera Bauhinia, Caesalpinia, Cassia, Chamaecrista and Senna) and Papilionioideae (Bowdichia, Centrosema and Dioclea) collected from 17 natural populations. Our report represents the first chromosome counts for the genera Bowdichia and Dioclea and for four of the studied species. Observations are made on chromosome morphology, size, condensing behaviour and interphase nucleus structure. Banding with fluorochromes carried out for the first time in Caesalpinioideae revealed discrete CMA+/DAPI– terminal (GC-rich) bands on 2–4 chromosome pairs of most species analysed, with a few species presenting discrete CMA–/DAPI+ (AT-rich) bands. Significant differences in chromosome size, morphology and condensing behaviour were observed among members of the controversial tribe Cassieae (Cassia, Chamaecrista and Senna), revealing the tribe to be a heterogeneous group from the karyological point of view. © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society, 2004, 144, 181–191.

We analyzed spatial plant-plant associations (during three seasons: nortes, dry, and rainy) and performed a field experiment on seedling survival, in order to test whether the occurrence of facilitation varied in response to seasonal weather fluctuations and to benefactor size. In a mobile dune system (central Gulf of Mexico) we focused on the endemic early colonizer shrub Chamaecrista chamaecristoides and two late colonizer bunch grasses. Total shrub cover and density were highest during the rainy period. Density of adult Trachypogon plumosus, but not that of adult Schizachyrium scoparium, was higher beneath the canopy of the shrub. No seasonal variations in spatial associations were observed. Density of grass seedlings decreased during the nortes beneath and beyond the canopy of C. chamaecristoides. Fitness parameters of both grasses improved beneath the benefactor plants, while sand accretion decreased. The number of grass individuals benefiting from facilitation increased with shrub size exce...

In a search for botanical products to control the main insect pest of stored cowpea, Callosobruchus maculatus, 33 traditionally used African plants were tested in the laboratory for their toxic and repellent effects against this beetle. Toxicity was evaluated measuring life history parameters in a no-choice situation. Powders of Nicotiana tabacum, Tephrosia vogelii and Securidaca longepedunculata significantly reduced the number of progeny. Repellence was evaluated by observing the behaviour of female beetles exposed to treated and untreated beans in a linear olfactometer. Clausena anisata, Dracaena arborea, T. vogelii, Momordica charantia and Blumea aurita were repellent to the beetle, whereas Chamaecrista nigricans, Azadirachta indica and Hyptis suaveolens were attractive. Our results indicate that botanical products may provide effective control of C. maculatus in cowpea.

This paper describes an assessment of the effect of exposure to fire-related cues (heat shock, smoke and nitrate) and the interactions between the cues on seed dormancy release of tropical savanna legumes in north-eastern Australia. Ten legume species were tested, comprising both native and exotic species. The ten species responded variously to the treatments. Brief exposure to temperatures between 80 and 100°C was found to break the seed dormancy of the native ephemeral herbs Chamaecrista mimosoides, Crotalaria calycina, Crotalaria montana, Indigofera hirsuta and Tephrosia juncea, as well as the exotic ephemeral herb Crotalaria lanceolata. Exposure to 80°C combined with treatment with a nitrate solution produced an additive effect on the germination of Chamaecrista mimosoides and Crotalaria lanceolata. However, the four species with the heaviest seeds, two exotic ephemeral herbs (Chamaecrista absus and Crotalaria pallida) and two native perennials (Galactia tenuiflora and Glycine tomentella) displayed no significant increase in germination with exposure to fire-related cues. Exposure to 120°C for 5 min produced seed mortality in all species tested. Two of the largest seeded species, Crotalaria pallida and Galactia tenuiflora, displayed the lowest tolerance to heat shock, with seed mortality after exposure to 100°C for 5 min. These data indicate that fire can promote the germination of some tropical savanna legumes. As a proportion of seeds of each species displayed no innate dormancy, some germination may occur in the absence of fire, especially of exotic species.

A revision of flower visitation records by bees of the genus Centris in the Caatinga, the xerophylous vegetation predominant in the semi-arid Northeastern Brazil, is presented. This revision includes, besides literature data, results from six annual surveys of the bee fauna and visited flowers, undertaken in limited areas of the States of Paraiba, Bahia and Rio Grande do Norte, Brazil. A total of 21 species of Centris were registered in these surveys, the highest species richness was observed in Castro Alves and Itatim (Bahia), 12 and 10 species, respectively. The higher species richness probably results from the presence of elements in adjacent biomas, since these two places are close to the eastern limit of the Caatinga. A total of 69 species of visited plants were registered. Caesalpinia pyramidalis (Caesalpiniaceae) and Melochia tomentosa (Sterculiaceae) are important nectar sources, as indicated by the higher number of Centris visitors' and by the number of areas where they occurred. Species of Chamaecrista, Senna (Caesalpiniaceae), and Solanum (Solanaceae) seem to be important pollen sources. Chamaecrista nictitans and C. pascuorum are registered for the first time as pollen sources for Centris hyptidis. The oil sources registered in the Caatinga for Centris bees belong to the families Malpighiaceae and Scrophulariaceae. Among the more abundant species of Centris, those not restricted to the Caatinga region (C. fuscata, C. aenea, C. tarsata and C. trigonoides) present a high similarity in the spectrum of visited plants. C. hyptidis, an endemic species, has a somewhat distinct niche.

An extensive allozyme survey was conducted within a natural ''meta'' population of the native North American annual legume, Chamaecrista fasciculata (Leguminosae) to quantify genetic structure at different spatial scales. Gene flow was then estimated by a recently developed indirect method based on a continuous population model, using pairwise kinship coefficients between individuals. The indirect estimates of gene flow, quantified in terms of neighborhood size, with an average value on the order of 150 individuals, were concordant among different spatial scales (subpopulation, population, metapopulation). This gene-flow value lies within the range of direct estimates previously documented from observations of pollen and seed dispersal for the same metapopulation. Monte Carlo simulations using the direct measures of gene flow as parameters further demonstrated that the observed spatial pattern of allozyme variation was congruent with a model of isolation by distance. Combining previously published estimates of pollen dispersal distances with kinship coefficients from this study, we quantified biparental inbreeding relative to either a single subpopulation or the whole metapopulation. At the level of a neighborhood, little biparental inbreeding was observed and most departure from Hardy-Weinberg genotypic proportions was explained by self-fertilization, whereas both selfing and biparental inbreeding contributed to nonrandom mating at the metapopulation level. Gene flow was also estimated from indirect methods based on a discontinuous population structure model. We discuss these results with respect to the effect of a patchy population structure on estimation of gene flow.

Periodic sampling of bees visiting flowering plants resulted in the collection of 91 individuals of 10 Centris species in an area of Caatinga (Itatim, Bahia, Brazil). These bees visited 12 species of plants. Melochia tomentosa (Sterculiaceae), a nectar source, was the most frequently visited plant. Chamaecrista, Senna and Solanum species were visited for pollen, and Stigmaphyllon auriculatum for oil. Centris bees were captured from September through April. The data suggest a seasonal pattern of activity, associated with the rainy season.

Facilitation is predicted to occur on coastal sand dunes as these ecosystems have the harsh physical conditions common during primary succession. In a tropical dune system on the Gulf of Mexico the spatial patterns of plant distribution were analyzed and the hypothesis that facilitation is the responsible mechanism was tested by monitoring changes in the micro-environment and performing a seedling planting experiment under natural conditions. Densities of seedlings and adults of late colonizer grasses were two to six times greater beneath the early colonizer shrub, Chamaecrista chamaecristoides, than in the exposed areas. Temperatures on the sand surface, wind speed and sand accretion were significantly reduced by the shade of Chamaecrista. Only phosphate contents during the dry season were significantly higher in sand in the shade than in exposed sand. In the field experiment, successful establishment of seedlings of two late colonizer grasses (Trachypogon plumosus and Schizachyrium scoparium) was low but was concentrated exclusively beneath the shrubs. The introduced plants were reproductive one year after onset of the experiment and remained vigorous after three years. The observed spatial aggregation among the target species may be a result of improved conditions in the shade of the shrub, which facilitated the survival and establishment of late colonizers. On top of the environmental amelioration, protection from recurrent disturbances such as substrate mobility is an additional beneficial effect of the shrub.

Previous research has demonstrated a positive rotational effect of tropical leguminous cover crops on maize growth on a luvisol from Nigeria. This effect could not be explained by a better N supply. The objective of the present work was to further clarify whether improved P nutrition has been a contributing factor. Nine cover crops and maize were studied in nutrient solution-culture with 1 and 20 μM P and with NO3-N as N source for root physiological parameters that may affect P mobilization. Zea mays, Lablab purpureus, and Centrosema pubescens responded to P deficiency by higher rates of proton excretion. Clitoria ternatea excreted OH— with only small differences due to P nutrition. At low P supply, Chamaecrista rotundifolia, Clitoria, and Centrosema had the highest exudation rates of organic acid anions, especially citrate and malate. A major difference between plant species was found in root-surface acid phosphatase activity. Cajanus cajan expressed the highest phosphatase activity. Vmax of P uptake increased markedly under P deficiency, particularly for maize. Compared to the other plant species Cajanus, Chamaecrista, and Clitoria were characterized by a greater capability to absorb P at low external P concentrations. The nine cover crops and maize were also grown in pot experiments using two soils from northern Nigeria low in available P. The ultisol from Jos had a high P fixation capacity and was more acidic than the alfisol from Zaria. All plant species were precultured in the first season at 100 (Zaria) and 250 (Jos) mg P per pot. In the subsequent season, maize was uniformly seeded into all pots containing the remaining roots and the incorporated shoot dry mass (according to 15 mg P per pot) of the pre-crop. No P and 250 (Zaria) or 500 (Jos) mg P per pot were freshly applied. Maize growth and P uptake were enhanced after legumes in Zaria soil. Cajanus showed the highest residual effect, and also Clitoria, Chamaecrista, and Lablab showed effects superior to the mean. In Jos soil, Clitoria, Cajanus, and Lablab enhanced maize growth above average. Also, a highly significant positive correlation between P uptake and biomass production was obtained. These results indicate that enhancement of maize growth after leguminous cover crops, at the low P supply of the soil used, mainly depends on P mobilization capacity of the cover crop. Mobilisierung von P ist mitverantwortlich fur die positive Vorfruchtwirkung von Leguminosen im Maisanbau auf Boden in Nord-Nigeria In vorhergehenden Untersuchungen konnte eine positive Vorfruchtwirkung von tropischen Leguminosen im Maisanbau auf einem Luvisol in Nord-Nigeria gezeigt werden. Diese Wirkung war unabhangig von der N-Versorgung. Ziel der hier dargestellten Versuche war es, weitergehend zu klaren, ob eine verbesserte P-Versorgung mitverantwortlich fur die positive Vorfruchtwirkung der Leguminosen zu Mais war. Neun Leguminosen und Mais wurden in Nahrlosungskultur mit 1 oder 20 μM P und NO3— als N-Quelle im Hinblick auf wurzelphysiologische Parameter der P-Effizienz charakterisiert. Zea mays, Lablab purpureus und Centrosema pubescens reagierten auf P-Mangel mit einer erhohten Abgabe von Protonen. Clitoria ternatea schied OH— aus, bei nur geringen Unterschieden in Abhangigkeit vom P-Angebot. Chamaecrista rotundifolia, Clitoria und Centrosema zeigten bei P-Mangel die hochste Ausscheidungsrate von organischen Saureanionen, insbesondere Citrat und Malat. Grose Unterschiede bestanden zwischen den Pflanzenarten in der Phosphatase-Aktivitat an der Wurzeloberflache. Cajanus cajan zeigte die hochste Phosphatase-Aktivitat. Die maximale P-Aufnahmerate (Vmax) war bei P-Mangel deutlich erhoht, insbesondere bei Mais. Cajanus, Chamaecrista und Clitoria zeichneten sich im Vergleich zu den anderen Pflanzenarten durch eine grosere Fahigkeit aus, P bei niedrigen Konzentration der Ausenlosung aufzunehmen. Die neun Leguminosen und Mais wurden auch in Gefasversuchen mit zwei P-armen Boden aus Nord-Nigeria kultiviert. Der Ultisol aus Jos wies eine wesentlich hohere P-Fixierungskapazitat und einen niedrigeren pH-Wert auf als der Alfisol aus Zaria. Alle Pflanzenarten wurden im ersten Jahr bei einem P-Angebot von 100 (Zaria) oder 250 (Jos) mg P pro Gefas kultiviert. Im zweiten Jahr wurde einheitlich Mais in den Gefasen mit den verbliebenen Wurzelruckstanden und eingearbeiteter Sprosstrockenmasse der Vorkultur (entsprechend 15 mg P pro Gefas) angebaut. Kein P bzw. 250 (Zaria) oder 500 (Jos) mg P pro Gefas wurden frisch appliziert. Im Boden aus Zaria waren das Wachstum und die P-Aufnahme von Mais nach Leguminosenvorfrucht verbessert. Cajanus wies die beste Vorfruchtwirkung auf, auch Clitoria, Chamaecrista und Lablab wirkten sich uberdurchschnittlich positiv aus. Im Boden aus Jos forderten insbesondere Clitoria, Cajanus und Lablab das Wachstum von Mais. Zwischen der P-Aufnahme und der Biomassenbildung von Mais bestand eine hoch signifikante positive Korrelation. Die Ergebnisse zeigen, dass die positive Vorfruchtwirkung von den verwendeten Leguminosen bei niedrigem P-Angebot des Bodens insbesondere von deren P-Mobilisierungsvermogen abhangt.

Plants growing on the beach are exposed to substrate mobility, freshwater inundation, and immersion in seawater, which greatly affect germination and species spatial distribution. In greenhouse experiments, we tested whether the most abundant species on the beach at La Mancha (on the Gulf of Mexico) were tolerant to burial and flooding. We buried seeds of Canavalia maritima, Ipomoea pes-caprae, Chamaecrista chamaecristoides, Palafoxia lindenii, and Ambrosia artemisiifolia at different depths. We used fresh- and seawater flooding with two frequencies: permanent and intermittent. The hard-coated seeds of Canavalia, Ipomoea, and Chamaecrista were left scarified and not scarified to test if dormancy was broken by the flooding regimes. Germination decreased as burial depth increased. We calculated a tolerance index for the burial responses, which indicated that Chamaecrista was the most tolerant species, followed by Canavalia and Palafoxia. Flooding inhibited germination, but more so permanent seawater flooding; it was especially lethal for species closest to the ocean such as Canavalia and Ipomoea. After transfer to freshwater, seeds of Chamaecrista, Palafoxia, and Ambrosia germinated. There was no evidence that hard-coat dormancy was broken by flooding. Tolerance to burial seems to be related to the spatial distribution of species but not to germination responses to flooding.Key words: germination, sand burial, freshwater, seawater, flooding, Gulf of Mexico.

We investigated the potential role of a nitrogen-fixing legume in facilitating invasion by an alien grass, Pennisetum setaceum (fountain grass) into native Heteropogon contortus grasslands in Hawai'i. Both grasses are C4 perennials. Many formerly extensive Heteropogon grasslands have been reduced to remnants surrounded by Pennisetum. An inconspicuous annual legume, Chamnaecrista nictitans (partridge pea), was commonly associated with Pennisetum stands but was found at higher densities in Pennisetum-Heteropogon mixtures. In the field, we also found higher exchangeable soil nitrogen beneath Chamaecrista-Pennisetum-Heteropogon mixtures than beneath neighboring pure Heteropogon stands. We then used greenhouse experiments to test the hypothesis that increased nitrogen facilitates Pennisetum's invasion of established Heteropogon. Under low nitrogen conditions, Pennisetum seedlings planted beneath established Heteropogon plants grew very little ( < 0.3 g biomass after 16 weeks), and their growth was not affected by high or low water treatments. In contrast, under high nitrogen conditions, in both low and high water treatments, Pennisetum seedlings grew rapidly, averaging 60 fold the biomass of seedlings in the low nitrogen treatment and exceeding the biomass of the established Heteropogon plants under which they were planted. We also compared Pennisetum-Heteropogon seedling competition in the presence and absence of live Chamaecrista. The growth of Pennisetum was not directly facilitated by live Chamaecrista in the greenhouse pots, but the Chamaecrista did not increase available soil nitrogen until after it had died. Our results suggest that increases in soil nitrogen, like those associated with an inconspicuous alien legume, can facilitate an alien grass' invasion of a native grassland.