Comparative wood anatomy of Caryocar brasiliense Camb. (Caryocaraceae) occurring in “cerradão” and “cerrado” sensu stricto formations

Este trabalho verificou a influência das condições ambientais na estrutura do xilema secundário da espécie Caryocar brasiliense Camb. (pequizeiro) através de um estudo anatômico comparado do lenho de árvores procedentes de fisionomias de cerradão e cerrado s.s., no município de Santa Rita do Passa Quatro, SP. As características do lenho foram analisadas qualitativa e quantitativamente, sendo as últimas comparadas pela análise de variância, bem como por análises multivariadas de agrupamentos e componentes principais. A análise de variância demonstrou existir diferenças significativas para oito das dezesseis variáveis analisadas, bem como uma grande variação entre árvores da mesma localidade, aspecto corroborado pela análise de agrupamentos. A matriz de correlação entre variáveis indicou, de modo geral, relações inversas entre dimensões longitudinais e radiais dos elementos anatômicos. Pode-se inferir pela variabilidade significativa entre árvores que a diferenciação das fisionomias ocorre de forma gradual, não se observando um conjunto de características anatômicas suficientemente marcantes que tipifiquem as fisionomias estudadas. _________________________________________________________________________________________ ABSTRACT: This study aimed to verify the influence of ambient conditions on the structure of secondary xylem of Caryocar brasiliense Camb. (“pequizeiro”) through a comparative anatomical study of two populations belonging to “cerradão” and “cerrado s. s. ” (Brazilian savannas), in the city of Santa Rita do Passa Quatro, São Paulo. The wood was described qualitatively, and quantitative data were analyzed using analysis of variance, as well as multivariate and principal components analysis. The analysis of variance showed significant differences for eight out of sixteen anatomical parameters, as well as great variation between trees of the same locality, an aspect corroborated by multivariate analysis. The correlation matrix showed generally inverse correlations between longitudinal and radial measurements of the anatomical characters. Based on the significant variability found between trees we can infer that the differentiation of the formations occurs gradually, since a marked set of anatomical characters that would individualize each type of vegetation was not observed

Algoritmo Genético Aplicado à Análise de Fatores de Risco Associados à Incidência da Malária, no Município de Augusto Corrêa – Pará, Brasil, em 2005

Este artigo apresenta resultados parciais de um projeto de desenvolvimento de um modelo aplicado à análise de fatores de riscos associados à incidência da malária no município de Augusto Corrêa – Pará, Brasil, em 2005. O modelo foi baseado na teoria dos Algoritmos Genéticos, sendo que, teve como variáveis indicadores ambientais, socioeconômicos, epidemiológicos e entomológicos. Os resultados obtidos possibilitaram observar as diferentes variáveis que influenciaram na incidência da Malária, considerando as especificações adotadas pelo model

INCREASED WATER STORAGE CAPACITY IN CACTUS WOOD: A STUDY IN THE TRIBE CEREEAE (CACTOIDEAE, CACTACEAE)

Secondary xylem of fibrous cactus wood is characterized by short narrow vessel elements with both simple perforation plates and large intervessel pits, libriform septate fibers, and large rays. These are present in basal cactus taxa, as well as in many other groups of the family. In Cactoideae, the most diversified and most derived subfamily, there are remarkable variations found in the secondary xylem, with the more highly derived taxa containing the greatest water storage capacity. Unlignified parenchyma is one specialization found in the fibrous wood of cacti. We observed this tissue in the secondary xylem at the base of the sterns of several Brazilian endemic species of Arrojadoa, Melocactus, and Stephanocereus, all members of the tribe Cereeae. In Arrojadoa and Melocactus the unlignified parenchyma occurs in lines and bands amongst the axial and radial xylem elements, while in Stephanocereus it is mainly restricted to the rays and does not form bands. We address the adaptive importance of the unlignified parenchyma in the fibrous wood in tribe Cereeae and the family Cactaceae as a whole.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)[98/15102-1]Conselho Nacional de Desenvolvimento Cientifico e Tecnologico-CNPqConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Anatomy of Brazilian Cereeae (subfamily Cactoideae, Cactaceae): Arrojadoa Britton & Rose, Stephanocereus A. Berger and Brasilicereus Backeberg

(Anatomy of Brazilian Cereeae (subfamily Cactoideae, Cactaceae): Arrojadoa Britton & Rose, Stephanocereus A. Berger wâBrasilicereus Backeberg). Arrojadoa, Stephanocereus and Brasilicereus are endemic Brazilian Cereeae, occurring along the Espinhaço Range, in the campos rupestres, cerrados and caatingas, from northern Minas Gerais to southern Bahia. The genera are columnar, erect to semi-erect cacti, except for one species, A bahiensis, which is globose. This study describes the anatomy of dermal, fundamental and vascular systems, aiming to find diagnostic characters for the genera and species. Basal portions of stems were sectioned transversely and longitudinally, and stained with Astrablue and Safranin. The species share a uniseriate epidermis, with thick cuticle; well developed collenchymatic hypodermis, containing prismatic crystals; cortex with numerous mucilage cells, druses and vascular bundles; outside cortex as a palisade parenchyma; periderm composed of lignified cork cells alternating with suberized cells; pheloderm consisting of a few layers of thin-walled cells; phloem composed of solitary or multiple of two to three sieve tube elements, companion cells, axial and radial parenchyma; secondary xylem with solitary to multiple vessels, with simple perforation plates and alternate bordered to semi-bordered pits; axial parenchyma scanty vasicentric to incomplete; libriform septate fibres; large rays. Unlignified parenchyma is seen in the secondary xylem, varying from a few cells to bands among axial and radial elements. The following are considered diagnostic characters: the shape of lignified phellem cells, cubic to radially elongate, which individualizes S. leucostele; an underdeveloped hypodermis and the occurrence of sclereids in the cortex are exclusive to Brasilicereus markgrqfii

Mechanical Innovations of a Climbing Cactus: Functional Insights for a New Generation of Growing Robots

International audienceClimbing plants are being increasingly viewed as models for bioinspired growing robots capable of spanning voids and attaching to diverse substrates. We explore the functional traits of the climbing cactus Selenicereus setaceus (Cactaceae) from the Atlantic forest of Brazil and discuss the potential of these traits for robotics applications. The plant is capable of growing through highly unstructured habitats and attaching to variable substrates including soil, leaf litter, tree surfaces, rocks, and fine branches of tree canopies in wind-blown conditions. Stems develop highly variable cross-sectional geometries at different stages of growth. They include cylindrical basal stems, triangular climbing stems and apical star-shaped stems searching for supports. Searcher stems develop relatively rigid properties for a given cross-sectional area and are capable of spanning voids of up to 1 m. Optimization of rigidity in searcher stems provide some potential design ideas for additive engineering technologies where climbing robotic artifacts must limit materials and mass for curbing bending moments and buckling while climbing and searching. A two-step attachment mechanism involves deployment of recurved, multi-angled spines that grapple on to wide ranging surfaces holding the stem in place for more solid attachment via root growth from the stem. The cactus is an instructive example of how light mass searchers with a winged profile and two step attachment strategies can facilitate traversing voids and making reliable attachment to a wide range of supports and surface

Failure without Tears: Two-Step Attachment in a Climbing Cactus

International audienceClimbing plants can be extremely adaptable to diverse habitats and capable of colonising perturbed, unstructured, and even moving environments. The timing of the attachment process, whether instantaneous (e.g., a pre-formed hook) or slow (growth process), crucially depends on the environmental context and the evolutionary history of the group concerned. We observed how spines and adhesive roots develop and tested their mechanical strength in the climbing cactus Selenicereus setaceus (Cactaceae) in its natural habitat. Spines are formed on the edges of the triangular cross-section of the climbing stem and originate in soft axillary buds (areoles). Roots are formed in the inner hard core of the stem (wood cylinder) and grow via tunnelling through soft tissue, emerging from the outer skin. We measured maximal spine strength and root strength via simple tensile tests using a field measuring Instron device. Spine and root strengths differ, and this has a biological significance for the support of the stem. Our measurements indicate that the measured mean strength of a single spine could theoretically support an average force of 2.8 N. This corresponds to an equivalent stem length of 2.62 m (mass of 285 g). The measured mean strength of root could theoretically support an average of 13.71 N. This corresponds to a stem length of 12.91 m (mass of 1398 g). We introduce the notion of two-step attachment in climbing plants. In this cactus, the first step deploys hooks that attach to a substrate; this process is instantaneous and is highly adapted for moving environments. The second step involves more solid root attachment to the substrate involving slower growth processes. We discuss how initial fast hook attachment can steady the plant on supports allowing for the slower root attachment. This is likely to be important in wind-prone and moving environmental conditions. We also explore how two-step anchoring mechanisms are of interest for technical applications, particularly for soft-bodied artefacts, which must safely deploy hard and stiff materials originating from a soft compliant body

Trellis-forming stems of a tropical liana Condylocarpon guianense (Apocynaceae): A plant-made safety net constructed by simple “start-stop” development

International audienceTropical vines and lianas have evolved mechanisms to avoid mechanical damage during their climbing life histories. We explore the mechanical properties and stem development of a tropical climber that develops trellises in tropical rain forest canopies. We measured the young stems of Condylocarpon guianensis (Apocynaceae) that construct complex trellises via self-supporting shoots, attached stems, and unattached pendulous stems. The results suggest that, in this species, there is a size (stem diameter) and developmental threshold at which plant shoots will make the developmental transition from stiff young shoots to later flexible stem properties. Shoots that do not find a support remain stiff, becoming pendulous and retaining numerous leaves. The formation of a second TYPE II (lianoid) wood is triggered by attachment, guaranteeing increased flexibility of light-structured shoots that transition from self-supporting searchers to interconnected net-like trellis components. The results suggest that this species shows a "hard-wired" development that limits self-supporting growth among the slender stems that make up a liana trellis. The strategy is linked to a stem-twining climbing mode and promotes a rapid transition to flexible trellis elements in cluttered densely branched tropical forest habitats. These are situations that are prone to mechanical perturbation via wind action, tree falls, and branch movements. The findings suggest that some twining lianas are mechanically fine-tuned to produce trellises in specific habitats. Trellis building is carried out by young shoots that can perform very different functions via subtle development changes to ensure a safe space occupation of the liana canopy