Sextonia Rubra Research Articles

Low-frequency somatic mutations are heritable in tropical trees Dicorynia guianensis and Sextonia rubra

Somatic mutations potentially play a role in plant evolution, but common expectations pertaining to plant somatic mutations remain insufficiently tested. Unlike in most animals, the plant germline is assumed to be set aside late in development, leading to the expectation that plants accumulate somatic mutations along growth. Therefore, several predictions were made on the fate of somatic mutations: mutations have generally low frequency in plant tissues; mutations at high frequency have a higher chance of intergenerational transmission; branching topology of the tree dictates mutation distribution; and exposure to UV (ultraviolet) radiation increases mutagenesis. To provide insights into mutation accumulation and transmission in plants, we produced two high-quality reference genomes and a unique dataset of 60 high-coverage whole-genome sequences of two tropical tree species, Dicorynia guianensis (Fabaceae) and Sextonia rubra (Lauraceae). We identified 15,066 de novo somatic mutations in D. guianensis and 3,208 in S. rubra, surprisingly almost all found at low frequency. We demonstrate that 1) low-frequency mutations can be transmitted to the next generation; 2) mutation phylogenies deviate from the branching topology of the tree; and 3) mutation rates and mutation spectra are not demonstrably affected by differences in UV exposure. Altogether, our results suggest far more complex links between plant growth, aging, UV exposure, and mutation rates than commonly thought.

Composition of antifungal volatile organic compounds in Sextonia rubra fruit by molecular networks

Composition of antifungal volatile organic compounds in Sextonia rubra fruit by molecular networks

Sextonia rubra (Mez.) van der Werff sawmills residues as a valuable resource for the production of larvicidal extracts against Ae. aegypti Linnaeus (Diptera: Culicidae)

Sextonia rubra (Mez.) van der Werff sawmills residues as a valuable resource for the production of larvicidal extracts against Ae. aegypti Linnaeus (Diptera: Culicidae)

Towards the optimization of botanical insecticides research: Aedes aegypti larvicidal natural products in French Guiana

Natural products have proven to be an immeasurable source of bioactive compounds. The exceptional biodiversity encountered in Amazonia, alongside a rich entomofauna and frequent interactions with various herbivores is the crucible of a promising chemodiversity. This prompted us to search for novel botanical insecticides in French Guiana. As this French overseas department faces severe issues linked to insects, notably the strong incidence of vector-borne infectious diseases, we decided to focus our research on products able to control the mosquito Aedes aegypti. We tested 452 extracts obtained from 85 species originating from 36 botanical families and collected in contrasted environments against an Ae. aegypti laboratory strain susceptible to all insecticides, and a natural population resistant to both pyrethroid and organophosphate insecticides collected in Cayenne for the most active of them. Eight species (Maytenus oblongata Reissek, Celastraceae; Costus erythrothyrsus Loes., Costaceae; Humiria balsamifera Aubl., Humiriaceae; Sextonia rubra (Mez) van der Werff, Lauraceae; Piper hispidum Sw., Piperaceae; Laetia procera (Poepp.) Eichl., Salicaceae; Matayba arborescens (Aubl.) Radlk., Sapindaceae; and Cupania scrobitulata Rich., Sapindaceae) led to extracts exhibiting more than 50% larval mortality after 48 h of exposition at 100 µg/mL against the natural population and were considered active. Selectivity and phytochemistry of these extracts were therefore investigated and discussed, and some active compounds highlighted. Multivariate analysis highlighted that solvents, plant tissues, plant family and location had a significant effect on mortality while light, available resources and vegetation type did not. Through this case study we highlighted that plant defensive chemistry mechanisms are crucial while searching for novel insecticidal products.

Biosynthetic investigation of \u03b3-lactones in Sextonia rubra wood using in situ TOF-SIMS MS/MS imaging to localize and characterize biosynthetic intermediates

Molecular analysis by parallel tandem mass spectrometry (MS/MS) imaging contributes to the in situ characterization of biosynthetic intermediates which is crucial for deciphering the metabolic pathways in living organisms. We report the first use of TOF-SIMS MS/MS imaging for the cellular localization and characterization of biosynthetic intermediates of bioactive γ-lactones rubrynolide and rubrenolide in the Amazonian tree Sextonia rubra (Lauraceae). Five γ-lactones, including previously reported rubrynolide and rubrenolide, were isolated using a conventional approach and their structural characterization and localization at a lateral resolution of ~400 nm was later achieved using TOF-SIMS MS/MS imaging analysis. 2D/3D MS imaging at subcellular level reveals that putative biosynthetic γ-lactones intermediates are localized in the same cell types (ray parenchyma cells and oil cells) as rubrynolide and rubrenolide. Consequently, a revised metabolic pathway of rubrynolide was proposed, which involves the reaction between 2-hydroxysuccinic acid and 3-oxotetradecanoic acid, contrary to previous studies suggesting a single polyketide precursor. Our results provide insights into plant metabolite production in wood tissues and, overall, demonstrate that combining high spatial resolution TOF-SIMS imaging and MS/MS structural characterization offers new opportunities for studying molecular and cellular biochemistry in plants.

Madeiras históricas em embarcações tradicionais do baixo rio São Francisco

Embarcações tradicionais estão diretamente ligadas à história do rio São Francisco e de suas comunidades ribeirinhas, sendo este um dos maiores rios navegáveis que permitiram a colonização da região Nordeste do Brasil. Este estudo objetivou conhecer as madeiras utilizadas na construção de embarcações do baixo rio São Francisco, gerando subsídios para melhor compreender as relações de uso de recursos florestais destinados à carpintaria naval tradicional. Foram estudadas quatro embarcações pertencentes ao acervo do Museu Nacional do Mar, São Francisco do Sul, Santa Catarina. A coleta das madeiras históricas foi realizada com auxílio de trado de incremento para posterior produção de lâminas histológicas e descrição anatômica. A identificação das madeiras foi realizada por comparação com coleção de referência. Foram identificadas onze espécies de madeiras usadas de forma mista na construção dos componentes das embarcações. São elas: Apuleia leiocarpa (Fabaceae), Astronium graveolens (Anacardiaceae), Brosimum gaudichaudii (Moraceae), Dalbergia nigra (Fabaceae), Hymenaea courbaril (Fabaceae), Manilkara dardanoi (Sapotaceae), Myracrodruon urundeuva (Anacardiaceae), Paubrasilia echinata (Fabaceae), Sextonia rubra (Lauraceae), Tabebuia aurea (Bignoniaceae) e Terminalia glabrencens (Combretaceae). O conhecimento sobre as madeiras e seu emprego tecnológico imprimem à construção de embarcações tradicionais um rico significado cultural que integra pessoas e árvores na paisagem do rio São Francisco.

Theoretical and experimental deflections of glued laminated timber beams made from a tropical hardwood

Nondestructive testing (NDT) can play an important role in improving the quality and reliability of tropical hardwood as an engineering material. By means of these methods, the stiffness of the material can be determined and the information used to improve its structural performance. Although, it is a usual approach for qualifying the material used to manufacture engineered wood products made mainly from softwoods, it is not so common for tropical hardwoods. Additionally, the lack of information regarding properties of glulam beam made from these kinds of wood is evident. In this context, the paper aimed at evaluating the theoretical and experimental deflection of glulam beams made from the Brazilian hardwood louro-vermelho (Sextonia rubra). Initially, the stiffness of each lamina was determined nondestructively using transverse vibration method (E dtv), which has been demonstrated to be the most suitable method for this wood species. Then, ten 5-lamina glulam beams were assembled according to descending lamina E dtv values. The experimental evaluation was performed using a four-point bending schedule. In general, the theoretical values of deflection were 2% higher than the experimental ones. The transverse vibration showed to be a suitable method to both measure lamina stiffness and predict glulam beam deflection.

Essential oils of the Sextonia rubra (Mez ) van der Werff (Lauraceae)

The essential oils of the leaves and branches of Sextonia rubra were obtained by hydrodistillation and analyzed by GC-FID and GC-MS. In the leaves were identified as the major constituents α-pinene (21.7%), β-pinene (15.4%), α-copaene (12.5%) and germacrene D (12.1%). In the branches essential oil, α-copaene (22.9%), β-selinene (7.9%) and β-elemene (7.2%) were identified as the most abundant constituents. This paper describes for the first time the composition of these essential oils.

The wood preservative potential of long-lasting Amazonian wood extracts

Investigations were carried out on the efficacy of extracts from seven Amazonian woods (Bagassa guianensis, Manilkara huberi, Sextonia rubra, Vouacapoua americana, Andira surinamensis, Handroanthus serratifolius, and Qualea rosea) with varying natural durability to reduce soft-rot degradation in a 6-wk soil-bed test. Six of the wood extracts had shown efficacy against soft-rot fungi. In particular, the preservation efficacies of B. guianensis, H. serratifolius, and S. rubra extracts were highly significant up to retention levels of 23, 25, and 12 kg m−3, respectively. Three extracts (A. surinamensis, H. serratifolius, and Q. rosea) were then tested against Gloeophyllum trabeum (brown rot) and Trametes versicolor (white rot), in an agar-block test. H. serratifolius wood extract was very efficient at protecting P. sylvestris samples at 5.1 kg m−3 against the brown rot. This extract could be used as a basis for new wood protectant formulations.

Nondestructive Evaluation of a Tropical Hardwood: Interrelationship Between Methods and Physical-Acoustical Variables

The paper aimed at evaluating the interrelationship between three nondestructive methods to predict the stiffness of a tropical hardwood (Sextonia rubra). Lumber material from Sextonia rubra was collected, ripped and planned and boards were then nondestructively tested using three methods: stress wave, transverse vibration and static bending. Stress wave (Edsw) and transverse vibration (Edtv) testing were done using commercial equipment while the static bending testing (Esb) was conducted according to the ASTM D4761. According to the results, linear regression models could be fitted to explain the interrelationship between the nondestructive properties. The best model was observed for the relationship between Esb and Edtv (R 2 =0.946), followed by Esb/Edsw (R 2 =0.834) and Edtv/Edsw (R 2 =0.817). The values of dynamic modulus of elasticity were frequently higher (Edsw=4.19 %; Edtv= 9.44 %) than the Esb values (15314 N/mm 2 ). On the other hand, Edtv values were higher (5.35%) than Edsw values. It can be concluded that the three nondestructive testing methods studied are suitable to estimate the stiffness of this tropical hardwood. However, corrected models must be employed to improve the reliability of the predicted values.

The termiticidal activity of Sextonia rubra (Mez) van der Werff (Lauraceae) extract and its active constituent rubrynolide

Termites are degradation agents that inflict severe damage on wood. Some long-lasting Amazonian trees can resist these insects by producing toxic secondary metabolites. These metabolites could potentially replace synthetic termiticidal products which are becoming more restricted to use. Sextonia rubra is resistant to termite-induced degradation. It has been demonstrated that this species naturally produces an ethyl-acetate-soluble termiticidal metabolite, rubrynolide, to protect its wood. Assays in the presence of tropical and invasive termites established that both rubrynolide and crude ethyl acetate extract from S. rubra wood can be used as a treatment for the protection of sensitive woods against termites. Rubrynolide and S. rubra extract are promising candidates for the replacement of synthetic termiticides.

Effect of nondestructive testing of laminations on the bending properties of glulam beams made from louro-vermelho (Sextonia rubra)

This work aims to assess the bending properties of glued laminated timber beams (glulam) manufactured with species louro-vermelho (Sextonia rubra). Laminations were nondestructively tested using the transverse vibration method (E Mlam). Then 10 glulam beams were manufactured and tested in static bending according to ASTM D 198 standard, having modulus of elasticity (E M), modulus of rupture (fM), and bending moment (M) determined. The finished beams were also tested by the transverse vibration method (E Mvt). It was noted that the E Mvt value was only 2% lower than the E M value. Using laminations with a high modulus of elasticity did allow effective gain in stiffness. Therefore, results indicate that the transverse vibration method is a valid, reliable technique both for testing glulam laminations and for assessing stiffness in finished beams. Bending properties in glulam beams were influenced by the stiffness of constituent laminations.

Genetic variation for growth, morphological, and physiological traits in a wild population of the Neotropical shade­tolerant rainforest tree Sextonia rubra (Mez) van der Werff (Lauraceae)

Quantitative genetic diversity is a fundamental component of the interaction between natural populations and their environment. In breeding programmes, quantitative genetic studies on tropical trees have so far focused on fast-growing, light-demanding species, but no information exists on shade-tolerant, slow-growing species. For this study, 27 3-year-old open-pollinated families of the Neotropical shade-tolerant rainforest tree Sextonia rubra were measured in semicontrolled conditions for 20 morphological, growth, and photosynthesis traits; the effect of genetic relatedness, habitat of provenance, and mother tree status on seedling traits was analysed. Nine traits displayed significant genetic effects, while mother tree status and habitat effects were not significant (P > 0.05) for an y trait. Estimated heritability varied between 0.14 and 0.28, with growth-related traits having the highest values. Additive genetic variation correlated positively with nonheritable variation, suggesting that ecological–evolutionary factors increasing or decreasing additive genetic variance may also affect nonheritable variation in the same direction. Our results suggest that quantitative genetic variability should be taken into account in ecological studies on, and in the management of, natural tropical rainforests; further research is needed to investigate genetic × environment interactions, in particular from the point of view of the genetic response of shade-tolerant plant species to variations in light availability.

Decay susceptibility of Amazon wood species from Brazil against white rot and brown rot decay fungi 10th EWLP, Stockholm, Sweden, August 25–28, 2008

Abstract A total of 28 tropical Amazon woods – many of them rarely used – from Tapajós National Forest, Pará state, Brazil, were tested for their natural resistance against the decay fungi: Ganoderma applanatum, Trametes versicolor, Pycnoporus sanguineus, Meruliporia incrassata, and Gloeophyllum trabeum. The wood resistance classification was made according to the ASTM D 2017-81 method. High variability on susceptibility to wood decay fungi was found. Their mean weight losses varied from 0.6% to 45.6%. Highly resistant species include: Astronium gracile, Bagassa guianensis, Caryocar villosum, Claricia racemosa, Diplotropis purpurea, Dipteryx odorata, Hymenaea courbaril, Manilkara huberi, Mezilaurus itauba, Sextonia rubra, Tabebuia incana, and Vatairea paraensis. The following wood species are less durable: Brosimum parinarioides, Jacaranda copaia, Laetia procera, Pouteria pachycarpa, Virola caducifolia, and Trattinnickia rhoifolia. Meruliporia incrassata caused extensive weight losses in most of the investigated Amazon wood species.

Low Inbreeding and High Pollen Dispersal Distances in Populations of Two Amazonian Forest Tree Species

ABSTRACTRecent studies suggest that tropical tree species exhibit low inbreeding and high gene dispersal levels despite the typically low density of conspecifics in tropical forests. To examine this, we undertook a study of pollen gene dispersal and mating system of two Amazonian tree species. We analyzed 341 seeds from 33 trees at four microsatellite loci in a Carapa guianensis population from Brazil, and 212 seeds from 22 trees at four microsatellite loci in a Sextonia rubra population from French Guiana. Differentiation of allele frequencies among the pollen pool of individual trees was ΦFT= 0.053 (95% CI: 0.027–0.074) for C. guianensis and ΦFT= 0.064 (95% CI: 0.017–0.088) for S. rubra. The mean pollen dispersal distances were estimated at 69–355 m for C. guianensis, and 86–303 m for S. rubra, depending on the pollen dispersal model and the estimate of reproductive tree density used. The multi‐locus outcrossing rate was estimated at 0.918 and 0.945, and the correlation of paternity at 0.089 and 0.096, for C. guianensis and S. rubra, respectively, while no significant levels of biparental inbreeding were detected. Comparing trees with high and low local density of conspecifics, we found no evidence for differences in inbreeding levels. The results are discussed within the framework of the emerging picture of the reproductive biology of tropical forest trees.

Impact of selective logging on genetic composition and demographic structure of four tropical tree species

Over-exploitation and fragmentation are serious problems for tropical forests. Most sustainable forest management practices avoid clear-cuts and apply selective logging systems focused on a few commercial species. We applied a simulation model to estimate the impact of such selective logging scenarios on the genetic diversity and demography of four tropical tree species from French Guiana. The simulations used data on genetic and demographic composition, growth, phenology and pollen and seed dispersal obtained for Dicorynia guianensis, Sextonia rubra, Symphonia globulifera and Vouacapoua americana at the experimental site in Paracou. Whereas Symphonia globulifera serves as a model for a species with low logging pressure, the other three species represent the most exploited tree species in French Guiana. In simulations with moderate logging, typical for French Guiana, with large cutting diameter (>60 cm diameter) and long cutting cycles (65 years), the two species V. americana and Sextonia rubra were not able to recover their initial stock at the end of the rotation period, with a large decrease in the number of individuals and in basal area. Under a more intensive logging system (cutting diameter >45 cm diameter, cutting cycles of 30 years) that is common practice in the Brazilian Amazon, only Symphonia globulifera showed no negative impact. Generally, the differences between the genetic parameters in the control scenarios without logging and the logging scenarios were surprisingly small. The main reasons for this were the overlapping of generations and the effective dispersal ability of gene vectors in all species, which guarantee relative homogeneity of the genetic structure in different age classes. Nevertheless, decreasing the population size by logging reduced the number of genotypes and caused higher genetic distances between the original population and the population at the end of the logging cycles. Sensitivity analysis showed that genetic changes in the logging scenarios were principally determined by the growth, densities and cutting diameter of each species, and only to a very small extent by the reproductive system including factors such as pollen and seed dispersal and flowering phenology.

Gene flow and mating system of the tropical tree Sextonia rubra

AbstractIn this paper we report a study of the mating system and gene flow of Sextonia rubra, a hermaphroditic, insect pollinated tropical tree species with a geographic distribution in the Guyana Plateau and the Amazon. Using five microsatellites we analysed 428 seeds of 27 open pollinated families at the experimental site “Paracou” in French Guiana. We observed, compared to other tropical tree species, a high level of genetic diversity. We estimated parameters of the mating system and gene flow by using the mixed mating model and the TwoGener approach. The estimated multilocus outcrossing rate, tm, was 0.992 indicating nearly complete outcrossing. A significant level of biparental inbreeding and a small proportion of full-sibs were estimated for the 27 seed arrays. The differentiation of allelic frequencies among the pollen pools was ΦFT= 0.061. We estimated mean pollen dispersal distances between 65 m and 89 m according to the dispersal models used. The joint estimation of pollen dispersal and density of reproductive trees gave an effective density estimate of 2.1-2.2 trees/ha.

Sextonia, a New Genus of Lauraceae from South America

The genus Sextonia is described; it consists of two species, the rather widespread S. rubra and the new species S. pubescens, restricted to eastern Peru. Ocotea is the largest genus of neotropical Lauraceae, including at least 300 species (van der Werff, 1991). It is not surprising that with such a large number of species the genus shows considerable morphological variation, is difficult to delimit, and is in much need of a modern revision. Oftentimes the genus has been used to accommodate species that could not be adequately placed in other, better defined genera. As information from other disciplines, most notably wood and bark anatomy (Richter, 1981), has become available, some of the anomalous species have been removed from Ocotea and recognized as distinct genera. Rohwer et al. (1991) created the genus Chlorocardium for two species previously placed in Ocotea and discussed some other problematical species. I propose to recognize one of those species, until now treated as Ocotea rubra, as belonging to a distinct genus and will describe a new species of this genus as well. Sextonia van der Werff, gen. nov. TYPE: Sextonia rubra (Mez) van der Werff. Figure 1. Arbores magnae. Folia ad apices ramulorum aggregata. Inflorescentiae axillares, racemosae vel paniculatae. Tepala 6, inaequalia, 3 exteriora quam 3 interiora minora, erecta; stamina 9, 4-locellata, 6 exteriora locellis in arcu non profundo dispositis, 3 interiora locellis in 2 paribus superpositis; staminodia 3; receptaculum profundum. Fructus cupula insidens, ab ea 13 vel fere omnino obtecta. Large trees, to 45 m tall. Twigs thick, corky, terete. Leaves alternate, clustered near the tips of the branches, pinnately veined, without domatia. Inflorescences axillary, racemose or paniculate, ultimate divisions of inflorescences frequently not strictly cymose, but racemose. Tepals erect, unequal, the outer three smaller than the inner three; stamens 9, 4-celled, the outer 6 with the cells in a shallow arc, the inner 3 with the cells placed in two pairs, the filaments short, as wide as the anthers, staminodia 3; receptacle deep. Fruit initially enclosed in the cupule, at maturity either 2/ exserted or almost completely enclosed in the cupule. The new genus Sextonia is readily recognized by having clustered leaves and flowers with unequal tepals, characters already mentioned by Rohwer et al. (1991). The differences in wood and bark anatomy between Ocotea and Sextonia (as O. rubra) were amply discussed by Richter (1981), and indeed the main reason that Rohwer et al. (1991) did not describe a new genus to accommodate O. rubra was their reluctance to describe another monotypic genus. In a genus as large as Ocotea it is not surprising to find individual species or groups of species that differ in one or more morphological characters from the rest of the species, and finding such differences is not a sufficiently strong argument for describing a new genus. However, when such morphological differences are supported by differences in wood and bark anatomy the argument for a new genus is stronger. Three reasons made me consider the generic status of 0. rubra again. The first is the recent discovery of an undescribed species closely related to O. rubra, sharing with it the clustered leaves and flowers with unequal tepals, but differing in having pubescent flowers and racemose inflorescences. This new species has wood and bark anatomy similar to O. rubra. Describing this species in Ocotea would clearly be incorrect. The second argument is that during a study of the embryology of Lauraceae (Heo et al., in prep.) Ocotea rubra was found to differ clearly from the other four investigated species of Ocotea in having the mature embryo sac protruding from the nucellus, a character state otherwise only found in Beilschmiedia, Caryodaphnopsis, Cryptocarya, Endiandra, and Potameia, but lacking in genera considered closely related to Ocotea, such as Aiouea, Aniba, Cinnamomum, Licaria, Mezilaurus, and Nectandra. The third is that the inflorescences of the two species of Sextonia are different from those found in Ocotea. In Ocotea the flowers are arranged in cymes, with the lateral flowers of a cyme strictly opposite. In Sextonia rubra, however, the flowers are not arranged in cymes. Frequently the ultimate branching of the inflorescences appears racemose and flowers are not strictly opposite. The inflorescence types of Lauraceae and their importance for the suprageneric classification are discussed in detail by van NovoN 7: 436-439. 1997. This content downloaded from 157.55.39.151 on Thu, 07 Jul 2016 05:31:01 UTC All use subject to http://about.jstor.org/terms Volume 7, Number 4 van der Werff 437 1997 New Genus of Lauraceae