Abstract: Extractives that provide natural resistance to Bagassa guianensis Aubl. heartwood were examined. Soil-bed tests showed that the B. guianensis heartwood resistance was significantly reduced after ethyl acetate extraction, whereas methanol and especially water extractions improved the resistance. The ethyl acetate extract was submitted to a bioguided fractionation, and fractions were tested against one wood-destroying fungal strain (Pycnoporus sanguineus) and two human pathogenic fungal strains (Candida glabrata (yeast) and Trichophyton rubrum (filamentous dermatophyte)). Fraction F7, which exhibited the strongest antifungal activity, was subsequently fractionated by high performance liquid chromatography (HPLC). Six previously described compounds were isolated. Although the two moracins, 6-O-methyl-moracin N (3) and moracin N (4) were the most active against fungal strains with MIC values between 4 and 16 μg ml -1, the isolated compounds showed less or equivalent antifungal activity than the initial fraction. Possible synergism between compounds 3 and 4 and other secondary metabolites have been hypothesized. Our study demonstrated that this extract as a whole might be used as a wood preservation or antimycotic product. © 2012 Elsevier Ltd.

Abstract: Plant phenology characterises the seasonal cyclicity of biological events such as budburst, flowering, fructification, leaf senescence and leaf fall. These biological events are genetically pre-determined but also strongly modulated by climatic conditions, particularly temperature, daylength and water availability. Therefore, the timing of these events is considered as a good indicator of climate change impacts and as a key parameter for understanding and modelling vegetation-climate interactions. In situ observations, empirical or bioclimatic models and remotely sensed time-series data constitute the three possible ways for monitoring the timing of plant phenological events. Remote sensing has the advantage of being the only way of surface sampling at high temporal frequency and, in the case of satellite-based remote sensing, over large regions. Nevertheless, exogenous factors, particularly atmospheric conditions, lead to some uncertainties on the seasonal course of surface reflectance and cause bias in the identification of vegetation phenological events. Since 2005, a network of forest and herbaceous sites has been equipped with laboratory made NDVI sensors to monitor the temporal dynamics of canopy structure and phenology at an intra-daily time step. In this study, we present recent results obtained in several contrasting biomes in France, French Guiana, Belgium and Congo. These sites represent a gradient of vegetation ecosystems: the main evergreen and deciduous forest ecosystems in temperate climate region, an evergreen tropical rain forest in French Guiana, an herbaceous savanna ecosystem in Congo, and a succession of three annual crops in Belgium. In this paper, (1) we provide an accurate description of the seasonal dynamics of vegetation cover in these different ecosystems (2) we identify the most relevant remotely sensed markers from NDVI time-series for determining the dates of the main phenological events that characterize these ecosystems and (3) we discuss the relationships between temporal canopy dynamics and climate factors. In addition to its importance for phenological studies, this ground-based Network of NDVI measurement provides data needed for the calibration and direct validation of satellite observations and products. © 2012 Elsevier Inc.

Abstract: Volatile terpenes are among the most diverse class of defensive compounds in plants, and they are implicated in both direct and indirect defense against herbivores. In terpenes, both the quantity and the diversity of compounds appear to increase the efficiency of defense as a diverse blend of compounds provides a more efficient protection against a broader range of herbivores and limits the chances that an enemy evolves resistance. Theory predicts that plant defensive compounds should be allocated differentially among tissues according to the value of the tissue, its cost of construction and the herbivore pressure on it. We collected volatile terpenes from bark and leaves of 178 individual tree belonging to 55 angiosperm species in French Guiana and compare the kind, amount, and diversity of compounds in these tissues. We hypothesized that in woody plants, the outermost part of the trunk should hold a more diverse blend of volatile terpenes. Additionally, as herbivore communities associated with the leaves is different to the one associated with the bark, we also hypothesized that terpene blends should be distinct in the bark vs. the leaves of a given species. We found that the mixture of volatile terpenes released by bark is different and more diverse than that released by leaves, both in monoterpenes and sesquiterpenes. This supports our hypothesis and further suggests that the emission of terpenes by the bark should be more important for trunk defense than previously thought.

Abstract: A new naphthoquinone derivative was isolated from the heartwood of the teak stem. The chemical structure of this new compound, 4',5'-dihydroxy-epiisocatalponol, was determined using 1-D and 2-D nuclear magnetic resonance experiments, vibrational circular dichroism, HRMS, and optical rotation. We showed that this new naphthoquinone derivative plays a key role in the variability of decay resistance in teak wood. A high negative correlation was found between its concentration and the mass losses of the wood samples after exposure to the brown rot Antrodia sp., the fungus that is the most virulent against teak (R = -0.9; ρ < 0.0001). In-vitro bioassays allowed us to demonstrate that 4',5'-dihydroxy-epiisocatalponol acted as a fungicide against Trametes versicolor (white rot) at 58 mg ml -1 (0.22 mM). Overall, our results demonstrated that the concentration of 4',5'-dihydroxy-epiisocatalponol could be used as a new tool to evaluate teak wood durability. © 2012 Elsevier Ltd.

Abstract: 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. © 2012 Elsevier Ltd.