Wetlands are the largest global source of atmospheric methane (CH), a potent greenhouse gas. However, methane emission inventories from the Amazon floodplain, the largest natural geographic source of CH in the tropics, consistently underestimate the atmospheric burden of CH determined via remote sensing and inversion modelling, pointing to a major gap in our understanding of the contribution of these ecosystems to CH emissions. Here we report CH fluxes from the stems of 2,357 individual Amazonian floodplain trees from 13 locations across the central Amazon basin. We find that escape of soil gas through wetland trees is the dominant source of regional CH emissions. Methane fluxes from Amazon tree stems were up to 200 times larger than emissions reported for temperate wet forests and tropical peat swamp forests, representing the largest non-ebullitive wetland fluxes observed. Emissions from trees had an average stable carbon isotope value (δC) of -66.2 ± 6.4 per mil, consistent with a soil biogenic origin. We estimate that floodplain trees emit 15.1 ± 1.8 to 21.2 ± 2.5 teragrams of CH a year, in addition to the 20.5 ± 5.3 teragrams a year emitted regionally from other sources. Furthermore, we provide a 'top-down' regional estimate of CH emissions of 42.7 ± 5.6 teragrams of CH a year for the Amazon basin, based on regular vertical lower-troposphere CH profiles covering the period 2010-2013. We find close agreement between our 'top-down' and combined 'bottom-up' estimates, indicating that large CH emissions from trees adapted to permanent or seasonal inundation can account for the emission source that is required to close the Amazon CH budget. Our findings demonstrate the importance of tree stem surfaces in mediating approximately half of all wetland CH emissions in the Amazon floodplain, a region that represents up to one-third of the global wetland CH source when trees are combined with other emission sources.

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Recebido em 7/8/11; aceito em 11/1/12; publicado na web em 15/5/12 This work describes the phytochemical study of the methanol extract obtained from leaves of Guarea macrophylla, leading to the isolation and identification of three flavonoid glycosides (quercetin 3-O-b-D-glucopyranoside, quercetin 3-O-b-D-galactopyranoside, kaempferol 7-O-b-D-glucopyranoside) and a neolignan glucoside, dehydrodiconiferyl alcohol-4-b-D-glucoside. All compounds were identified by a combination of spectroscopic methods ( 1 H, 1D, 2D NMR, 13 C and UV), ESI-MS and comparison with the literature data. This is the first report of flavonoids in the genus Guarea and of a neolignan glucoside in the Meliaceae family.

Arctium lappa L. (Asteraceae) is used in folk medicine around the World, and shows several kinds of biological activity, particularly in vitro antitumor activity in different cell lines. This study evaluated the antiproliferative activity of the crude extract, semipurified fractions, and isolated compounds from the leaves of A. lappa, through bioassay-guided testing in Caco-2 cells. The crude extract was obtained with a 50% hydroethanolic extract and then partitioned with hexane, ethyl acetate, and n-butanol. The ethyl-acetate fraction (EAF) showed antiproliferative activity. This fraction was subjected to sequential column chromatography over silica gel to afford onopordopicrin (1), mixtures of 1 with dehydromelitensin-8-(4'-hydroxymethacrylate) (2), a mixture of 2 with dehydromelitensin (3), mixture of 1 with melitensin (4), dehydrovomifoliol (5), and loliolide (6). The compounds were identified by spectroscopic methods (NMR, MS) and comparison with literature data. This is the first description of compounds 2–5 from this species. The compounds tested in Caco-2 cells showed the following CC50 (µg/mL) values: 1: 19.7 ± 3.4, 1 with 2: 24.6 ± 1.5, 2 with 3: 27 ± 11.7, 1 with 4: 42 ± 13.1, 6 30 ± 6.2; compound 5 showed no activity.

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Philodendron is the second most diverse genus of the Araceae, a tropical monocot family with significant morphological diversity along its wide geographic distribution in the Neotropics. Although evolutionary studies of Philodendron were conducted in recent years, the phylogenetic relationship among its species remains unclear. Additionally, analyses conducted to date suggested the inclusion of all American representatives of a closely-related genus, Homalomena, within the Philodendron clade. A thorough evaluation of the phylogeny and timescale of these lineages is thus necessary to elucidate the tempo and mode of evolution of this large Neotropical genus and to unveil the biogeographic history of Philodendron evolution along the Amazonian and Atlantic rainforests as well as open dry forests of South America. To this end, we have estimated the molecular phylogeny for 68 Philodendron species, which consists of the largest sampling assembled to date aiming the study of the evolutionary affinities. We have also performed ancestral reconstruction of species distribution along biomes. Finally, we contrasted these results with the inferred timescale of Philodendron and Homalomena lineage diversification. Our estimates indicate that American Homalomena is the sister clade to Philodendron. The early diversification of Philodendron took place in the Amazon forest from Early to Middle Miocene, followed by colonization of the Atlantic forest and the savanna-like landscapes, respectively. Based on the age of the last common ancestor of Philodendron, the species of this genus diversified by rapid radiations, leading to its wide extant distribution in the Neotropical region.

BackgroundPhilodendron is the second largest genus of Araceae, being highly diverse in the Atlantic Forest biome, with nearly one third of the Brazilian species occurring in Southern Brazil, particularly in Rio de Janeiro state. During a local inventory in Silva Jardim municipality, we found a peculiar population of Philodendron growing in lowland rainforest.ResultsAfter morphological analysis and comparisons with similar species, the population proved to be a new undescribed species of subgenus Philodendron section Macrobelium.ConclusionsThe new species, named Philodendron luisae, is here described, illustrated and compared to morphologically close species.Electronic supplementary materialThe online version of this article (doi:10.1186/s40529-015-0082-x) contains supplementary material, which is available to authorized users.