O. Huber

Bio: O. Huber is an academic researcher. The author has contributed to research in topics: Flora & Vegetation (pathology). The author has an hindex of 1, co-authored 1 publications receiving 24 citations.

Composition and cytotoxic activity of essential oils from Croton matourensis and Croton micans from Venezuela.

Abstract: The chemical composition and cytotoxic activity of the essential oils extracted from leaves of Croton matourensis and flowers and leaves of Croton micans were investigated. GC-FID and GC-MS analysis revealed that forty six compounds comprised 95.5 % of C. matourensis essential oil, with the main components being fenchyl acetate (19.5%), methyleugenol (14.2%), isoelemicine (11.3%), elemicine (7.6%), spathulenol (6.9%) and valencene (5.8%). In the analysis of C. micans oils, 63 compounds that comprised 98.9% were identified from the flower oil, the principal being fenchyl acetate (41.6%), α-caryophyllene (12.6%), β-cubebene (5.0%), βcaryophyllene (5.5%), α-cubebene (5.3%), β-elemene (4.7%) and valencene (4.6%). The oil from leaves gave fenchyl acetate (25.3%) α-caryophyllene (20.7%), α-selinene (12.8%) and β-bourbene (9.3%) as major constituents. The cytoxicity of these oils was screened by the MTT method against three human tumour cell lines and primary culture of human dermis fibroblasts (normal control cells). The results indicate that the oils have a moderate cytotoxicity against LoVo (colon carcinoma), X-17 (colon carcinoma), HeLa (cervical cancer), and control cells.

Inventory of related wild species of priority crops in Venezuela

Abstract: A prerequisite in any conservation programme of Plant Genetic Resources is estimation of diversity. The inventory of wild and naturalized relatives of priority crops in Venezuela (CWR) is based on the main Catalogues of Flora in the country, selecting taxa closely related to crops, according to the concepts of “gene pool” and “taxonomic group”. We included 47 genera, 217 species and 228 taxa belonging to 28 plant families. Among them, those with higher richness are: Fabaceae, Solanaceae, Araceae, Lauraceae, Dioscoreaceae, Poaceae, Rosaceae and Myrtaceae. Genera with a higher number of species are Xanthosoma, Persea, Dioscorea, Prunus, Psidium, Phaseolus, Solanum, Vigna, Capsicum, Manihot, Theobroma, Ipomoea and Oryza. A total of 26 endemic species are found, which belong to genera Xanthosoma, Persea, Dioscorea, Prunus and Manihot. The primary gene pool of crops include native species from genera such as Manihot, Solanum (Section Petota), Lycopersicon, Ananas, Capsicum, Dioscorea, Xanthosoma, Phaseolus, Theobroma, Ipomoea, Gossypium, Arracacia and Psidium. Genera with native species weakly related to crops are Saccharum, Persea, Ipomoea, Prunus, Vigna, Solanum (Section Melongena) and Daucus. Crop genera without native species in Venezuela are Allium, Musa, Brassica, Spinacia, Helianthus, Pisum, Lactuca, Citrus, Elaeis, Beta, Glycine and Triticum. Only a few taxa have already been evaluated according to the IUCN criteria, and Venezuelan accessions of crop wild relatives in national and international genebanks are very scarce.

Novelties in Selaginella (Selaginellaceae - Lycopodiophyta), with emphasis on Brazilian species.

Abstract: In this paper, I describe five new species of Selaginella from Brazil (Selaginella nanuzae, Selaginella neospringiana, Selaginella pellucidopunctata, Selaginella stomatoloma, and Selaginella trygonoides), compare them to morphologically similar species, and provide a preliminary conservation status assessment for each. The new species are illustrated with scanning electron photomicrographs of stem sections, leaves, and spores, when available. Also discussed in this paper are ten species, mainly from Brazil and with new distribution records, and the forthcoming resurrection of three species also occurring in Brazil. Three further non-native and presumed naturalized species are recognized in Brazil, and publication of one additional taxon is planned. Eighty-six Selaginella species are now known from Brazil and, of these, 80 are native (including 26 / 32.5%, endemic), and six are introduced. Brazil and Mexico have the second highest number of native Selaginella species in the Neotropics after Venezuela, which is estimated to have about 100. Of the newly documented species, Selaginella cabrerensis is now known to occur in French Guiana, Brazil, and Bolivia, in addition to Colombia, and Selaginella arroyoana and Selaginella chiquitana are synonymized under it. Likewise, Selaginella potaroensis is also recorded from Costa Rica and Brazil, and Selaginella seemannii from Panama and Brazil. Finally, leaf marginal stomata are reported on the newly described species and their functionality is discussed under Selaginella stomatoloma.

Spatial relations and population structure of a dominant tree along a treeline ecotone in the Tropical Andes: interactions at gradient and plant-neighbourhood scales

Abstract: Background: Studies in temperate mountains suggest that plant–plant interactions modulate tree establishment above the forest line. In tropical mountains worldwide this issue remains largely unexplored. Aims: To analyse the population structure and local spatial relationships of a dominant tree at a species-rich tropical Andean forest line. Methods: We determined changes in the population structure of Diplostephium venezuelense along an elevation gradient between continuous forest and open paramo and analysed plant community structure and superficial rock cover in the neighbourhood of saplings and adults at the upper forest line. Results: Sapling and adult densities were highest in low-altitude paramos adjacent to the forest line and at the borders of small forest islands. Saplings showed local spatial aggregation, were positively associated with small boulders and low shrubs, and negatively associated with mosses and lichens. However, no spatial association was found between scattered adults in the param...