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961.
Santos SC Costa WF Ribeiro JP Guimarães DO Ferri PH Ferreira HD Seraphin JC 《Fitoterapia》2002,73(4):292-299
A comparative study of tannin composition of three species known as barbatim?o (Stryphnodendron adstringens, Stryphnodendron polyphyllum and Dimorphandra mollis) was developed by TLC, hydrolysis followed by PC, and colorimetry. Principal component analysis of the data obtained showed strong differentiation between the genus Dimorphandra and Stryphnodendron. Additionally, barks from the two Stryphnodendron sp. also presented considerable differences in the tannin structure. 相似文献
962.
The antioxidant activity of the methanol extract of Hypericum triquetrifolium Turra (Hypericaceae) aerial part and of flavonoids isolated therein, I3,II8-biapigenin, quercetin-3-O-galactoside, kaempferol-3-O-glycoside, (-)-epicatechin and hypericin, was evaluated. The IC(50) resulted between 0.062 and 1 mg/ml. 相似文献
963.
Bacelar EA Correia CM Moutinho-Pereira JM Gonçalves BC Lopes JI Torres-Pereira JM 《Tree physiology》2004,24(2):233-239
Leaf-level morphological and structural adaptations to reduce water loss were examined in five olive (Olea europaea L.) tree cultivars (Arbequina, Blanqueta, Cobran?osa, Manzanilla and Negrinha) growing under field conditions with low water availability. Leaf measurements included leaf tissue thickness, stomatal density, leaf area, leaf mass per unit area, density of leaf tissue, relative water content, succulence, water saturation deficit, water content at saturation and cuticular transpiration rate. We found considerable genotypic differences among the cultivars. Negrinha, Manzanilla and Cobran?osa had more morphological and structural leaf adaptations to protect against water loss than the other cultivars. Manzanilla and Negrinha enhanced their sclerophylly by building parenchyma tissues and increasing protective structures like the upper cuticle and both the upper and lower epidermis. Cobran?osa exhibited good protection against water loss through high density of foliar tissue and by thick cuticle and trichome layers. Compared with the Negrinha, Manzanilla and Cobran?osa cultivars, Arbequina leaves had a thinner trichome layer, implying that the leaves were less protected against water loss; however, the development of smaller leaves may reduce water loss at the whole-plant level. Among cultivars, Blanqueta had the largest leaves and some anatomical traits that may lead to high water loss, especially from the adaxial surface. The mechanisms employed by the cultivars to cope with summer stress are discussed at the morpho-structural level. 相似文献
964.
Tostão Z Noronha JP Cabrita EJ Medeiros J Justino J Bermejo J Rauter AP 《Fitoterapia》2005,76(2):173-180
A novel oleanene triterpenetetrol was isolated from the chloroform extract of the aerial parts of Leontodon filii. Its structure was shown to be 2beta,3beta,15alpha,21beta-olean-12-ene-2,3,15,21-tetrol by chemical and spectroscopic methods. The fungicidal efficacy of the chloroform and methanol extracts of the plant was also evaluated, a protective effect being found against Plasmopara viticola, Botrytis cinerea, particularly powerful against Pyricularia oryzae. 相似文献
965.
Bruno Esteves António Velez Marques Idalina Domingos Helena Pereira 《Wood Science and Technology》2007,41(3):193-207
Heat treatment of Pinus pinaster and Eucalyptus globulus woods, two important species in Portugal, was performed in the absence of air by steaming, inside an autoclave, for 2–12 h
at 190–210°C. Mass losses increased with treatment time and temperature reaching 7.3% for pine and 14.5% for eucalypt wood.
The wood behaviour with moisture was improved. The equilibrium moisture content decreased by 46% for pine and 61% for eucalypt,
the dimensional stability increased (maximum anti-shrinking efficiency in the radial direction of 57 and 90% for pine and
eucalypt, respectively) and the surface wettability was lowered. In relation to mechanical properties, the modulus of elasticity
was little affected (maximum decrease of 5% for pine and 15% for eucalypt) but the bending strength was reduced (by 40% at
8% mass loss for pine and 50% at 9% mass loss for eucalypt wood). The variation of properties was related to treatment intensity
and mass loss but significant improvements could already be obtained for a 3–4% mass loss without impairing the mechanical
resistance. The response of eucalypt was higher than that of pinewood. Heat treatment of eucalypt wood shows an interesting
potential to improve the wood quality for solid timber products. 相似文献
966.
Felipe García-Oliva Juan F. Gallardo Lancho Noé Manuel Montaño Pilar Islas 《Agroforestry Systems》2006,66(2):93-100
Gains and losses of soil carbon (C), have been reported when tropical forests are converted to pastures. Regional studies
are crucial for setting regional baselines and explaining each particular trend, in order to solve this controversy. Tropical
deciduous forest (TDF) is under high deforestation pressure, mainly for conversion to pastures. The present study compared
soil organic C (SOC) and nitrogen (SON) in the surface layer (0–5 cm) of forest and pasture soils in a TDF of western Mexico.
SOC and SON concentrations were 18 and 60% lower in pasture soils than in forest soils, and C:N ratio increased in pasture
soils. Furthermore, pasture soils had lower labile C and available inorganic nitrogen (N) than forest soils. These results
can be explained as a reduction in C inputs to pasture soils and management-induced disruption of soil aggregates. In forest
soils, macroaggregates (> 250 μm) were predominant (85%), whereas in pasture soils they were reduced to 35% of dry sand-free soil mass. The estimated SOC
and SON losses from the top 5 cm of soil were 3 Mg C ha−1 and 0.9 Mg N ha−1, respectively. 相似文献
967.
Alfredo Manuel Bermúdez José María Fernández-Palacios Juana María González-Mancebo Jairo Patiño José Ramón Arévalo Rüdiger Otto Juan Domingo Delgado 《Annals of Forest Science》2007,64(1):109-119
We analyzed a post-clearcut chronosequence (0.5 to 60 years after harvesting) in the laurel forest of La Palma island (Canarian Archipelago) to determine the recovery of the stands with respect to species composition, richness, life strategies and structural parameters of the canopy. Multivariate analysis showed that exotic species, as well as annual ruderal species were confined to early-successional stages, while native perennials, typical of laurel forests, dominated the late-successional stages. Total species richness decreased significantly with time after clear-cutting. The relative fast recovery of understory native species may be due to low forest floor disturbance during harvesting. Shade-intolerant pioneer, pioneer-remnant and shade-tolerant late-successional species were the main life strategies of native tree species. Most structural parameters showed a continuous and monotonic increase (basal area, biomass) or decrease (density, percentage of photosynthetic biomass) during succession. Once clear-cutting, here performed with an interval of 8 years, is abandoned, the recovery of the laurel forest seems possible due to careful logging that protects the soil and a rapid asexual regeneration of native tree species, revealing this to be a sustainable management practice. 相似文献
968.
The variability of fibre and ray dimensions was studied at three radial positions (10, 50 and 90% of radius) in 5 cork oaks (Quercus suber L.) approximately 40 years old. Uniseriate ray height and cell number as well as multiseriate ray height and width were measured in tangential sections. Fibre length, width and wall thickness were measured after maceration. The most striking features of cork oak wood were the large multiseriate rays and the frequent homocellular uniseriate rays. On average multiseriate rays were 5.16 mm high and 0.48 mm wide, and uniseriate rays contained 11 cells and were 227 μm high. Neighbour rays presented large dimensional differences but there was no radial variation and there were very small between-tree differences. The radial maintenance of high and wide rays was discussed as a means to improve water shortage in response to water stress. Fibre dimensions increased radially but differed little between trees: on average, 960–1,220 μm length, 18.40–21.49 μm width and 6.66–8.07 μm wall thickness. The ray pattern showed enough variation for visual appreciation while ensuring within and between-tree uniformity. The presence of rays has to be taken into consideration for designing wood drying programs. 相似文献
969.
Bio-guided isolation of the cytotoxic corytenchine and isocoreximine from roots of Annona cherimolia
Martínez-Vázquez M De la Cueva Lozano DG Estrada-Reyes R González-Lugo NM Ramírez Apan T Heinze G 《Fitoterapia》2005,76(7-8):733-736
The roots of Annona cherimolia have been shown to contain the known tetrahydroprotoberberine alkaloids corytenchine (1) and isocoreximine (2), investigated for their cytotoxic properties. 相似文献
970.
Variability in the content of active constituents and biological activity of Glycyrrhiza glabra 总被引:1,自引:0,他引:1
Nine samples of Glycyrrhiza glabra were collected in various sites of Calabria, Italy, with the aim to determine the variability in the confront of active constituents and in antibacterial and antifungal activities of the extracts. The samples showed remarkable differences in chemical composition and biological activity. 相似文献