Studies on the degradative ability of the blue stain fungus Lasiodiplodia theobromae (Pat.) Griffon ' Maublanc have shown several strains to cause significant weight losses (c. 20%) in wood of temperate and tropical species, aspen (Populus tremula) and rubberwood (Hevea brasiliensis), both species that commonly form tension wood. In addition to the consumption of soluble carbohydrates, major changes occurred in the ultrastructure of fibre cell walls, with a rapid attack of the G-layer of the gelatinous fibres. Following G-layer degradation, earlywood fibres of both species showed true cell wall degradation with pronounced erosion attack, suggesting that prior destruction of the G-layer afforded greater accessibility and ease of attack of the outer secondary cell wall layers.
RESUMENSe determinó en condiciones de laboratorio el efecto microbiológico de los metabolitos secundarios, desarrollados como mecanismo de defensa pasiva, en la madera de las especies Puy (Tabebuia serratifolia (Vahl.) Nicholson), Zapatero (Peltogyne porphyrocardia Griseb.), Algarrobo (Hymenaea courbaril L.) y Cartan (Centrolubium paraense Tul. var. orinocense Benth), frente a dos de los más comunes microorganismos que causan deterioro de la madera G. traveum y T. versicolor. El ensayo microbiológico se realizó empleando el método de dilución en gel con inoculación superficial en placa. Se evaluaron tres tipos de solventes de diferente polaridad para la recuperación de los extractivos (acetona, etanol y agua). Se empleó agar extracto de malta como medio de cultivo a tres niveles de concentración de extractivo (0,05%, 0,1% y 0,2% v/v). La inhibición del crecimiento, fue utilizada como una medida para evaluar la efectividad del producto químico natural. Los resultados obtenidos de la evaluación preliminar demostraron que todos los extractos evaluados presentan actividad biológica asociada con los microorganismos de prueba. El perfil de la actividad antifúngica del extracto soluble en agua, sostiene que es el más tolerable por los microorganismos que deterioran la madera, posiblemente atribuido a la presencia de materiales orgánicos señalados como azúcares del duramen. Los extractos acetónicos y etanólicos demostraron tener la capacidad de extraer la mayor cantidad de compuestos biológicamente activos del duramen de las especies evaluadas, al producir elevados niveles de control en el crecimiento de los microorganismos empleados en el estudio. PALABRAS CLAVE:Actividad antifúngica, duramen, extractivos, metabolitos secundarios, productos naturales. ABSTRACTThe microbiological effect of the secondary metabolites developed as mechanism of passive defense, in the wood of the species Puy (Tabebuia serratifolia (Vahl.) Nicholson), Zapatero (Peltogyne porphyrocardia Griseb.), Algarrobo (Hymenaea courbaril L.) and Cartan (Centrolubium paraense Tul. var. orinocense Benth) was evaluated under laboratory conditions, against two common microorganisms that cause deterioration on the wood G. traveum and T. versicolor. Antifungal assay was carried out using the agar dilution method with superficial inoculation. Solvents, like acetone, ethanol and water, of different polarity were evaluated for the recovery of the extractives. Malt extract agar was used in the antifungal assay at concentration of 0,05%, 0,1% and 0,2% (v/v). The growth inhibition was used as a measure to evaluate the effectiveness of the natural chemical product. Results of the preliminary evaluation demonstrated that all the evaluated extracts present biological activity associated with the microorganisms test. The antifungal activity of the soluble extract in water, sustains that it is the most tolerant for the microorganisms that deteriorate wood. This may be attributed to the presence of organic materials called heartwood´s sugar. The acetonic and ethanolic ext...
O livro traz conceitos básicos da epidometria florestal, suas funções, resultados esperados e demais ferramentas utilizadas neste campo.
Losses in toughness correlated with losses in weight were found in birch (Betula verrucosa), Scots pine (Pinus sylvestris) and Caribbean pine (Finns caribaea var. hondurensis) over a six months period after inoculation with the blue stain fungus Lasiodiplodia theobromae. Differences between wood samples loaded radially and tangentially in the toughness testing device were not found, probably because the size of the samples (10 10 x 100mm) was smaller than that specified in standards. Higher strength losses at later stages of incubation were strongly correlated with degree of degradation of parenchyma cells producing weak planes of brash fracture and abrupt transwall failure. Transwall failure revealing the S 2 microfibrillar angle in early stages of incubation and a very smooth surface in more advanced stages of incubation, were also observed. Vessels in birch showed transwall failure after initial failure following degraded terminal parenchyma cells. Intrawall failure was also observed, particularly between the S,-S 2 interface. Results indicate that this stain fungus could have a negative effect on the mechanical wood properties of the hard-and softwoods studied.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.