ABSTRACT
ABSTRACT High toxicity of the preservatives most frequently used in wood treatment and the resulting risks of handling pose a threat to small producers and to the environment. In an attempt to mitigate these problems, the present study was conducted with the objective of evaluating the preservative effect of tannic extract on biodeterioration of Acacia mearnsii wood. For this purpose, untreated and preserved specimens, some with tannin extract and some with a preservative mixture based on CCB (Chromated Copper Borate), were submitted to accelerated rotting trials with the fungus that causes white rot (Pycnoporus sanguineus) for 16 weeks. The evaluations were made with a basis on weight loss and chemical components analysis, and they showed that the natural resistance of Acacia wood is moderate when exposed to the white rot fungus. The tannin concentrations showed similar effects to those of the CBB mixture in all evaluations, i.e., they significantly increased the biological resistance of the material, which started to be classified as very resistant to the fungus. Overall, the results suggest that tannin can be considered as a potential natural preservative product.
Subject(s)
Tannins/pharmacology , Wood/drug effects , Biodegradation, Environmental/drug effects , Acacia/microbiology , Pycnoporus/drug effects , Pycnoporus/physiologyABSTRACT
Podocarpus lambertii Klotzsch ex Endl. (Podocarpaceae) is native and a member of the Pinophyta (Gymnosperm) of southern Brazil, locally known as "pinheiro-bravo". The present work aims to investigate the effects of petroleum on the tracheids dimensions. Wood samples from twenty individuals were studied along the stem, ten being exposed to pollution and ten used as a control set. The wood samples were collected from incisions at three levels: at the ground level, and one and two metres above the ground level. From these samples, sub-samples were selected at the border of the growth layers in the vascular cambium-medulla direction. The methodology followed that traditionally recommended for plant anatomy studies, with analyses done by light microscopy (OLYMPUS - BX41) assisted by the software Image Pro-plus for measurements. Comparison of the individuals exposed to petroleum with the control set, showed that the length, diameter and cell wall width of the tracheids of the former were smaller, a trend which was statistically significant according to the Student's t-test. These traits were observed mainly on the tracheids of the last growth layer, corresponding to the year in which the individuals were exposed to petroleum.
Podocarpus lambertii Klotzsch ex Endl. (Podocarpaceae), popularmente conhecida por pinheiro-bravo, é uma espécie que pertence ao pequeno grupo de Pinophyta (Gimnospermas) nativas da região Sul do Brasil. O presente estudo teve como objetivo investigar os efeitos da poluição por petróleo nas dimensões das traqueídes que compõem o lenho dessa espécie. Para tanto, amostras do lenho de vinte indivíduos foram coletadas, dez deles expostos à poluição por petróleo e dez usados como controle (coletados em região livre de contaminação). As amostras foram obtidas por meio de incisões paralelas à superfície do solo em três alturas (nível do solo, 1 metro e 2 metros do nível do solo). As subamostras para o estudo da variação estrutural do lenho foram selecionadas no limite das camadas de crescimento no sentido câmbio-medula. A metodologia utilizada para desenvolver o trabalho foi aquela tradicionalmente recomendada para estudos em anatomia vegetal. As mensurações das traqueídes em material macerado, como comprimento, diâmetro e espessura da parede celular, foram feitas pelo software Image Pro-plus em Fotomicroscópio (OLYMPUS - BX41). Nos indivíduos expostos à poluição, o comprimento, diâmetro e espessura da parede das traqueídes foram menores quando comparados aos indivíduos controle e demonstraram diferenças estatisticamente significativas pelo teste t-student. Essas tendências foram observadas, principalmente, nas traqueídes da última camada de crescimento, correspondente ao ano em que os indivíduos permaneceram expostos ao petróleo.