Propagação vegetativa de Brosimum gaudichaudii Tréc. (mama-cadela) por estacas de raízes / Vegetative propagation of Brosimum gaudichaudii Tréc. (mama-cadela) by root cuttings

Brosimum gaudichaudii Tréc. (mama-cadela) é uma planta medicinal nativa do Cerrado, utilizada na medicina tradicional. O objetivo deste trabalho foi verificar a possibilidade de propagação de mama-cadela por meio de estacas de raízes, sob o efeito de reguladores de crescimento e de diferentes substratos. No experimento 1 foram avaliados os efeitos da aplicação de ácido indol-butírico (AIB) e ácido naftaleno-acético (ANA) na concentração de 1000 mg L-1 e três substratos (S1- areia; S2 - 75 por cento de areia + 25 por cento de substrato comercial; S3 - 50 por cento de areia + 50 por cento de substrato comercial). No experimento 2 foram avaliadas 4 doses de AIB: 0 - testemunha; 250 mg L-1 (1,3426 mM ); 500 mg L-1 (2,6853 mM) e 1000 mg L-1 (5,3706 mM); e 4 doses de ácido naftaleno-acético (ANA): 0 - testemunha; 250 mg L-1 (1,2295 mM); 500 mg L-1 (2,458 mM); e 1000 mg L-1 (4,918 mM). O delineamento experimental utilizado foi de blocos ao acaso com três repetições de seis estacas por parcela. No experimento 1, os substratos compostos por areia e areia (75 por cento) + substrato comercial (25 por cento) proporcionaram os maiores Índices de pegamento. A aplicação de AIB (1000 mg L-1) proporcionou aumentos relativos de 30,8 por cento e 51,3 por cento, no IMP quando comparada com a testemunha e a aplicação de ANA, respectivamente. No experimento 2, observou-se resposta quadrática significativa da aplicação de AIB sobre o IMP. A dose de 500 mg L-1 (2,6853 mM) promoveu maior IMP. Não houve efeito significativo das doses de ANA para os parâmetros avaliados. Não houve efeito significativo relevante de substratos ou hormônios sobre os demais parâmetros avaliados. Estes resultados evidenciam o potencial de utilização de estacas de raiz de mama-cadela para a produção de mudas clonais desta espécie.

Brosimum gaudichaudii Tréc. (mama-cadela) is a medicinal plant native to Cerrado and largely used in traditional medicine. The aim of this study was to verify the propagation of mama-cadela by means of root cutting under the effect of plant growth regulators and different substrates. In experiment 1, the effects of indole butyric acid (IBA) and naphthylacetic acid (NAA) at the concentration of 1000 mg L-1 were evaluated together with three substrates (S1 - sand; S2 - 75 percent sand + 25 percent commercial substrate; S3 - 50 percent sand + 50 percent commercial substrate). In experiment 2, 4 IBA levels were evaluated: 0 - control; 250 mg L-1 (1.3426 mM ); 500 mg L-1 (2.6853 mM) and 1000 mg L-1 (5.3706 mM), as well as 4 NAA levels: 0 - control; 250 mg L-1 (1.2295 mM); 500 mg L-1 (2.458 mM) and 1000 mg L-1 (4.918 mM). The adopted experimental design was in randomized blocks with three replicates of six cuttings per plot. In experiment 1, substrates containing sand and sand (75 percent) + commercial substrate (25 percent) promoted the highest average rooting indexes. Application of IBA (1000 mg L-1) led to increases of 30.8 percent and 51.3 percent in the average rooting indexes compared to control and NAA application, respectively. In experiment 2, there was a significant quadratic response of IBA application on the average rooting index. The level of 500 mg L-1 (2.6853 mM) promoted the highest average rooting index. There was no significant effect of NAA levels for the evaluated parameters. Similarly, there was no significant effect of substrates or hormones on the remaining parameters evaluated. These results show the potential use of mama-cadela root cuttings for the production of clonal seedlings of this species.

Radon dynamics and reduction in an underground mine in Brazil. Implications for workers' exposure.

This work was aimed at studying the behaviour of 222Rn in an experimental underground copper mine in Brazil with a single entrance. The 222Rn concentrations, meaured by using a dynamic radon measuring technique. varied between 30.5 Bq.m(-3), during ventilated conditions applied to the mine galleries, and 19.4 x 10(3) Bq.(-3) for non-ventilated conditions and when operational mining activities were conducted inside. High radon concentration surges were observed after blasting and drilling activities. In the cases of inadequate ventilation, it was estimated that workers could be subjected to exposures as high as 10 microSv.h(-1), only due to 222Rn and its short-lived progeny. The results show the importance of real-time measurements to evaluate radon dynamics during mining operations.

Radon flux at King George Island, Antarctic Peninsula.

Fluxes of 222Rn from the ice-free terrain to the atmosphere were measured directly, for the first time, at the Brazilian Antarctic Station Ferraz during the summer field campaign of 1998/99. Average value for the flux was 7.7 +/- 4.8 x 10(-2) atoms cm(-2) s(-1) and it ranged between 0.21 x 10(-2) atoms cm(-2) s(-1) and 28 x l0(-2) atoms cm(-2) s(-1). The average flux of 220Rn was estimated to be 23 atoms cm(-2) s(-1), using a combination of two techniques: nuclear track detection and alpha spectrometry of radon daughters. It was found that the production of radon by uranium (41.54 + /-7.17 Bq kg(-1)) and thorium (57.97 +/- 12.14 Bq kg(-1)) equivalent soil contents, and a diffusion coefficient derived from experimental data for the local terrain could account for this average flux. Nevertheless, the large surges of 222Rn in the atmosphere frequently observed for that area could not be explained by this flux only.

Kinetic studies of lipase from Candida rugosa: a comparative study between free and immobilized enzyme onto porous chitosan beads.

The search for an inexpensive support has motivated our group to undertake this work dealing with the use of chitosan as matrix for immobilizing lipase. In addition to its low cost, chitosan has several advantages for use as a support, including its lack of toxicity and chemical reactivity, allowing easy fixation of enzymes. In this article, we describe the immobilization of Candida rugosa lipase onto porous chitosan beads for the enzymatic hydrolysis of olive oil. The binding of the lipase onto the support was performed by physical adsorption using hexane as the dispersion medium. A comparative study between free and immobilized lipase was conducted in terms of pH, temperature, and thermal stability. A slightly lower value for optimum pH (6.0) was found for the immobilized form in comparison with that attained for the soluble lipase (7.0). The optimum reaction temperature shifted from 37 degrees C for the free lipase to 50 degrees C for the chitosan lipase. The patterns of heat stability indicated that the immobilization process tends to stabilize the enzyme. The half-life of the soluble free lipase at 55 degrees C was equal to 0.71 h (Kd = 0.98 h(-1)), whereas for the immobilized lipase it was 1.10 h (Kd = 0.63 h(-1)). Kinetics was tested at 37 degrees C following the hydrolysis of olive oil and obeys the Michaelis-Menten type of rate equation. The Km was 0.15 mM and the Vmax was 51 micromol/(min x mg), which were lower than for free lipase, suggesting that the apparent affinity toward the substrate changes and that the activity of the immobilized lipase decreases during the course of immobilization.