Maria Beatriz de Oliveira Monteiro

A supramolecular proposal of lignin structure and its relation with the wood properties

In spite of the great importance of cellulose the lignin is considered the second most abundant substance of the wood. However, little attention has been given it, mainly to wood properties. The lignin as well as other structural compounds (cellulose and hemicelluloses), has obviously an important role on the wood properties, probably due its composition and existent bonds. In general lignins have beta-O-4 (Alkyl Aril Ether) as majoritary bond. This bond in a continued structure form big molecules with spiral conformation as virtual model. Based on this idea, lignins that have high/low beta-O-4 content may have differentiated spiraled structures,suggesting different behaviors on the wood properties,which shows that the lignins (Guaicyl:Syringyl (GS)) of angiosperms, for example, which have higher beta-O-4 content would present higher spiral conformation than gymnosperms lignins(HG). On the other hand HG lignins have chance of being more anchored on the matrix compound than GS lignins. In this context, the beta-O-4 bonds of lignins possibly affect the wood properties, therefore, it is considered relevant for wood technology science discussion.

VARIAÇÃO LIGNO-ANATÔMICA EM MUDAS DE Eucalyptus grandis (Hill ex Maiden) TRATADAS COM REGULADORES DE CRESCIMENTO

Neste trabalho, objetivou-se analisar a relacao dos reguladores de crescimento GA3 e BAP na lignificacao e, consequentemente no diâmetro das fibras de plantas de Eucalyptus grandis aos seis meses de idade. Estudos anatomicos, bioquimicos e geneticos em decorrencia da aplicacao exogena de reguladores de crescimento na fase de desenvolvimento do vegetal, tem sido cada vez mais enfatizados. Alguns desses estudos tem obtido avanco no que se refere a interacao dos hormonios vegetais em relacao a anatomia e ao processo de lignificacao. A aplicacao dos reguladores de crescimento GA3 e BAP foi realizada isoladamente ou combinados nas respectivas concentracoes: GA3 (49,13 µM e 98,26 µM); BAP (111 µM e 222 µM), em mudas de Eucalyptus grandis ate seis meses de idade. Analises quimicas e anatomicas foram realizadas com o segmento caulinar das plantas tratadas. Para quantificar o teor de lignina pelo metodo Klason, as amostras foram livres para a retirada de extrativos e proteinas. Para a mensuracao do diâmetro das fibras, as amostras, apos sua dissociacao, foram analisadas por microscopia otica. O teor de lignina variou entre 23,37 a 29,64% e o diâmetro de fibra variou entre 13,33 a 20,39 µm. Tambem, pelos resultados, foi possivel visualizar, com o tratamento G[1] (49,13 de GA3 com 111µM de BAP) que o teor de lignina reduziu em 21,2% em relacao ao controle, e o C[1] diâmetro de fibra obteve o menor aumento em relacao aos outros tratamentos.

Alterações ligno-anatômicas em Solanum gilo Raddi por aplicação de cálcio e boro como estratégia de defesa

As plantas lenhosas, de maneira geral, possuem alto teor de lignina, podendo alcancar valores entre 25 a 35% em relacao a massa seca. Valores normalmente encontrados nas plantas arboreas. Algumas plantas jovens ou de habitos de crescimentos inferiores aos arbustivos possuem baixo teor de lignina, neste sentido, buscando superar os atuais niveis de lignificacao, foram testados em plantas fatores exogenos de estimulacao. Um sistema enzimatico complexo e responsavel pela formacao biossintetica dos precursores intermediarios da lignina, entretanto as peroxidases sao responsaveis pela fase determinante da polimerizacao na parede celular, cuja atividade foi pressupostamente modificada atraves da aplicacao de calcio e boro, visando aumentar a resistencia da planta aos fatores bioticos e abioticos, entre outros. Para tal, utilizou-se a especie Solanum gilo (familia Solanaceae) cultivar Portugues como planta experimental sob varios tratamentos, monitorando as aplicacoes quinzenal e semanalmente, nas formas simples e multiplas de aplicacao de CaSO4, H3BO3, CaCl2 e H3BO3/CaSO4, CaSO4/CaCl2, CaCl2/ H3BO3 e CaSO4/H3BO3/CaCl 2. O tratamento CaSO4/CaCl2, estatisticamente avaliado, induziu as plantas a uma taxa de lignificacao equivalente ao teor de lignina de 19%, superando a testemunha que apresentou 14 %. Modificacoes anatomicas foram tambem observadas nos elementos de vaso e fibras no que tange ao comprimento, diâmetro e espessura da parede celular. A quantificacao da lignina foi realizada segundo o metodo de Klason. A espectroscopia no infravermelho foi utilizada para analise composicional, revelando a existencia de modificacao da composicao de lignina guaiacilica da planta testemunha (G:S), 1,2:1 para lignina siringilica (G:S), 0,8:1 nas plantas que receberam o tratamento (CaSO4/CaCl2) quinzenal e semanalmente, respectivamente.

LIGNIFICAÇÃO E CRESCIMENTO DE Eucalyptus grandis (HILL EX MAIDEN) COM GA3 E BAP

In this research experiments were accomplished with two classes of vegetable hormones (gibberellin and cytokinin); with the objective of verifying the effect of gibberellic acid and 6-Benzylaminopurine (GA 3 and BAP) on the lignification and the longitudinal growth in seedlings of Eucalyptus grandis . The experiment was accomplished greenhouse, where were the growth regulators combined or isolated applied, in the following concentrations: GA 3 (49.13 μM e 98.26 μM); BAP (111 μM e 222 μM), with five repetitions for each treatment. The comparisons among the averages of the height of the plants to the 6 months showed that the most pronounced prolongations of the stem corresponded to the treatments G [2] , G [2] C [1] and G [2] C [2] where the largest concentration of GA 3 was used. In the treatment G [1] C [1] where it was combined to smallest concentration of GA 3 with to smallest concentration of BAP (49,13 μM de GA 3 + 111 μM de BAP), it happened the smallest lignin tenor 23,37%.

Cellular wall of Eucalyptus grandis under influence of growth regulators - chemical-anatomical aspects.

This research was caried out to understand the behavior of growth regulators (giberelic acid (GA3) e 6-benzilaminopurin (BAP) on lignification system of Eucalyptus grandis (FORMER Hill Maiden). After GA3 (alone) and BAP (combined) applications, analyses were carried out. These regulators were applied by a atomization system at different concentrations levels. Anatomical analysis, including Maule and Wiesner test as well as chemical analysis such as insoluble (Klason) and dioxane lignin were carried out as well. Infrared spectroscopy, methoxyl determination (Seizel Method) and total protein (Kjedahl Method) were performed. Synergism was suggested for G[1]C[1] treatment, at following concentrations: 49,13 μM and 111 μM. These treatments decreasing around 20% of lignin. In spite of infrared spectra that showed G/S composition, lignin GS, HG were confirmed by methoxyl content, suggesting regulators action on lignin biosynthesis and lignin structural modification. Positive Maule and Wiesner test were observed, while protein did not modified significatively.