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Wood is a major pool of organic carbon that is highly resistant to decay, owing largely to the presence of lignin. The only organisms capable of substantial lignin decay are white rot fungi in the Agaricomycetes, which also contains non-lignin-degrading brown rot and ectomycorrhizal species. Comparative analyses of 31 fungal genomes (12 generated for this study) suggest that lignin-degrading peroxidases expanded in the lineage leading to the ancestor of the Agaricomycetes, which is reconstructed as a white rot species, and then contracted in parallel lineages leading to brown rot and mycorrhizal species. Molecular clock analyses suggest that the origin of lignin degradation might have coincided with the sharp decrease in the rate of organic carbon burial around the end of the Carboniferous period.

Physical, chemical, and biological properties of wood depend largely on the properties of cellulose, noncellulosic polysaccharides, and lignin, and their assembly mode in the cell wall. Information on the assembly mode in the main part of the ginkgo tracheid wall (middle layer of secondary wall, S2) was drawn from the combined results obtained by physical and chemical analyses of the mechanically isolated S2 and by observation under scanning electron microscopy. A schematic model was tentatively proposed as a basic assembly mode of cell wall polymers in the softwood tracheid as follows: a bundle of cellulose microfibrils (CMFs) consisting of about 430 cellulose chains is surrounded by bead-like tubular hemicellulose-lignin modules (HLM), which keep the CMF bundles equidistant from each other. The length of one tubular module along the CMF bundle is about 16 +- 2 nm, and the thickness at its side is about 3 - 4 nm. In S2, hemicelluloses are distributed in a longitudinal direction along the CMF bundle and in tangential and radial directions perpendicular to the CMF bundle so that they are aligned in the lamellae of tangential and radial directions with regard to the cell wall. One HLM contains about 7000 Csub(6)-Csub(3) units of lignin, and 4000 hexose and 2000 pentose units of hemicellulose.

Primary pyrolysis reactions and relative reactivities for depolymerization and condensation/carbonization were evaluated for various lignin model dimers with α-O-4, β-O-4, β-1, and biphenyl substructures by characterizing the tetrahydrofuran (THF)-soluble and THF-insoluble fractions obtained after pyrolysis at 400°C. Reactivity was quite different depending on the model structure: depolymerization: α-O-4 [phenolic (ph), nonphenolic (nonph)], β-O-4 (ph) > β-O-4 (nonph), β-1 (ph, nonph) > biphenyl (ph, nonph); condensation/carbonization: β-1 (ph) > β-O-4 (ph) > α-O-4 (ph) > β-O-4 (nonph), biphenyl (ph, nonph), α-O-4 (nonph), β-1 (nonph). Major degradation pathways were also identified for β-O-4 and β-1 model dimers: β-O-4 types: Cβ-O cleavage to form cinnamyl alcohols and phenols and Cγ-elimination yielding vinyl ethers; β-1 types: Cα-Cβ cleavage yielding benzaldehydes and styrenes and Cγ-elimination yielding stilbenes. Relative reactivities of these pathways were also quite different between phenolic and nonphenolic forms even in the same types; Cβ-O cleavage (β-O-4) and Cγ-elimination (β-1) were substantially enhanced in phenolic forms.

A new approach is proposed for the evaluation of the brittleness of heat-treated Styrax tonkinensis wood. Heat treatment made wood more brittle when wood was heated at a higher temperature or for a longer time. The brittleness increased to four times that of the control when wood was heated at 200°C for 12 h. For treatment at 160°C, the increase in brittleness without any change in weight is thought to be possibly caused by the relocation of lignin molecules. At higher temperatures, loss of amorphous polysaccharides due to degradation is thought to become the main factor affecting brittleness. The crystallites that were newly formed after 2 h of treatment showed brittleness that was different from that of the inherent crystallites remaining after 12 h of heat treatment. This inherent crystalline cellulose possibly plays a role in brittleness. There is also the possibility of using color to predict the brittleness of heat-treated wood.

From two natural bamboo stands dominated by the bamboo species guadua (Guadua angustifolia Kunth) located in sites with different ecological conditions, culms were assessed in order to elucidate possible changes in physical- mechanical properties and lignin content as well. Test pieces were collected from the two sites and were obtained from guadua culms with ages between 1 and 5 years. Among sites the values obtained of physical-mechanical properties and lignin content tend to increase with culms age; however, these changes were not always significantly different (p>0.05). Those culms from the warmer and drier site located at lower altitude showed on average values significantly (p<0.05) higher of the variables assessed. Considering the results obtained, culm maturity is an important factor influencing both physical-mechanical properties and lignin content, however ecological conditions determine larger differences in these variables to be considered for selecting bamboo culms when specific attributes are required by the market.

Changes in leaf anatomy were evaluated in genotypes of Brachiaria brizantha, Brachiaria decumbens, Brachiaria ruziziensis and three Brachiaria ruziziensis clones through tissue proportion in internerval and midrib regions at three regrowth ages. Plants were grown and cutting was performed after 60 days. Further, leaves were sampled at 8, 15 and 29 regrowth days and processed with usual plant microtechnique. The internerval region showed higher parenchyma percentage at 15 days for Clone 95 and similar values at 15 and 29 days for Clone 1. The proportion of vascular bundles was lower after 15 days in Clones 1 and 95 and 29 days in B. brizantha. In the midrib, the parenchyma proportion was higher at 29 days in B. brizantha and lower at 15 days in B. ruziziensis. The proportion of vascular bundles was higher at 8 days in B. decumbens, B. brizantha and Clone 1, and lower at 29 days for Clones 97 and 95 and at 8 days in B. ruziziensis. Therefore, the regrowth age modifies the percentage of leaf tissues in Brachiaria genotypes, in which the fibers and vascular bundles increase at 29 days and 8-day-old leaves are not fully developed.

The objective of this experiment was to evaluate responses of soybean cultivars seeds (with different levels of lignin) considering harvest postponement under the incidence of water and the effect of storage. The experiment was conducted in Iraí de Minas, Brazil using a randomized block design with three replications under a 5 x 3 x 3 factorial arrangement, with five soybean cultivars (NK 7059 RR, SYN 1163 RR, SYN 9070 RR, AS 7307 RR and SYN 1283 RR), three harvesting periods (R8, R8 + one rain simulation in the pre-harvesting period and R8 + two simulations in the pre-harvesting period) under three storage times (0, 90 and 180 days). Seeds were evaluated for their chemical composition (lignin contents), the percentage of moisture damage using the tetrazolium test and physiological quality (germination, accelerated aging, conductivity test, seedling emergence and emergence index). Cultivar AS 7307 RR had the highest lignin content in the integument, the lowest percentage of damage by moisture and the highest physiological quality. Cultivars NK 7059 RR and SYN 1163 RR had the lowest lignin contents in the integument and the highest moisture damage. Electrical conductivity increased after storing all cultivars. Resumo: Objetivou-se com este trabalho avaliar o desempenho de sementes de cultivares de soja com diferentes teores de lignina considerando o retardamento da colheita sob incidência artificial de chuva, e ao longo do armazenamento. O ensaio foi conduzido em Iraí de Minas, MG, em blocos casualizados com três repetições e esquema fatorial 5 x 3 x 3, sendo cinco cultivares de soja (NK 7059 RR, SYN 1163 RR, SYN 9070 RR, AS 7307 RR e SYN 1283 RR), três épocas de colheita (R8, R8 + uma simulação de chuva na pré-colheita e R8 + duas simulações de chuva na pré-colheita), e três épocas de armazenamento (0, 90 e 180 dias). As sementes foram avaliadas quanto à composição química (teor de lignina), porcentagem de danos por umidade usando o teste de tetrazólio, e a qualidade fisiológica (germinação, teste de envelhecimento, condutividade elétrica, emergência, índice de emergência). A cultivar AS 7307 RR apresentou maior teor de lignina no tegumento, menor porcentagem de danos por umidade e melhor qualidade fisiológica. As cultivares NK 7059 RR e SYN 1163 RR apresentam menores teores de lignina no tegumento e maiores danos por umidade. Os valores de condutividade elétrica aumentam com o armazenamento para todas as cultivares.

Effects of side chain hydroxyl groups on pyrolytic β-ether cleavage of phenolic model dimers were studied with various deoxygenated dimers under pyrolysis conditions of N₂/400°C/1 min. Although phenolic dimer with hydroxyl groups at the C α - and C γ -positions was much more reactive than the corresponding nonphenolic type, deoxygenation at the C γ -position substantially reduced the reactivity up to the level of the nonphenolic type. These results are discussed with the cleavage mechanism via quinone methide intermediate formation, which is activated through intramolecular hydrogen bonds between C α - and C γ - hydroxyl groups.

The digestibility potential of leaves from forages depends on the amount of nutrition in their tissues, with low lignin deposition in the cell wall, mainly parenchyma and phloem. This research evaluated the leaf structure of different Urochloa genotypes and discussed its potential for evaluating digestibility. The cultivars U. brizantha, U. decumbens, U. ruziziensis and three clones of U. ruziziensis (1, 95 and 97), which are under development in breeding programs, were evaluated. Plants were grown under the recommended culture conditions for the Urochloa species. Plants were cut 60 days after sowing, and leaves were collected at 15 days of regrowth. Leaves were fixed in FAA 70 and further stored in 70% ethanol until being submitted to the usual microtechniques for the preparation of microscopy slides. The area of the tissues from the interveinal and midrib regions was measured using ImageJ software, and their proportions were calculated. In the interveinal region, the proportion of chlorophyll parenchyma was greater for U. decumbens and the Clone 1 genotypes. Urochloa brizantha and clones 95 and 97 showed a higher proportion of the vascular bundle compared to U. ruziziensis, U. decumbens and Clone 1. The proportion of the ground parenchyma in the midrib was greater in U. brizantha, Clone 95 and Clone 97. Thus, it can be concluded that the Clone 1 genotypes (from U. ruziziensis) showed leaf tissues (parenchyma and phloem) with higher digestibility potential; in addition, U. brizantha and U. decumbens showed a high percentage of xylem and sclerenchyma, which reduces their quality as forage. RESUMO: O potencial de digestibilidade das folhas de forrageiras depende da quantidade de seus tecidos com baixa deposição de lignina nas paredes celulares, principalmente o parênquima e floema. O presente trabalho objetivou avaliar a estrutura foliar de diferentes genótipos de Urochloa e seu potencial de digestibilidade foliar. Foram avaliadas as cultivares U. brizantha, U. decumbens, U. ruziziensis e três clones de U. ruziziensis (1, 95 e 97). As plantas foram cultivadas em campo com condições de manejo recomendadas para a espécie, sendo cortadas aos 60 dias e as folhas coletadas aos 15 dias de rebrota. As folhas foram fixadas em FAA 70, armazenadas em etanol 70% e posteriormente submetidas à microtécnica usual para preparação de lâminas semipermanentes. Foram analisadas as regiões internervural e da nervura mediana com o auxílio do software Image J sendo mensurada a área de cada tecido da folha e depois calculada a sua proporção em relação à área total das secções. Na região internervural, a proporção de parênquima foi maior em U. decumbens e no Clone 1. Ainda nesta região, Urochloa brizantha e os Clones 95 e 97 apresentaram maiores médias para a proporção de feixes vasculares. Na nervura mediana, a proporção do parênquima foi maior em U. brizantha, Clone 95 e Clone 97. De maneira geral, o Clone 1 (proveniente de U. ruziziensis) apresentou parênquima e floema em maiores proporções, enquanto genótipos de U. brizantha e U. decumbens demonstram altas quantidades de xilema e esclerênquima que reduzem o seu potencial de digestibilidade.