Uptake of insecticides and fungicides by impregnable and refractory coniferous wood species treated with commercial bio-based emulsion gel formulations

Even in dry state, wood can be prone to biological degradation. Preservation is a prerequisite to confer protection and durability to wood. This is conventionally achieved by impregnating the wood with pesticides. A key point in these treatments is the complex process of wood penetrability. We focused on the relation between the penetration of wood preservatives, wood microstructure, and the physical characteristics of formulations in the impregnation of the easily impregnable pine (Pinus sylvestris), and the refractory spruce (Picea abies). In this work, specimens from the two species were impregnated with three types of commercial bio-based emulsion gels formulations containing insecticides and fungicides. The effect of treatment method using dipping, surface spraying, and vacuum-impregnation, on the retention of the active agents was analyzed. Visual assessment, and qualitative and quantitative analyses of cypermethrin, permethrin and  propiconazole by gas liquid chromatography coupled to mass spectroscopy showed enhanced penetration of the active agents, and revealed differences of penetration performance of each agent. The suitable combinations of solvents and surfactants used in the bio-based formulations enabled rapid wood penetration and high yields retention. The capacity of penetration and retention of our gel formulations is discussed in terms of the connectivity of the conducting cells network of the two wood species

The wood cell wall at the ultrastructural scale formation and topochemical organization

The macromolecular organization of the secondary wall of the cells from tree xylem is in large part responsible for the mechanical and physiological properties of wood. Modeling secondary walls of wood is difficult because information about their macromolecular architecture at the ultrastructural scale is missing. Numerous microscopic studies have provided views of the lignocellulosic composite material, but nanoscale distribution of the polymers and their interaction in muro is still not clearly understood. The intimate macromolecular organization of cell walls is defined during their differentiation. It is at the stage of wall thickening corresponding to secondary wall development that the topochemical organization and the interactions between cellulose, hemicelluloses and lignin are established.Using the conjunction of the high resolution of transmission electron microscopy (TEM) and the specificity of immunological probes directed against the main cell wall polymers, we investigated the deposition of hemicelluloses and lignins from the early stage of cambium differentiation to the mature fiber and vessel walls in growing model plants of Arabidopsis thaliana and poplar. TEM examination of differentiating cells as well as various wood and wood –derived materials and genetic plant mutants brought multiple evidence of the lamellar sub-organization of the secondary walls. Immuno-gold labeling showed that two structurally different xylan types were deposited at different stages in the wall thickening. Similarly two different types of lignin molecules were shown to be differentially polymerized at different steps of the building of the wall, lignin molecules of the condensed type being first deposited at the earliest stage of secondary thickening before the non-condensed  types. This process may be modified in response to environmental factors, as in tension wood.The spatio-temporal relationships occurring between hemicelluloses, lignin and cellulose microfibrils (CMFs) during the secondary wall development suggest that xylans with less substituted chains would be more directly interacting with CMFs than those with higher substitution patterns. It also suggests that lignin molecules of the non-condensed type have a function in bringing cohesion between the lamellae of CMFs. A model of wall assembly during secondary thickening is proposed

Molecular phenotyping of the pal1 and pal2 mutants of Arabidopsis thaliana reveals far-reaching consequences on phenylpropanoid, amino acid, and carbohydrate metabolism

The first enzyme of the phenylpropanoid pathway, Phe ammonia-lyase (PAL), is encoded by four genes in Arabidopsis thaliana. Whereas PAL function is well established in various plants, an insight into the functional significance of individual gene family members is lacking. We show that in the absence of clear phenotypic alterations in the Arabidopsis pall and pal2 single mutants and with limited phenotypic alterations in the pall pal2 double mutant, significant modifications occur in the transcriptome and metabolome of the pal mutants. The disruption of PAL led to transcriptomic adaptation of components of the phenylpropanoid biosynthesis, carbohydrate metabolism, and amino acid metabolism, revealing complex interactions at the level of gene expression between these pathways. Corresponding biochemical changes included a decrease in the three major flavonol glycosides, glycosylated vanillic acid, scopolin, and two novel feruloyl malates coupled to coniferyl alcohol. Moreover, Phe overaccumulated in the double mutant, and the levels of many other amino acids were significantly imbalanced. The lignin content was significantly reduced, and the syringyl/guaiacyl ratio of lignin monomers had increased. Together, from the molecular phenotype, common and specific functions of PAL1 and PAL2 are delineated, and PAL1 is qualified as being more important for the generation of phenylpropanoids

Studies on the determination of structural characteristics of three types of hemicelluloses

Part I of this thesis describes the isolation and purification of the principal hemicellulose from the reed Arundo donax, Monocotyledon/ Gramineae. By use of the classical techniques, a structural investigation demonstrated that this hemicellulose is an arabino-4-0-methy1-glucuronoxylan with on average 10 arabino-furanose residues and 5 4-O-methyl-glucopyranuronic acid residues occurring as branch points with respectively α(l→3) and α (l→2) linkages on the β(1→4) linked backbone of xylopyranosyl residues. The results of periodate oxidation, methylation and osmometry agreed well in demonstrating an average degree of polymerization of approximately 80. Enzymic hydrolysis of the polysaccharide with an endoxylanase of known specificity for β (l→4) xylosidic bonds showed that the anomeric nature of the linkages between the xylose units was of the β configuration. P.m.r. spectroscopy of the permethylated polysaccharide confirmed the above result by showing a strong doublet at p.p.m. 4.24 δ(J 6.5 Hz) corresponding to a β linkage, and a peak at p.p.m. 5.53 β corresponding to α anomers. The structure of the polysaccharide was deduced to be of the following form : [diagram omitted]. In Part II, the isolation of the hemicelluloses from the wood of Redwood, Sequoia sempervirens, has been carried out by the use of different methods. Timell's method using the solubility differences of the hemicelluloses between potassium hydroxide and sodium hydroxide allowed the isolation of a glucomannan which was easily purified by barium hydroxide complexation. For the separation of xylan from galactoglucomannan, a delignification of the polysaccharide mixture was necessary. Purification of the acidic xylan was achieved by complexation with cetyltrimethylammonium salt,also allowing the recovery of a galactoglucomannan which was further purified by selective precipitations with barium hydroxide. The structure of the xylan was determined with emphasis on the methylation procedure. It is demonstrated that repeated Hakomori methylations on an acidic xylan can be performed without degradation of the main chain. The structural features of the xylan consist of a xylosyl backbone with an average degree of poly merization of about 55 and carrying on average one 4-0_-methyl glucuronic acid residue for four xylose residues and one arabinofuranooe residue every 20 xylose residues. A study of the localization of the uro nic acid substituents was carried out with the use of a specific xyla-nase and was shown not to be randomly distributed on the xylosyl main chain. The structures of the glucomannan and galactoglucomannan are also described. Both present the customary structure taht is a β(1→4) linked glucomannan with, in the latter case, some side chain galactose units (1→6) linked to the main chain. [diagram omitted] The results are compared to the data reported in similar hemicelluloses from coniferous woods and the literature for show that in the present wood the ratio of mannose to glucose is unusually high. The validity of the methods of isolation of these polysaccharides is discussed and it is demonstrated that there is a great heterogeneity concerning the composition of the galactoglucomannans present in this wood. In Part III, the cell wall carbohydrate composition of a one-month-old stem from Arundo donax was established for tissues at different stages of maturity. There is a relationship between the increase in xylose and glucose content, the decrease in arabinose and galactose content, together with the elongation of the fibres. Similar changes were also found at the level of one elongating internode. These variations are interpreted in terms of polysaccharide deposition in the cell wall of the fibres with maturatioa. Each internode appears as a physiological unit where the progressive fibrous character of the tissues corresponds to a characteristic cell wall polysaccharide composition. The isolation and purification of the arabino-4-0- methyl-glucuronoxylans, by stepwise alkaline extraction from tissues at three different stages of maturity, revealed that the main change in the hemi-cellulose's structure according to growth is in the increase of the degree od polymerization. As the plant matures the average chain length of the xylan increases from about 60 in the youngest internodes to about 150 in the older ones. The structural features of the xylan which is already present in the youngest tissues are the same regardless of the age of the tissues. More subtle differences, such as the modification of the substituents occurring on the xylan backbone, were found in the acetyl distribution which increases, and in the presence of 4-0-methyl substituents on the glucuronic acids which decreases as the plant ages. In all cases examined, the xylose and xylan content of the tissues reaches a maximum value in the intermediate stage of the maturation and then decreases. The isolation of an exo-xylanase in the corresponding tissues suggests that xylans are not only structural polysaccharides but also can act as reserve elements.Science, Faculty ofChemistry, Department ofGraduat

Uptake of insecticides and fungicides by impregnable and refractory coniferous wood species treated with commercial bio-based emulsion gel formulations

Even in dry state, wood can be prone to biological degradation. Preservation is a prerequisite to confer pro-tection and durability to wood. This is conventionally achieved by impregnating the wood with pesticides.A key point in these treatments is the complex process of wood penetrability. We focused on the relation between the penetration of wood preservatives, wood microstructure, and the physical characteristics of formulations in the impregnation of the easily impregnable pine (Pinus sylvestris), and the refractory spruce (Picea abies). In this work, specimens from the two species were impregnated with three types of commercial bio-based emul-sion gels formulations containing insecticides and fungicides. The effect of treatment method using dipping, surface spraying, and vacuum-impregnation, on the retention of the active agents was analyzed. Visual assess-ment, and qualitative and quantitative analyses of cypermethrin, permethrin and propiconazole by gas liquid chromatography coupled to mass spectroscopy showed enhanced penetration of the active agents, and revealed differences of penetration performance of each agent. The suitable combinations of solvents and surfactants used in the bio-based formulations enabled rapid wood penetration and high yields retention. The capacity of penetration and retention of our gel formulations is discussed in terms of the connectivity of the conducting cells network of the two wood specie