Flax Stem Research Articles

Improvement of flax husk production technology as raw material for cellulose nanomaterials

Experimental studies on ultrasonic dispersion of the organic complex of flax stem in the voiced medium on the installation of continuous operation IUSD-01 were carried out, flax fiber with high quality indicators was obtained.

Інтенсифікація внутрішнього тепломасопереноса при переробці сировини рослинного походження

The basis for the creation of energy-efficient environmentally-friendly technologies is the intensification of heat and mass transfer processes, since the drying processes of materials are the most energy-intensive and in many cases limit the capacity of the entire production line. And, as a rule, intensification of the drying process as a whole is not possible without the acceleration of internal mass transfer. The purpose of this study is to determine the effect of temperature and solution properties on the intensification of capillary impregnation in the industrial preparation of flax trust. The raw material for the preparation of flax trust, from which flax fiber is obtained, is flax straw. The flax stem is covered with a cuticle - a thin waxy film outside. The fiber bundles in the flax stem are clearly separated. The thin primary walls of adjacent elementary fibers are interconnected by an intercellular substance composed mainly of pectin, part of which is soluble in water. In the center of the stem is a cavity surrounded by a core that passes into the wood. At industrial reception of flax trusts of a stalk of flax for the purpose of isolation from them fibers are subjected to biological wetting. The uniform and intense moisture of the straw creates the necessary conditions for the life of microorganisms that break down pectin and destroy the tissues of the stem. Experimental studies of the effect of temperature on the rate of wetting of a single straw have shown that the intensity of wetting flax straw with increasing temperature increases especially sharply at temperatures above 60 °C. The process of capillary impregnation of flax straw, which underwent hydrothermal treatment, was also investigated. It is shown that the use of O П -10 solution for pre-hydrothermal treatment further increases the rate of impregnation of the sample. The greatest influence of hydrothermal treatment is observed at the concentration of the solution 0.03 g/l. Key words: linen trust. internal mass transfer, capillary impregnation, hydrothermal treatment

Flax (Linum usitatissimum L.) Fibers for Composite Reinforcement: Exploring the Link Between Plant Growth, Cell Walls Development, and Fiber Properties.

Due to the combination of high mechanical performances and plant-based origin, flax fibers are interesting reinforcement for environmentally friendly composite materials. An increasing amount of research articles and reviews focuses on the processing and properties of flax-based products, without taking into account the original key role of flax fibers, namely, reinforcement elements of the flax stem (Linum usitatissimum L.). The ontogeny of the plant, scattering of fiber properties along the plant, or the plant growth conditions are rarely considered. Conversely, exploring the development of flax fibers and parameters influencing the plant mechanical properties (at the whole plant or fiber scale) could be an interesting way to control and/or optimize fiber performances, and to a greater extent, flax fiber-based products. The first part of the present review synthesized the general knowledge about the growth stages of flax plants and the internal organization of the stem biological tissues. Additionally, key findings regarding the development of its fibers, from elongation to thickening, are reviewed to offer a piece of explanation of the uncommon morphological properties of flax fibers. Then, the slenderness of flax is illustrated by comparison of data given in scientific research on herbaceous plants and woody ones. In the second section, a state of the art of the varietal selection of several main industrial crops is given. This section includes the different selection criteria as well as an overview of their impact on plant characteristics. A particular interest is given to the lodging resistance and the understanding of this undesired phenomenon. The third section reviews the influence of the cultural conditions, including seedling rate and its relation with the wind in a plant canopy, as well as the impact of main tropisms (namely, thigmotropism, seismotropism, and gravitropism) on the stem and fiber characteristics. This section illustrates the mechanisms of plant adaptation, and how the environment can modify the plant biomechanical properties. Finally, this review asks botanists, breeders, and farmers’ knowledge toward the selection of potential flax varieties dedicated to composite applications, through optimized fiber performances. All along the paper, both fibers morphology and mechanical properties are discussed, in constant link with their use for composite materials reinforcement.

Preparation of FeS/iron oxide composite and flax stem‐based porous carbon and its Cr(VI) removal ability

Using flax stem and ferrous sulfate, a composite porous carbon material was prepared by means of high‐temperature roasting and a one‐step process in a muffle furnace. The samples were characterized using X‐Ray diffraction (XRD) and Scanning electron microscopy (SEM), and the effects of ferrous sulfate concentration, carbonization temperature, and pH values of Cr(VI) aqueous solution on the removal performance of Cr(VI) were studied. XRD and SEM analysis showed that the prepared samples were amorphous porous carbon loaded with FeS/Fe2O3/Fe3O4. High FeSO4 impregnation concentration, high carbonization temperature, and a low pH value of Cr(VI) aqueous solution were beneficial for Cr(VI) removal. When pH = 2, the amount of Cr(VI) removal was 99.93 mg/g by the sample obtained from 1 g flax powder impregnated in 4.5 mmol FeSO4/40 mL H2O solution and calcined for 2 hr at 800°C.

Calculation of the Friction Coefficients of Flax Stems according to their Roughness Characteristics

When harvesting flax, its stems get into contact with the working elements of flax harvesting machines. The authors have found that the diversity of materials used to manufacture the working elements made it necessary to calculate the friction coefficients in the interaction between the stems and these materials, since it is not always possible to do this experimentally. They confirmed the possibility of calculating the friction coefficients in the butt, middle and apical parts of the stem. Research purpose Calculation of the friction coefficients of flax stems according to the given microgeometry characteristics of their surface. Materials and methods The studies were carried out on a standard device, a profile meter-and-recorder made by the Kalibr plant, make 201. Common (fibre) flax of the Mogilevskiy 2 variety at the stage of brown ripeness, at a humidity - 43.79 percent, with total length of stems – 78, 9 cm and a flax straw yield of 3.575 tons per hectare were chosen for the experiments. The flax crop was harvested by hand on the experimental field during the harvesting period. During the preparation of experimental samples, the flax stem was divided into three parts - butt, middle and apical. Each of the stem parts was divided into two halves along the axis, then one of the halves was unrolled and pasted on a solid base (steel plate). Profile diagrams of flax stems parts of were processed with conventional methods. Results and discussion The authors have obtained the friction coefficients of the stems of different humidity as they moved along the steel surface. It has been established that the calculated values of the friction coefficients are slightly higher than those obtained as a result of experiments. (Conclusions) It has been established that as the humidity of flax stems increases, the molecular component of the friction coefficient increases too. It has been determined that when the moisture content of the stems is 20-45 percent, the friction coefficient values range from 0.38 to 0.98 percent.

Intrusive Growth of Phloem Fibers in Flax Stem: Integrated Analysis of miRNA and mRNA Expression Profiles.

Phloem fibers are important elements of plant architecture and the target product of many fiber crops. A key stage in fiber development is intrusive elongation, the mechanisms of which are largely unknown. Integrated analysis of miRNA and mRNA expression profiles in intrusivelygrowing fibers obtained by laser microdissection from flax (Linum usitatissimum L.) stem revealed all 124 known flax miRNA from 23 gene families and the potential targets of differentially expressed miRNAs. A comparison of the expression between phloem fibers at different developmental stages, and parenchyma and xylem tissues demonstrated that members of miR159, miR166, miR167, miR319, miR396 families were down-regulated in intrusively growing fibers. Some putative target genes of these miRNA families, such as those putatively encoding growth-regulating factors, an argonaute family protein, and a homeobox-leucine zipper family protein were up-regulated in elongating fibers. miR160, miR169, miR390, and miR394 showed increased expression. Changes in the expression levels of miRNAs and their target genes did not match expectations for the majority of predicted target genes. Taken together, poorly understood intrusive fiber elongation, the key process of phloem fiber development, was characterized from a miRNA-target point of view, giving new insights into its regulation.

Compressive strength of flax fibre bundles within the stem and comparison with unidirectional flax/epoxy composites

Flax (Linum usitatissimum L.) fibres are commonly used as reinforcement of composite materials. Nevertheless, literature shows that the compressive strength of flax-based composites is rather modest compared with materials reinforced by synthetic fibres. The present article investigates the compressive strength of flax fibre bundles both within the stems and in unidirectional (UD) composites. In this way, an optimised arrangement of fibre bundles inside the plant is assumed. Damage mechanisms are found to be similar in the stem and within flax-based UD materials, namely by buckling of fibre bundles, a typical failure mechanism of UD composites. Inside the stems, this phenomenon is highlighted by nanotomography, which underlines the key role of the woody core in the buckling resistance of the plant. For UD, failure can also be studied by scanning electron microscopy (SEM). The same ranges of average compressive strength values are estimated for flax fibre bundles, being 206 MPa within the stem and 242 MPa within UD composites. Finally, this study highlights that, if a flax stem is an optimised natural structure, the compressive strength of flax fibre bundles seems to be a limiting factor for structural applications of flax-based composite materials.

Flax rhamnogalacturonan lyases: phylogeny, differential expression and modeling of protein structure.

Rhamnogalacturonan lyases (RGLs; EC 4.2.2.23) degrade the rhamnogalacturonan I (RG-I) backbone of pectins present in the plant cell wall. These enzymes belong to polysaccharide lyase family 4, members of which are mainly from plants and plant pathogens. RGLs are investigated, as a rule, as pathogen 'weapons' for plant cell wall degradation and subsequent infection. Despite the presence of genes annotated as RGLs in plant genomes and the presence of substrates for enzyme activity in plant cells, evidence supporting the involvement of this enzyme in certain processes is limited. The differential expression of some RGL genes in flax (Linum usitatissimum L.) tissues, revealed in our previous work, prompted us to carry out a total revision (phylogenetic analysis, analysis of expression and protein structure modeling) of all the sequences of flax predicted as coding for RGLs. Comparison of the expressions of LusRGL in various tissues of flax stem revealed that LusRGLs belong to distinct phylogenetic clades, which correspond to two co-expression groups. One of these groups comprised LusRGL6-A and LusRGL6-B genes and was specifically upregulated in flax fibers during deposition of the tertiary cell wall, which has complex RG-I as a key noncellulosic component. The results of homology modeling and docking demonstrated that the topology of the LusRGL6-A catalytic site allowed binding to the RG-I ligand. These findings lead us to suggest the presence of RGL activity in planta and the involvement of special isoforms of RGLs in the modification of RG-I of the tertiary cell wall in plant fibers.

Assessment of agronomic parameters and gene expression profiling of flax (Linum usitatissimum L.) upon treatment with brassinosteroid and its biosynthetic inhibitor

Phytohormones are key regulators of plant growth and development. The plant hormone brassinosteroid (BR) is known to modulate many plant physiological processes via unknown molecular mechanisms. Here, BR and its biosynthetic inhibitor brassinazole (Brz) were studied in flax (Linum usitatissimum L.). Agronomic parameters were measured after spraying various concentrations of BR and Brz onto leaves during rapid growth and budding stages. Using Solexa/Illumina digital gene expression methodology to generate gene expression profiles, a total number of 3163 differentially expressed genes (DEGs) were identified in flax stem tissues treated with BR or Brz for 12 h during the budding stage. A stronger positive effect was exerted on plant agronomic parameters by Brz than BR, with 466, 2135, and 562 DEGs identified from pairwise comparisons of BR vs control check (CK), Brz vs CK, and Brz vs BR, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis assigned 817 DEGs to 237 biological pathways. DEGs related to cellulose and lignin biosynthesis, flax cell development, transcription factors, and phytohormones were up-regulated upon Brz treatment compared with CK. These results deepen the understanding of molecular mechanisms of plant hormone responses in flax, and provide new insights toward improving fiber yield and quality for flax.

Transcriptome Analysis of Intrusively Growing Flax Fibers Isolated by Laser Microdissection

The intrusive growth, a type of plant cell elongation occurring in the depths of plant tissues, is characterized by the invasion of a growing cell between its neighbours due to a higher rate of elongation. In order to reveal the largely unknown molecular mechanisms of intrusive growth, we isolated primary flax phloem fibers specifically at the stage of intrusive growth by laser microdissection. The comparison of the RNA-Seq data from several flax stem parts enabled the characterization of those processes occurring specifically during the fiber intrusive elongation. The revealed molecular players are summarized as those involved in the supply of assimilates and support of turgor pressure, cell wall enlargement and modification, regulation by transcription factors and hormones, and responses to abiotic stress factors. The data obtained in this study provide a solid basis for developing approaches to manipulate fiber intrusive elongation, which is of importance both for plant biology and the yield of fiber crops.

Flax stems: from a specific architecture to an instructive model for bioinspired composite structures

The present paper proposes to carefully study and describe the reinforcement mechanisms within a flax stem, which is an exceptional natural model of composite structure. Thanks to accurate microscopic investigations, with both optical and SEM method, we finely depicted the flax stem architecture, which can be view as a composite structure with an outer protection, a unidirectional ply on the periphery and a porous core; each component has a specific function, such as mechanical reinforcement for the unidirectional ply and the porous core. The significant mechanical role of fibres was underlined, as well as their local organisation in cohesive bundles, obtained because of an intrusive growth and evidenced in this work through nanomechanical AFM measurement and 3D reconstruction. Following a biomimetic approach, these data provide a source of inspiration for the composite materials of tomorrow.

BLISS: Shining a light on lignification in plants

ABSTRACTLignin is a polyphenolic polymer of the plant cell wall formed by the oxidative polymerization of 3 main monomers called monolignols that give rise to the lignin H-, G- and S-units. Together with cellulose and hemicelluloses, lignin is a major component of plant biomass that is widely exploited by humans in numerous industrial processes. Despite recent advances in our understanding of monolignol biosynthesis, our current understanding of the spatio-temporal regulation of their transport and polymerization is more limited. In a recent publication, we have reported the development of an original Bioorthogonal Labeling Imaging Sequential Strategy (BLISS) that allows us to visualize the simultaneous incorporation dynamics of H and G monolignol reporters into lignifying cell walls of the flax stem.11 Here, we extend the application of this strategy to other plant organs such as roots and rapidly discuss some of the contributions and perspectives of this new technique for improving our understanding of the lignification process in plants.

Analysis of public RNA-seq data in studies of flax fiber biogenesis

Abstract In this work we used publicly available raw RNA-seq data to elucidate mechanisms of flax fiber biogenesis by measuring expression of cell-wall related genes (cellulose synthase, cellulose synthase-like and chitinase-like genes) in stem of flax (Linum usitatissimum cv. Bethune). Using public RNA-sequence data we have quantified and characterised the expression of the specific cell-wall genes in the top, middle and bottom parts of the Bethune flax stem. The most prominent findings are: Secondary cell-wall cellulose synthase (CesA) genes are expressed differentially in phloem and xylem in all parts of Bethune stem, in contrast with primary cell-wall cellulose synthase genes. Total expression level of cellulose synthase-like (Csl) genes is tissue invariant (although, CslG and CslE are differentially expressed) and smaller than the total expression of cellulose synthase genes. The CslD2D3 subgroup dominates total expression of CslD genes in both xylem and phloem. Expression levels of all expressed chitinase-like (Ctl) genes are tissue dependent in all parts of stem. Total expression level of chitinase-like genes is much higher than expression of cellulose synthase and cellulose synthase-like genes in both tissues.

Digital gene expression profiling of flax (Linum usitatissimum L.) stem peel identifies genes enriched in fiber-bearing phloem tissue

To better understand the molecular mechanisms and gene expression characteristics associated with development of bast fiber cell within flax stem phloem, the gene expression profiling of flax stem peels and leaves were screened, using Illumina's Digital Gene Expression (DGE) analysis. Four DGE libraries (2 for stem peel and 2 for leaf), ranging from 6.7 to 9.2 million clean reads were obtained, which produced 7.0 million and 6.8 million mapped reads for flax stem peel and leave, respectively. By differential gene expression analysis, a total of 975 genes, of which 708 (73%) genes have protein-coding annotation, were identified as phloem enriched genes putatively involved in the processes of polysaccharide and cell wall metabolism. Differential expression genes (DEGs) was validated using quantitative RT-PCR, the expression pattern of all nine genes determined by qRT-PCR fitted in well with that obtained by sequencing analysis. Cluster and Gene Ontology (GO) analysis revealed that a large number of genes related to metabolic process, catalytic activity and binding category were expressed predominantly in the stem peels. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of the phloem enriched genes suggested approximately 111 biological pathways. The large number of genes and pathways produced from DGE sequencing will expand our understanding of the complex molecular and cellular events in flax bast fiber development and provide a foundation for future studies on fiber development in other bast fiber crops.

Analysis of Linseed Production with Use of Flax Puller and Combine Harvester for its Harvest

The cultivation of linseed is an alternative to the production of flax stem, which is globally on the decline. The alternative method to the traditional harvest using the flax puller is increasing use of combine harvester. By this method the harvest efficiency will be increased, which represents a significant step to an improvement of economy of cultivation. Depending on the variety, the value of specific energy consumption was determined from (0.43 MJ/kg) up to (0.63 MJ/kg) if we use flax puller and from (0.58 MJ/kg) up to (0.86 MJ/kg) if it is used a combine harvester. Levelized costs for seed production in case of soil cultivaton with tillage rangein wide interval (9,714 CZK/t – 17,308 CZK/t) depending on yield of a variety and used machinery.

Transcriptome portrait of cellulose-enriched flax fibres at advanced stage of specialization.

Functional specialization of cells is among the most fundamental processes of higher organism ontogenesis. The major obstacle to studying this phenomenon in plants is the difficulty of isolating certain types of cells at defined stages of in planta development for in-depth analysis. A rare opportunity is given by the developed model system of flax (Linum usitatissimum L.) phloem fibres that can be purified from the surrounding tissues at the stage of the tertiary cell wall deposition. The performed comparison of the whole transcriptome profile in isolated fibres and other portions of the flax stem, together with fibre metabolism characterization, helped to elucidate the general picture of the advanced stage of plant cell specialization and to reveal novel participants potentially involved in fibre metabolism regulation and cell wall formation. Down-regulation of all genes encoding proteins involved in xylan and lignin synthesis and up-regulation of genes for the specific set of transcription factors transcribed during tertiary cell wall formation were revealed. The increased abundance of transcripts for several glycosyltransferases indicated the enzymes that may be involved in synthesis of fibre-specific version of rhamnogalacturonan I.

Impact of the seeding rate on flax stem stability and the mechanical properties of elementary fibres

Cultivation of flax fibres (Linum usitatissimun) for composite reinforcement must provide fibres with good mechanical properties, but also a high fibre yield and lodging stability in order to ensure a stable and satisfactory income for the farmer. This work proposes a study of the impact of the seeding rate on these key parameters. We studied the Aramis variety with 4 different seeding rates (1200, 1500, 1800 and 2500 seeds/m2). The results indicate the significant impact of the seeding rate on the stem’s morphological parameters; its increase induces a progressive decrease of the scutched fibre length and of the stem diameter. At the same time, the higher seeding rates obtained improved the scutched fibre’s yield (+11% between 1200 and 2500 seeds/m2) but, conversely, induced a drop in the elementary fibre’s tensile properties and in the flax stem’s lodging stability, mainly due to the large decrease in the stem’s diameter. This work shows that a compromise must be found to optimize the fibre yield, the mechanical performance and the plant’s stability; it underlines the relevance of using a conventional seeding rate, close to 1800 seeds/m2.

Electro-osmotic dewatering of high moisture flax stems

Retted flax stems contained high amounts of water from the pre-soaking and retting processes. Electro-osmotic dewatering was investigated as a pre-drying process for high-moisture flax stems using a bench electro-osmotic roller press. The various parameters affecting electroosmotic dewatering were cylinder pressure (1000 kPa–3000 kPa), applied voltage (12 V–36 V) and pre-soaking time of the flax stem (12 h–36 h). An experiment was designed using central composite design. From the experiments, a maximum of 38.34% of the total water contained in the stem was removed using 12 h soaking; 1000 kPa cylinder pressure and 36 V applied voltage during the electro-osmotic treatment. For a given soaking time, at 36 V with 3000 kPa cylinder pressure the maximum water removal occurred. The electro-osmotic permeability of the stems at various conditions was studied. In all the treatments, electro-osmotic permeability ranged between 3.32 × 10−5 m2 V−1 s−1 and 1.22 × 10−4 m2 V−1 s−1. Electro-osmotic permeability was found to increase with increasing water removal and decreased with increasing applied voltage.

COMPARATIVE ANALYSIS OF YIELD AND ANATOMICAL MANIFESTATIONS OF SIX FLAX GENOTYPES

two field experiments were conducted at Giza Agric. Res. Station Farm, Agric. Res. Center during the two successive seasons 2012/2013 and 2013/2014. The main objective of this study was to evaluate six flax genotypes for yield and its components, study also anatomical manifestation in the flax main stems at two regions (the middle and at the top of technical stem length) and the transverse sections in seeds. The obtained results can be summarize as follow: The flax variety Giza 10 achieved highest estimates in total plant height, technical stem length , upper branching zone length , straw yield/plant as well as per fad., fiber yield for either per plant or fad., fiber percentage , fiber length and fiber fineness. While, Sakha 3 ranked second in most economic straw traits, the two flax strains i.e., S.402/2 and S.22 were the latest in this case. The strain 22 occupied the first position and surpassed all the five genotypes in no. of capsules/plant , capsules set % , no. of seeds/plant , seed oil percentage , seed yield/fad. and oil yield/fad. The flax variety Giza 8 ranked second in most of seed characters , but the fewest one was Giza 10. Correlation coefficient (r) values were highly significant and positive between total plant height and each of technical stem length, straw yield/plant, fiber yield/plant, fiber percentage and fiber length. While r values were only positively significant with no. of basal branches, fiber fineness and seed yield/plant. Relation between no. of capsules/plant and each of capsules set % and seed yield/plant were highly significant and positive, but it was only significantly positive with no. of seeds/plant and seed oil percentage. Giza 10 variety achieved maximum fiber area/cross section and fiber index estimates (fiber per plant in volume) at either the middle or the top region of flax stem, while S.22 was the lowest in this respect. The majority of different tissues in the transverse section were greater in middle region of stems than in the top of technical length section, except with the cortex area for Sakha 1, Sakha 3 and Giza 10 which took the opposite direction. The flax strain 22 seeds performed highest cotyledons area % per the corresponding total cross section area, the descending arrangement in this case was Giza 8, Sakha 1, S.402/2 , Giza 10 and Sakha 3.

Effects of nitrogen on oilseed flax stem lignin and relative enzyme and lodging resistance

To understand the effects and physiological mechanism of nitrogen regulating lodging resistance,a field experiment was conducted using hybrid oilseed flax Longya 1 in 2012 and 2013. Under 3 nitrogen levels 0,112. 5 and 225 kg /hm2,the investigated traits were lignin contents,relative enzyme activities,snapping resistance,lodging index and actual lodging percentage. Correlation analysis showed that the lignin content of oil flax stem had a positive correlation with PAL,TAL,CAD,4CL,POD activities and snapping resistance,but had a negative correlation with lodging index and actual lodging percentage. Feasible nitrogen fertilizer increased the lignin content,related enzyme activities and lodging resistance. The recommened nitrogen rate for oilseed flax was 112. 5kg /hm2.