Evidence and quantitative evaluation of tensile maturation strain in flax phloem through longitudinal splitting

The stems of flax (Linum usitatissimum L. cv. ‘Mogilevsky’) contain many gelatinous fibers in their phloem. These fibers are important for the mechanical stability of the plant as well as for industrial applications. Gelatinous fibers are known to have a motor function in the xylem of trees and in many plant organs. This function arises from the so-called maturation strain, i.e., the tendency of the gelatinous layer to shrink during fiber maturation, resulting in a state of residual tensile stress. However, the occurrence of tensile maturation strain in flax phloem fibers remains to be demonstrated, and its magnitude has never been evaluated. Here we present a novel method to highlight and quantify this strain. The method consists in splitting a stem segment longitudinally, and measuring the curvature of the half segments through their opening distance. By using a mechanical model, the maturation strain can be calculated from the curvature, the dimensions of the component tissues, and their elastic properties. The model is validated by the agreement between model predictions and observations. The splitting experiment provides qualitative evidence that flax phloem develops tensile stress during maturation, just as xylem gelatinous fibers do. Calculations enable quantitative estimation of the maturation strain. The magnitude of this strain for the material studied is, on average, –1.5%.

Prognostic of the Using Wood of Erythroxylum myrsinites Mart. Under the Anatomic Prism

The composition of the wood and its elements are considered determinants in the wood properties, standing out the fibers, axial parenchyma, number of vessels and rays. In this context, we aimed to investigate and describe the wood anatomical structure of the Erythroxylum myrsinites Mart. and identify its potential uses in the area of wood technology. From the tree, were removed three wood samples for the confection of anatomical slides, witch 3 × 3 × 3 cm, oriented we plans transversal, longitudinal and tangential longitudinal. For the preparation of histological blades, the method of Burger and Richter was adopted; the anatomical description was based on IAWA Committee recommendations. The species presents vessels numerous, solitary, composing 19% of the volume of wood. Diffuse porosity of polygonal contour and thin walls. Mean vascular elements, axial parenchyma representing 3% of the volume of the wood, in a paratracheal vasicentric arrangement. The rays are numerous, occupying 23% of the volume of the wood, narrow and heterogeneous, consisting of procumbent, square and erect cells. The fibers are libriform, of length medium and thick walls, occupying 55% of the volume of the wood, have spiral thickening and septate fibers, absent tracheids, and gelatinous fibers abundant. The characteristics presented give high flexibility to the stem and branches, and the wood with low specific mass, permeable and resistant to mechanical loads has potential for use in energy generation.

Anatomical and ultrastructural studies on gelatinous fibers in the organs of non-woody xerophytic and hydrophytic species

Gelatinous fibers (G-layer) occur widely in various organs and plant tissues of both primary and secondary origin, but they are best known in tension wood. Here, we describe the occurrence, distribution patterns, and structural features of G-fibers in non-woody species of xerophytes and hydrophytes in Brazilian Cerrado (dry soil) and Chaco (wet or periodically waterlogged soils). G-fibers were present in all of the studied species, but were more abundant and more developed in xerophytes. They were associated with the phloem of leaves and primary stems and with the xylem of three xerophytic species that exhibited incipient secondary growth. The G-layer was non-lignified and characterized by greater thickness, lower density, and loose appearance in relation to the secondary layers. Under a transmission electron microscope, G-fibers displayed two secondary parietal layers (S1 and S2) in Prosopis rubriflora Hassle. (xerophyte), three secondary layers (S1, S2, and S3) in Eriosema campestre Benth. var. campestre (xerophyte), and a single secondary layer (S1) in Ludwigia leptocarpa Nutt. (hydrophyte). In P. rubriflora, mature G-fibers exhibited a loose-appearing electron-lucent region (transition zone) between G- and S-layers (secondary layers). In addition to mechanical support, this study suggests the involvement of G-fibers in water storage.

Localization of xyloglucan epitopes in the gelatinous layer of developing and mature gelatinous fibers of European aspen (Populus tremula L.) tension wood

There is controversy concerning the presence of xyloglucans in gelatinous (G) layers of Populus spp. tension wood, particularly in mature G-fibers. Transmission electron microscopy (TEM) immunogold localization combined with LM15 antibody (recognizes XXXG-motif of xyloglucans, heptasaccharide) was used to investigate the distribution of xyloglucan epitopes in both transverse and radial sections of P. tremula tension wood. Results provided clear evidence for the presence of xyloglucans in both mature and developing G-layers. Developmental decrease of LM15 epitope localization in G-layers was also detected during G-fiber maturation. High magnification TEM observations showed specific localization of LM15 epitopes on newly synthesized cellulose macrofibrils present in the innermost layer of developing G-layers adjacent to the cell lumen, suggesting linkage between xyloglucans and cellulose macrofibrils. Possible mechanisms were discussed for developmental changes of xyloglucan with respect to the different results reported in the literature.

Wood anatomy and growth ring boundaries of Copaifera lucens (Fabaceae)

ABSTRACTThe wood anatomy of Copaifera lucens Dwyer was studied with an emphasis on its growth ring boundaries. Growth rings are visible to the naked eye and demarcated by marginal parenchyma bands and, sometimes, by thick-walled fibers in the latewood. Secretory canals are associated with marginal parenchyma bands, but not all marginal parenchyma bands are associated with canals. Paratracheal parenchyma is vasicentric to lozenge-aliform. Rays are 1–4-seriate, heterocellular and non-storied. Vessels are visible to the naked eye, diffuse, predominantly solitary, some in multiples, sometimes filled with gums. Crystals present. Wood anatomical characteristics of C. lucens are in agreement with those previously reported for other species of Copaifera. In addition to what had already been described for C. lucens, we observed gelatinous fibers, and some bifurcate fibers, and extremely rare clustered vessels. The growth ring boundaries are well-defined in mature wood but less distinctive near the pith. There are also partial and confluent (wedging) rings, which are difficult to classify by anatomy only, but which represent false rings and complicate tree-ring analysis in this species.

Leaf morphoanatomy of the medicinal Maytenus imbricata (Celastraceae): an ecological approach

<p><em>Background</em>. The leaves of many species of <em>Maytenus</em> are used to prepare herbal drugs to treat stomach ulcers.</p><p><em>Questions.</em> In order to define key anatomical characters for the unambiguous species identification, the present study aimed to describe the leaf morphoanatomy of <em>M. imbricata.</em></p><p><em>Species study</em>. <em>Maytenus imbricata</em> Mart. ex Reissek (Celastraceae)</p><p><em>Study site and dates.</em> Collected in an area of ‘campo rupestre’ - one of the Brazilian Savannah vegetation (20º22’11.02”S, 43º30’22.81”W) in August 2015.</p><p><em>Methods</em>. The plant material was processed according to commonly used techniques in plant anatomy studies.</p><p><em>Results. </em>The major anatomical characters for several species of <em>Maytenus</em> identification also present in <em>M. imbricata</em> are marginal teeth, conspicuous epicuticular wax, ciclocytic stomata, thick external periclinal wall with large pits on epidermal cells and vascular system with a closed loop shape in cross-section. Strips on the anticlinal walls on epidermal cells and conspicuous gelatinous fibers sheath are diagnostic for <em>M. imbricata</em>.</p><p><em>Conclusions.</em> Strips on the anticlinal wall of the epidermal cell are reported for the first time for the genus. These xeromorphic traits help the species to survive in arid environments and may contribute to quality control of the raw material used in the production of herbal medicines.</p>

Anatomía foliar y del pecíolo de especies del género Rhus s. str. (Anacardiaceae)

Foliar and petiole anatomy of 33 species of Rhus s. str. is described with the main objective of evaluating anatomical traits to support its infrageneric classification. The results support the existing Rhus s. str. infrageneric classification. The subgenus Rhus, with a vascular system type I and more than ten layers of collenchyma and wide pith in the petiole may be readily separated from subgenus Lobadium. In turn, section Terebinthifolia shows two to four vessel elements, collenchymatic sheath surrounding the vascular bundles and gelatinous fibers, while section Styphonia presents a thick cuticle (6 µm), papillose epidermal cells, two layers of palisade parenchyma and sclerenchyma in xylem and phloem. The occurrence of sclerenchyma in section Styphonia is correlated with the persistent character of its leaves. Some of the foliar traits mentioned are undoubtedly related with the radiation events of Rhus s. str. that took place in Mexico.