Showing papers in "Iawa Journal in 2016"

Intervessel pit membrane thickness as a key determinant of embolism resistance in angiosperm xylem

Abstract: Pit membranes in bordered pits between neighbouring vessels play a major role in the entry of air-water menisci from an embolised vessel into a water-filled vessel (i.e., air-seeding). Here, we investigate intervessel pit membrane thickness (TPM) and embolism resistance (P50, i.e., the water potential corresponding to 50% loss of hydraulic conductivity) across a broad range of woody angiosperm species. Data on TPM and double intervessel wall thickness (TVW) were compiled based on electron and light microscopy. Fresh material that was directly fixated for transmission electron microscopy (TEM) was investigated for 71 species, while non-fresh samples were frozen, stored in alcohol, or air dried prior to TEM preparation for an additional 60 species. TPM and P50 were based on novel observations and literature. A strong correlation between TPM and P50 was found for measurements based on freshly fixated material (r = 0.78, P >0.01, n = 37), and between TPM and TVW (r = 0.79, P >0.01, n = 59), while a slightly weaker relationship occurred between TVW and P50 (r = 0.40, P >0.01, n = 34). However, non-fresh samples showed no correlation between TPM and P50, and between TPM and TVW. Intervessel pit membranes in non-fresh samples were c.28% thinner and more electron dense than fresh samples. Our findings demonstrate that TPM measured on freshly fixated material provides one of the strongest wood anatomical correlates of droughtinduced embolism resistance in angiosperms. Assuming that cellulose microfibrils show an equal spatial density, TPM is suggested to affect the length and the shape of intervessel pit membrane pores, but not the actual pore size. Moreover, the shrinking effect observed for TPM after dehydration and frost is associated with an increase in microfibril density and porosity, which may provide a functional explanation for embolism fatigue.

Tyloses and gums: a review of structure, function and occurrence of vessel occlusions

Abstract: Vessel occlusion through tyloses or gums is a natural phenomenon occurring with aging and heartwood formation, and in sapwood in response to vessel embolism. These types of vessel occlusion play a crucial role to limit the spread of pathogens and wood decay organisms, also as part of compartmentalization after wounding. In the sapwood, they can be considered to be an effective stress response.Here we review the literature on tyloses and gums in hardwoods, starting with the detailed 19th century account on tyloses by Hermine von Reichenbach. The structural diversity of tyloses (from thin-walled to sclerotic) and gum deposits is highlighted and illustrated. Our understanding of the development of vessel occlusions through vessel contact cells of the ray and axial parenchyma has greatly increased over the last decades, also thanks to ultrastructural and immunocytological studies. We critically discuss the postulated relationships between vessel-to-ray parenchyma pit size and vessel size and the incidence of either tyloses or gums and review the occurrence of these types of vessel occlusions in extant and fossil dicots. All factors identified in the literature as stimuli for vessel occlusion probably act through vessel embolism as a single direct trigger. Attempts in the literature to relate vessel occlusion with mechanisms of vessel refilling and embolism repair are controversial and invite more experimental research.

Intra-annual density fluctuations in tree rings: how, when, where, and why?

Abstract: Intra-annual density fluctuations (IADFs) in tree rings are generally considered structural anomalies caused by deviations from the “normal course” of xylogenesis during the growing season. This definition is based on the bias that, under “normal conditions”, cambial activity stops once a year. Each tree ring can thus be dated to one calendar year, which is one of the principles of dendrochronology. The formation of IADFs can be triggered directly by environmental changes, especially in precipitation and temperature, that affect cambial activity and cell differentiation. It can also be the result of limited photosynthesis, due to defoliation induced by biotic or abiotic constraints.Often indicated with alternative terms, IADFs were first described in the 1930s, and recently reported for many trees and shrubs from different ecosystems throughout the world, particularly for Mediterranean species. Different types of IADFs have been detected; their formation and structural properties depend on many factors including tree genotype, age, size, rooting depth, habitat, soil, climate, photosynthetic activity, and allocation strategies. Whether IADFs affect the adaptive capability of plants remains, however, unclear.We provide an overview of the main anatomical features of IADFs and their occurrence in tree rings from various environments and climatic regimes. We propose a simplified way of classifying them and discuss the hypotheses about their functional role and the factors triggering their formation. To understand the ecological role of IADFs better, we recommend a multidisciplinary approach, involving wood anatomy, dendroecology, and stable isotopes, which has already been applied for Mediterranean species. We conclude by considering that IADFs appear to be the “rule” rather than “anomalies” in some ecosystems where they help plants cope with fluctuating environmental conditions. Moreover, their anatomical structure represents a valuable proxy of past climatic conditions at a sub-seasonal resolution and may be relevant to adapt hydraulic functioning of living trees to changing climatic conditions.

Wood anatomy and trait-based ecology

Abstract: The largest part of forest biomass consists of wood. A global estimate of carbon stored in lignified tissues rises up to 400 Pg. Given these quantities, there is a growing interest of implementing wood research in diagnoses and evaluations of the carrying capacity of the global ecosystem and its forests. The question arises how disciplines like wood anatomy could respond to the increasing demands of a trait-based ecology, understood as a paradigmatic shift in addressing global changes. Dendrochronology and ecological wood anatomy, traditionally operating within the paradigm of species-based ecology, developed robust methods to address ecological questions. However, sampling strategies and database design will likely be different when wood traits are to be used to study individual tree performance, including responses to stress.Aiming at optimally involving wood research in trait-based ecology, some trait concepts are analysed. The value of the IAWA standard lists of wood anatomical features as starting points for trait databases is recognized. A summary of the functionality of wood is given to inform the trait-research community of basic aspects of tree performance. The time dimension is highlighted, as well as the foundations for understanding bio-hydraulics, bio-mechanics and metabolism of wood and relevant traits.Guidelines are given for sampling strategies and database concepts. Prospects of time axis construction and system integration are discussed, as well as the importance of standardizing for size.

Earlywood vessels in ring-porous trees become functional for water transport after bud burst and before the maturation of the current-year leaves

Abstract: This paper reviews the development of xylem vessels in ring-porous dicots and the corresponding leaf phenology. Also included are our original observations on the time-course of vessel element growth, secondary wall deposition, and end wall perforation in the deciduous hardwood Kalopanax septemlobus. Different patterns of xylem growth and phenology serve different strategies of the species for adaptation to seasonal climates. Trees with ring-porous xylem form wide earlywood vessels (EWV) in spring and narrow latewood vessels in summer. The wide EWV become embolized or blocked with tyloses by the end of the growing season while the narrow vessels may remain functional for many years. The co-occurrence of wide and narrow vessels provides both efficiency and safety of the water transport as well as a potentially longer growing season. It has for a long time been assumed that EWV in ring-porous hardwoods are formed in early spring before bud burst in order to supply sap to growing leaves and shoots.However, the full time-course of development of EWV elements from initiation of growth until maturation for water transport has not been adequately studied until recently. Our observations clarify a crucial relationship between leaf maturation and the maturation of earlywood vessels for sap transport. Accumulated new evidence shows that EWV in branches and upper stem parts develop earlier than EWV lower in the stem. The first EWV elements are fully expanded with differentiated secondary walls by the time of bud burst. In lower stem parts, perforations in vessel end walls are formed after bud burst and before the new leaves have achieved full size. Therefore, the current-year EWV network becomes functional for water transport only by the time when the first new leaves are mature.

Tree-ring features: indicators of extreme event impacts

Abstract: Wood anatomical features may be visible on the microscopic as well as on the macroscopic scale. While the former can often be quantified by detailed wood anatomical analyses, the latter are often treated as qualitative features or as binary variables (present/absent). Macroscopic tree-ring features can be quantified in terms of frequency, intensity, or classified according to their position within a tree ring, like intra-annual density variations (IADFs) in conifers or frost rings in earlywood or latewood. Although some of these tree-ring features, like e.g. missing rings or IADFs are often seen as anomalies, hampering dendrochronologists to perform proper crossdating of tree-ring series, many of these properties are formed under extreme environmental stress or heavy impact, and could mark these extreme events by the manifestation in the wood anatomical structures throughout the lifespan of trees. The described tree-ring features form discrete time-series of extreme events. For example, flood rings may be marked by lunar-shaped earlywood vessels or enlarged latewood vessels in ring-porous oaks. White earlywood rings and light rings indicate reduced cell wall thickness and lignification occurring in very cold years. Frost rings result from cambial cell death during abrupt cooling events in the growing season. Missing rings and IADFs are mainly caused by drought events. Characteristic variations in earlywood vessel size, shape, or number in ring-porous oak species are markers for flood events, defoliation, heat stress, or drought. Traumatic resin ducts may be triggered by a range of biotic or environmental stressors, including wounding, fires or mechanical factors. Reaction wood is indicative of mechanical stress, often related to geomorphic events. In many cases anatomical responses are unspecific and may be caused by different stressors or extreme events. Additionally, the sensitivity of trees to form such features may vary between species, or between life stages within one species. We critically evaluate the indicative value of different wood anatomical tree-ring features for environmental reconstructions.

Ring-porosity and earlywood vessels: a review on extracting environmental information through time

Abstract: Many anatomical features in trees result from their reaction to fluctuating environmental conditions, and some can be measured and dated. Recently, quantitative wood anatomy has been used to build time series, and consequently to study the responses of trees through time. This involves the application of dendrochronological techniques, although some methodological adaptations are necessary when using anatomical variables. Until now, the study of continuous anatomical series has proven to be very promising when applied to the earlywood vessels of ring-porous trees, due to their great physiological relevance.In this paper, we review the main aspects that must be considered when building continuous series of earlywood vessel features of ring-porous trees as compared to ‘classical’ dendrochronology. We first discuss the procedures for building individual series and chronologies, starting with the selection of variables, examining their statistical properties, and assessing how crossdating and detrending should be adapted. We also show that time series of earlywood vessels usually exhibit a low common signal, but in contrast are strongly related to climate, and often reveal responses not recorded by the classical dendrochronological variables.In addition, we deal with the optimization of environmental signals, by first evaluating multiple potential variables to be used, and indicate how to reduce their number according to the relations among them. As earlywood variables are basically determined by vessel number or vessel size, we discuss the search for the most appropriate variable to characterize vessel number, as well as the advantage of progressively selecting earlywood vessels attending to their size and position.Finally, we extend the application of these methodologies to diffuse-porous species as compared to ring-porous trees, and show that the climatic signal contained in their anatomical features is also relevant, provided that vessels are carefully selected upon their location within the ring.

Nirs identification of swietenia macrophylla is robust across specimens from 27 countries

Abstract: Big-leaf mahogany is the world’s most valuable widely traded tropical timber species and Near Infrared Spectroscopy (NIRS) has been applied as a tool for discriminating its wood from similar species using multivariate analysis. In this study four look-alike timbers of Swietenia macrophylla (mahogany or big-leaf mahogany), Carapa guianensis (crabwood), Cedrela odorata (cedar or cedro) and Micropholis melinoniana (curupixa) have been successfully discriminated using NIRS and Partial Least Squares for Discriminant Analysis using solid block and milled samples. Species identification models identified 155 samples of S. macrophylla from 27 countries with a correct classification rate higher than 96.8%. For these specimens, the NIRS spectrum variation was more powerful for species identification than for determining provenance of S. macrophylla at the country level.

Tracheid and pit anatomy vary in tandem in a tall sequoiadendron giganteum tree

Abstract: Across land plants there is a general pattern of xylem conduit diameters widening towards the stem base thus reducing the accumulation of hydraulic resistance as plants grow taller.In conifers, xylem conduits consist of cells with closed end-walls and water must flow through bordered pits imbedded in the side walls. As a consequence both cell size, which determines the numbers of walls that the conductive stream of water must cross, as well as the characteristics of the pits themselves, crucially affect total hydraulic resistance. Because both conduit size and pit features influence hydraulic resistance in tandem, we hypothesized that features of both should vary predictably with one another. To test this prediction we sampled a single tall (94.8 m) Sequoiadendron giganteum tree (giant sequoia), collecting wood samples from the most recent annual ring progressively downwards from the tree top to the base. We measured tracheid diameter and length, number of pits per tracheid, and the areas of pit apertures, tori, and margos. Tracheid diameter widened from treetop to base following a power law with an exponent (tracheid diameterstem length slope) of approximately 0.20. A similar scaling exponent was found between tracheid length and distance from tree top. Additionally, pit aperture, torus, and margo areas all increased (again with a power of ~0.20) with distance from tree top, paralleling the observed variation in tracheid diameter and length. Pit density scaled isometrically with tracheid length. Within individual tracheids, total permeable area of pits, measured as the sum of the margo areas, scaled isometrically with lumen area. Given that pores of the margo membrane are believed to increase in parallel with membrane area, from a strictly anatomical perspective, our results support the interpretation that pit resistance remains a relatively constant fraction of total resistance along the hydraulic pathway.

GROWTH-RING DISTINCTNESS and BOUNDARY ANATOMY VARIABILITY in TROPICAL TREES

Abstract: The phenomenon of distinct, absent or indistinct growth rings is a highly variable feature used for wood identification and a wide range of tree-ring studies. Causes for its variability are not yet fully understood. There is also a lack of consensus within the scientific community about how distinct and indistinct tree rings should be defined and classified. We use a selection of 103 Central African rainforest trees to analyse the anatomy of growth-ring boundaries of 103 Central African rainforest species and assessed the influence of the climate, tree organ and leaf shedding behaviour on growth-ring distinctness and anatomy. We observed a high variability of tree-ring boundaries anatomy and distinctness within and among individuals and species. Although, for some semi-deciduous species, higher incidence of distinct growth rings appears to be related with a more pronounced seasonal climate, no general trends are observed for the assembly of studied species. Growth rings are variable within individuals depending on the considered organ: trunks tend to show more distinct rings than branches. Growth-ring distinctness is difficult to implement as a trait to measure tree performance when only based on abrupt changes in fibre size and cell wall thickness. From the potential growth-ring markers identified in the IAWA list of hardwood features, those applying to vessel and parenchyma density and distended rays appear to be more useful in tropical trees than abruptly flattened latewood fibres or abrupt changes in vessel diameter.

The effects of drought on wood formation in fagus sylvatica during two contrasting years

Abstract: We studied the effect of local weather conditions on intra-annual wood formation dynamics and wood structure of European beech (Fagus sylvatica L.) from a temperate location in the Czech Republic in two consecutive years, 2010 and 2011, characterized by different amounts of precipitation. Microcores were taken at weekly intervals and transverse sections of cambial and xylem tissue were prepared for light microscopic observation. Air temperature and soil moisture content were measured daily at the research plot. Tree-ring formation patterns and vessel features showed different responses to climatic factors in the two years. In 2010, the onset of cambial cell production occurred almost 10 days later than in 2011, when a considerably reduced amount of rainfall was already observed in the winter and spring months, as shown in Standardized Precipitation Index (SPI) values. Lack of precipitation in 2011 caused premature cessation of cambial cell division and markedly narrower annual xylem increments. Vessel density and water conductive area were higher in 2011 than in 2010. Average vessel size in general did not change. In response to local weather conditions, beech controls its hydraulic conductivity mainly by changing the number of vessels and tree growth rate, followed by vessel size. The lower sensitivity of vessel diameter to hydrological alterations confirms previous studies by other authors.

Missing and dark rings associated with drought in pinus halepensis

Abstract: The responses of the vascular cambium and tracheid differentiation to extreme drought in Aleppo pine (Pinus halepensis Mill.) were investigated. The research focused on the drought year of 2005, in the primary study area at Maigmo (MAI) in southeastern Spain, with comparisons in Jarafuel (JAL) and Guardamar (GUA). The climate in this region is typically warm and dry with hot summers. Wood formation throughout the 2005 growing season was studied in transverse microtome sections and integrated with a retrospective dendrochronological analysis of crossdated increment cores collected in 2009. For most anatomical sections collected throughout the growing season at MAI, the vascular cambium appeared to be dormant as indicated by the low number of cells per radial file. Occasionally, immature xylem derivatives were observed during the growing season but without production of an annual ring. In increment cores collected at MAI, the 2005 position in the annual ring series contained either a narrow ring of both earlywood and latewood (47% of samples), a narrow ring of apparent latewood with no earlywood (13%), or a missing ring (50%). We introduce the term “dark ring” to refer to those annual rings of apparent latewood with no earlywood. For trees at JAL, the 2005 ring had below-average width and contained both earlywood and latewood. At GUA, the trees produced the widest 2005 ring of all three sites and mainly contained an intra-annual density fluctuation (IADF). The IADF was formed after cambial reactivation in the autumn. Although dark rings, IADFs, and especially missing rings complicate dendrochronological analysis, these anatomical features may provide an additional proxy record from which to infer climate variability and change in the past.

Charcoal collections of the world

Abstract: Charcoal reference collections are very important for identifying unknown charcoal specimens in different contexts (palaeoecological, archaeological, environmental and others) and form an integral part of anthracological studies, which can provide crucial information for researchers of different expertise, as wood anatomy, archaeology, palaeobotany, forestry, forensics, etc. A first inventory on charcoal collections maintained by scientific institutions or private individuals around the world revealed 53 charcoal collections in five continents. There is a high concentration of collections and specimens in Europe, reflecting a better established and longer tradition of charcoal identification in temperate and mediterranean regions. However, research seems to be firmly advancing in other parts of the world, especially in the tropics, where important collections are being established. The great increase observed in the number of existing charcoal collections and their geographical spread in the last years attest to their importance, as well as to the vigour of anthracology in its various approaches. The wood anatomical community is called upon to help fill gaps in this first inventory of charcoal collections.

Lack of annual periodicity in cambial production of phloem in trees from mediterranean areas

Abstract: Annual periodicity of cambium production of xylem and phloem cells has rarely been compared in trees from different environments. We compared the structure of cambium and the youngest xylem and phloem increments in four tree species, Fagus sylvatica, Picea abies, Pinus sylvestris and Pinus halepensis, from nine temperate and Mediterranean sites in Slovenia and Spain. In Picea abies, Pinus sylvestris and Fagus sylvatica from temperate locations in Slovenia, xylem and phloem growth ring boundaries could be identified. In Fagus sylvatica growing at two elevations on Moncayo mountain, Spain, phloem increment consisted of only early phloem. In Pinus sylvestris from the same two sites, growth ring boundaries were not as clear as in temperate Slovenian sites. In some cases we could identify phloem growth ring boundaries but in others it was very doubtful, which could be explained by collapse of the outermost early phloem sieve cells. In Pinus halepensis from all sites, we could only distinguish between collapsed and non-collapsed phloem, while phloem rings could not be identified. Widths of the youngest phloem and xylem annual increments could only be compared when phloem increments could be clearly defined, as with Picea abies, Fagus sylvatica and Pinus sylvestris from temperate sites. The visibility of the growth ring boundary in phloem was not related to the width of annual radial growth. The correlation between xylem and phloem ring widths was high, but moderate between the number of dormant cambial cells and xylem ring and phloem ring widths. Based on the structure of the youngest phloem increments, we concluded that there is no typical annual periodicity in cambial production of phloem cells in trees from certain Mediterranean sites. This may be due to continuous yearlong cell production and the absence of true cambium dormancy, at least on the phloem side, under mild winter conditions.

Using idioblasts to group laurinoxylon species: case study from the oligo-miocene of europe

Abstract: Several specimens of Lauraceae fossil wood from the Cenozoic of Greece (southern part of Lesbos), the Czech Republic (Kadaň-Zadni Vrch Hill and Jachymov), and Hungary (Ipolytarnoc) were studied. When considering whether they belonged to the speciose fossil wood genus Laurinoxylon, we reviewed the literature and data from InsideWood on fossil and modern woods. As a result, we propose criteria for excluding a fossil Lauraceae wood from Laurinoxylon and list the species that should be excluded from this genus. The criteria (filters) proposed to exclude a genus from having relationships with Laurinoxylon are: A. Axial parenchyma features: A1. Marginal axial parenchyma, A2. Aliform to aliform-confluent paratracheal parenchyma. B. Ray features: B1. Rays higher than 1 mm, B2. Exclusively homocellular rays, B3. Rays more than 5 cells wide, B4. Rays storied. C. Porosity features: Ring-porous. D. Idioblasts: Absence of idioblasts. Based on the distribution of idioblasts, we recognize four groups in Laurinoxylon (Type 1 - with idioblasts associated only with ray parenchyma cells, Type 2a - with idioblasts associated with both ray and axial parenchyma, Type 2b - with idioblasts associated both with rays and present among the fibres, and Type 3 - with idioblasts associated with ray and axial parenchyma and also among the fibres) and list the extant genera with features of those groups. Such grouping helps with interpreting the relationships of fossil lauraceous woods with extant genera. We discuss the Oligocene–Miocene European species that belong to these Laurinoxylon groups, noting that some warrant reassignment to different genera or even families. Future studies are needed to determine whether new genera should be established to accommodate these species. We propose the new combination Cinnamomoxylon variabile (Prive-Gill & Pelletier) Mantzouka, Karakitsios, Sakala & Wheeler.

Wood anatomy and acoustic properties of selected tropical hardwoods

Abstract: Selected anatomical features and ground tissue composition were studied in four tropical hardwoods (Afzelia sp. [Doussie], Intsia sp. [Merbau], Astronium sp. [Muiracatiara] and Millettia sp. [Wenge]). These woods can be applied in musical instrument production, especially for xylophone bars. The measured density, 1st bending natural frequency and the logarithmic decrement of damping were used to calculate other acoustic properties such as dynamic young modulus of elasticity (Erf ), specific modulus of elasticity (E´/ρ), internal friction (tan δ), and acoustic conversion efficiency (ACE).The correlations between anatomy and acoustic properties were determined. Despite difficulties in specifying general characteristics of hardwoods due to their complicated and variable structure, correlations valid between species were found for specific modulus of elasticity. Specific modulus of elasticity was negatively correlated with ray tissue volume and positively with ray height to width ratio and fiber length. The diversity in ground tissue composition was the main criterion for the species choice and probably should condition diverse correlations of anatomical features found for individual species. It seems that better acoustic properties (higher stiffness, ACE or specific modulus of elasticity) are performed by wood with longer fibers and slender rays, causing minimal deflection of adjoining fibers.

Density and loss on ignition as indicators of the fossilization of silicified wood

Abstract: Measuring density of silicified wood and determining weight loss after 450°C heating provides useful data for interpreting the process of permineralization. These simple gravimetric methods do not replace X-ray diffraction, electron microscopy, polarized light microscopy, Raman spectroscopy, and other specialized techniques for studying fossil wood, but they can be performed rapidly, and require minimal laboratory facilities. Woods mineralized with opal have densities of 1.9–2.1 g/cm3, compared to 2.3–2.6 g/cm3 for wood mineralized with chalcedony or quartz. Weight loss after 450°C heating, commonly described as “loss on ignition” can be used to roughly estimate the % of original organic matter that remains in chalcedony or quartz-mineralized wood, using the density of extant taxa for comparison. For opalized wood, 450°C weight loss mostly represents dehydration of the hydrous silica. Data from specimens from 20 localities reveal two characteristics: 1) silicified woods typically consist either of opal or chalcedony/quartz, not an intermediate mixture of the two silica polymorphs; 2) the percentage of organic matter that remains after petrifaction is usually very small.

Timing of vessel formation in twigs and trunks in relation to porosity and leaf flushing

Abstract: In order to understand the coordination of leaf phenology and functional xylem anatomy, the timing of vessel wall lignification in twigs and stems in relation to leaf appearance was studied in nine species with different porosity patterns. Cylindrical stem cores and twigs were collected from early spring through late summer from deciduous (Quercus serrata, Liquidambar styraciflua, and Acanthopanax sciadophylloides), and evergreen (Castanopsis cuspidata; Cinnamomum camphora, Ilex pedunculosa, Symplocos prunifolia, Quercus glauca and Quercus myrsinifolia) species in a temperate forest. The first-formed twig vessels lignified at the time of leaf appearance or before in all species. The timing of stem vessel lignification in relation to leaf appearance in semi-ringporous deciduous species was overlapping with that of ring-porous deciduous species and diffuse-porous deciduous species. Evergreen species showed a great variation in the timing of stem vessel lignification, relative to leaf flushing. The main conclusions are that 1) Vessel lignification occurs much earlier in twigs than in trunks of the same trees, with hardly any overlap between the two; 2) Deciduous trees do not differ much from evergreen species, but there is a weak tendency for evergreen species to have later vessel differentiation than deciduous species; 3) The timing of vessel formation shows little relation with porosity patterns and overlaps between diffuse-porous and ring-porous species. This suggests a much greater intergradation of timing of vessel formation in species of different porosity pattern in evergreen and deciduous species than recognized in the literature.

Variations in cell wall ultrastructure and chemistry in cell types of earlywood and latewood in english oak (quercus robur)

Abstract: Although there is considerable information on anatomy and gross chemistry of oak wood, little is known on the ultrastructure and chemistry at the individual cell wall level. In particular, differences in ultrastructure and chemistry within the same cell type between earlywood (EW) and latewood (LW) are poorly understood. This study investigated the ultrastructure and chemistry of (vasicentric) tracheids, vessels, (libriform) fibers and axial/ray parenchyma cells of English oak xylem (Quercus robur L.) using light-, fluorescence- and transmission electron microscopy combined with histo/cytochemistry and immunohisto/ cytochemistry. EW tracheids showed several differences from LW tracheids including thinner cell walls, wider middle lamella cell corner (MLcc) regions and lesser amounts of mannan epitopes. Fibers showed thicker cell walls and higher amounts of mannan epitopes than tracheids. EW vessels were rich in guaiacyl (G) lignin with a characteristic non-layered cell wall organization (absence of S1–3 layers), whereas LW vessels were rich in syringyl (S) lignin with a three layered cell wall structure (S1–3 layers). Formation of a highly lignified and wide protective layer (PL) inside axial/ray parenchyma cells was detected only in EW. Distribution of mannan epitopes varied greatly between cell types and between EW and LW, whereas distribution of xylan epitopes was almost identical in all cell types within a growth ring. Together, this study demonstrates that there are great variations in ultrastructure and chemistry of cell walls within a single growth ring of English oak xylem.

Wood anatomy of Cupressus and its relation to geographical distribution

Abstract: The wood anatomy of 14 species of Cupressus was studied to determine whether there is a pattern of wood anatomical diversity between the species from the North and Central American (western) region and the Eurasian (eastern) region. Xanthocyparis vietnamensis and Chamaecyparis nootkatensis (syn. Xanthocyparis nootkatensis) were also studied to compare their wood anatomy, given their recent inclusion by some authors in Cupressus. The arrangement of the axial parenchyma, morphology of the transverse end walls of the axial parenchyma, presence of ray tracheids, typology of the end walls of the ray parenchyma cells and ray height support to some extent the division of Cupressus into two large groups: the American group (western region) and the Eurasian group (eastern region), as proposed in molecular phylogenetic studies. The wood anatomy of Chamaecyparis nootkatensis shares the presence of ray tracheids and the same ray typology with American Cupressus, and has the same ray height as Eurasian Cupressus. In contrast, Xanthocyparis vietnamensis shares the absence of ray tracheids and the same ray typology with Eurasian Cupressus, and has the same ray height as American Cupressus.

Distribution of phenolic compounds, pectins and hemicelluloses in mature pit membranes and its variation between pit types in english oak xylem ( quercus robur )

Abstract: Although there is considerable information on the chemistry of bordered intervessel pit membranes, little is known on the pit membrane chemistry of other pit types in hardwoods. This study investigated distribution of phenolic compounds, pectins and hemicelluloses in different mature pit membranes of English oak xylem using transmission electron microscopy coupled with cytochemistry and immunocytochemistry. Mature bordered intertracheid (vasicentric)- and tracheid-vessel pits showed presence of xyloglucan and heteromannan (hemicelluloses) epitopes across the pit membrane (except for the annulus regions) with differences in amounts of epitopes between earlywood (EW) and latewood (LW). In contrast, pectin epitopes were detected only in the annulus regions of pit membranes. Unlike bordered pits, half-bordered (tracheary-parenchyma pits) and simple (parenchyma pits) pit membranes were rich in pectin epitopes but lacked heteromannan epitopes, indicating difference in pit membrane chemistry between pit types. Distribution of phenolic compounds also differed between pit types and between EW and LW. LW also showed great variations in distribution of phenolic compounds between vessels. Together, this study demonstrates that there are great variations in pit membrane chemistry between pit types and between EW and LW in English oak xylem.

Bark anatomy of Late Permian glossopterid trees from Antarctica

Abstract: The Glossopteridales are an extinct group of seed plants that dominated Gondwanan floras during the Permian. Their remains are found across a wide range of habitats and paleolatitudes, and it is particularly interesting to understand the anatomical characteristics that might have enabled such an extensive distribution. Here, we document for the first time the bark anatomy of high-latitude glossopteridalean trees using peels and thin sections made from a Late Permian trunk from Skaar Ridge, Antarctica. The bark is 3 cm thick. The secondary phloem is composed of sieve cells, axial and ray parenchyma, and fibers arranged in discontinuous unicellular tangential layers. The outer bark is a rhytidome, with numerous alternating layers of periderm and non-conducting secondary phloem showing some proliferation of the axial parenchyma. Successive periderms mostly run parallel to the cambium, with some longitudinal undulation and rare connections between two periderms. A similar anatomy was observed in bark fragments found isolated in the matrix or closely associated with large glossopterid stems or roots. The anatomy of the Skaar Ridge specimens shows that Antarctic Glossopteridales had a relatively thick, probably stringy bark. The retention of a significant amount of insulating dead bark tissue on the trunk likely provided protection of the cambium, conducting secondary phloem, and potential latent buds against biotic and abiotic environmental hazards (fire, frost, scalding, insects, etc.) and may have contributed to the extensive paleolatitudinal distribution of the Glossopteridales during the Permian

Computed Tomography and light microscopy: combining visualisation techniques in the study of mangrove seedling development

Abstract: When seedlings grow into young plants their tissue proportions change over time. Viviparous mangrove seedlings of the Rhizophoraceae are different from other young trees. They consist of a thickened cylinder-shaped hypocotyl that allows the seedlings to float and disperse before establishment. Despite the crucial role in the ecological and biogeographical success of mangroves, not much has been published about the internal development of mangrove seedlings in their early life stages. We used X-ray CT-scanning and light microscopy to investigate the internal development (i) over time and (ii) with hypocotyl height in seedlings of the mangrove species Bruguiera gymnorrhiza and Ceriops tagal. While light microscopy offered cell- and tissue identification in destructive transverse sections, X-ray CT-scanning allowed investigating the internal tissue development of living plants over time in a non-destructive way. Our results indicated that the vascular tissue proportionally increased over time and with hypocotyl height in both species in accordance with the growing importance of this tissue in the developing seedlings. As a result, the cortex, composed of an inner and outer zone, proportionally decreased over time and with height in both species. No clear trends over time and with height could be observed regarding the proportion of the pith tissue. A decrease in average density of all tissues together with height was discerned in both species indicating the seedlings were heavier at their base. The latter suggests a supporting role of the seedling base in tidal and wind action. The combination of CT-scanning and light microscopy offered the advantages of both methods in the developmental study of young mangrove plants, and opens perspectives in the study of internal development of young plants in general.

Stem anatomy of some species of passiflora (passifloraceae)

Abstract: The stem anatomy of Passiflora edulis, P. foetida, P. suberosa, P. subpeltata, and P. vesicaria was studied in samples collected in Durban (KwaZulu-Natal Province, South Africa) and Baroda (Vadodara, Gujarat State, India). Radial stem growth in all the species is realized by a single, bidirectional vascular cambium. However, unequal activity in small segments of the cambial cylinder results in a lobed stem outline in P. foetida var. ellisonii, and a furrowed xylem cylinder in P. edulis f. edulis and P. vesicaria var. vesicaria. In P. subpeltata and P. edulis f. flavicarpa the xylem remains cylindrical in outline. In all the species investigated, secondary xylem is diffuse-porous with growth rings indistinct or absent. In transverse view, vessels are round to oval with different diameter categories, including very narrow fibriform vessels intermixed. In P. edulis f. edulis, stems are lobed due to the unidirectional activity of the cambium in small segments. Rays are mostly both narrow (1–3-seriate) and wide (multiseriate). The latter often become aggregate at some distance from the pith.

Inside the Dogon Masks: The Selection of Woods for Ritual Objects

Abstract: At the foot of the Bandiagara cliffs in Mali lives one of the most studied and yet most mysterious ethnic groups of West Africa, the Dogon. According to their religion, masks have a key role in traditional rites, since they are the link between the earthly and the divine. The production and maintenance of such important tools have precise rules handed down by the Dogon secret society called Awa. Fifteen traditional Dogon masks were studied to ascertain the wood species selected to carve them. The analysis shows the occasional use of marula (Sclerocarya birrea, 3 masks) and African grape (Lannea spec., 2 masks) and a preference for ceiba (Ceiba pentandra, 10 masks), a tree revered as sacred by the Dogon. The results suggest potential implications concerning the use of trees and woods in Dogon tradition.

Incident light microphotography at high depth of focus

Abstract: A new method for stacked microphotography of 3D wood structures is described and illustrated with a practical protocol for visualizing the multiple perforation plates of Goupia glabra as seen in transverse surfaces.