Alan Crivellaro

Universal hydraulics of the flowering plants: vessel diameter scales with stem length across angiosperm lineages, habits and climates

Angiosperm hydraulic performance is crucially affected by the diameters of vessels, the water conducting conduits in the wood. Hydraulic optimality models suggest that vessels should widen predictably from stem tip to base, buffering hydrodynamic resistance accruing as stems, and therefore conductive path, increase in length. Data from 257 species (609 samples) show that vessels widen as predicted with distance from the stem apex across angiosperm orders, habits and habitats. Standardising for stem length, vessels are only slightly wider in warm/moist climates and in lianas, showing that, rather than climate or habit, plant size is by far the main driver of global variation in mean vessel diameter. Terminal twig vessels become wider as plant height increases, while vessel density decreases slightly less than expected tip to base. These patterns lead to testable predictions regarding evolutionary strategies allowing plants to minimise carbon costs per unit leaf area even as height increases.

AXIAL CONDUIT WIDENING IN WOODY SPECIES: A STILL NEGLECTED ANATOMICAL PATTERN

Within a tree the lumen of the xylem conduits varies widely (by at least 1 order of magnitude). Transversally in the stem conduits are smaller close to the pith and larger in the outermost rings. Axially (i.e. from petioles to roots) conduits widen from the stem apex downwards in the same tree ring. This axial variation is proposed as being the most efficient anatomical adjustment for stabilizing hydraulic path-length resistance with the progressive growth in height. The hydrodynamic (i.e. physical) constraint shapes the whole xylem conduits column in a very similar way in different species and environments. Our aim is to provide experimental evidence that the axial conduit widening is an ineluctable feature of the vascular system in plants. If evolution has favoured efficient distribution networks (i.e. total resistance is tree-size independent) the axial conduit widening can be predicted downwards along the stem. Indeed, in order to compensate for the increase in path length with growth in height the conduit size should scale as a power function of tree height with an exponent higher than 0.2. Similarly, this approach could be applied in branches and roots but due to the different lengths of the path roots-leaves the patterns of axial variations of conduit size might slightly deviate from the general widening trend. Finally, we emphasize the importance of sampling standardization with respect to tree height for correctly comparing the anatomical characteristics of different individuals.

Quantitative wood anatomy—practical guidelines

Quantitative wood anatomy analyzes the variability of xylem anatomical features in trees, shrubs, and herbaceous species to address research questions related to plant functioning, growth, and environment. Among the more frequently considered anatomical features are lumen dimensions and wall thickness of conducting cells, fibers, and several ray properties. The structural properties of each xylem anatomical feature are mostly fixed once they are formed, and define to a large extent its functionality, including transport and storage of water, nutrients, sugars, and hormones, and providing mechanical support. The anatomical features can often be localized within an annual growth ring, which allows to establish intra-annual past and present structure-function relationships and its sensitivity to environmental variability. However, there are many methodological challenges to handle when aiming at producing (large) data sets of xylem anatomical data. Here we describe the different steps from wood sample collection to xylem anatomical data, provide guidance and identify pitfalls, and present different image-analysis tools for the quantification of anatomical features, in particular conducting cells. We show that each data production step from sample collection in the field, microslide preparation in the lab, image capturing through an optical microscope and image analysis with specific tools can readily introduce measurement errors between 5 and 30% and more, whereby the magnitude usually increases the smaller the anatomical features. Such measurement errors—if not avoided or corrected—may make it impossible to extract meaningful xylem anatomical data in light of the rather small range of variability in many anatomical features as observed, for example, within time series of individual plants. Following a rigid protocol and quality control as proposed in this paper is thus mandatory to use quantitative data of xylem anatomical features as a powerful source for many research topics.

Comparative axial widening of phloem and xylem conduits in small woody plants

Key messageAlong the stem axis phloem’s sieve elements increase in diameter basally at rates comparable to those of xylem conduits and in agreement with principles of hydraulic optimization.AbstractPlant physiology relies on the efficiency of the two long-distance transport systems of xylem and phloem. Xylem architecture comprises conduits of small dimensions towards the stem apex, where transpiration-induced tensions are the highest along the root-to-leaves hydraulic pathway, and widen basally to minimize the path length resistance to water flow. Instead, information on phloem anatomy and allometry is extremely scarce, although potentially relevant for the efficiency of sugar transportation. We measured the hydraulic diameter (Dh) of both xylem conduits and phloem sieve elements in parallel at different heights along the stem of a small tree of Picea abies, Fraxinus excelsior and Salix eleagnos. Dh increased from the stem apex to base in both xylem and phloem, with a higher scaling exponent (b) of sieve elements than that of tracheids in the conifer (0.19 vs. 0.14) and lower than that of vessels in the angiosperms (0.14–0.22 vs. 0.19–0.40). In addition, sieve elements were larger than tracheids in P. abies and narrower than angiosperms vessels at any height along the stem. In conclusion, axial conduit widening would seem to be a key feature of both xylem and phloem long-distance transport architectures.

Atlas of Wood, Bark and Pith Anatomy of Eastern Mediterranean Trees and Shrubs

1. Introduction 2. Materials and Methods - Origin of the material studied - Plant material preparation - Wood density 3. Definition of Anatomical Features - Xylem - Bark - Pith 4. Identification Keys - Wood without vessels - Wood with vessels and included phloem - Wood with vessels and without included phloem 5. Anatomical Description of Species - Gymnosperms * Cupressaceae * Pinaceae * Taxaceae - Gnetales * Ephedraceae - Angiosperms Monocotyledonous * Asparagaceae * Graminaceae * Ruscaceae * Smilacaceae - Angiosperms Dicotyledonous * Adoxaceae * Amaranthaceae * Anacardiaceae * Apocynaceae * Aquifoliaceae * Araliaceae * Aristolochiaceae * Asclepiadaceae * Asteraceae * Berberidaceae * Betulaceae * Boraginaceae * Brassicaceae * Buxaceae * Caesalpiniaceae * Cannabaceae * Capparaceae * Caprifoliaceae * Caryophyllaceae * Chenopodiaceae * Cistaceae * Convolvulaceae * Cornaceae * Dipsacaceae * Ebenaceae * Elaeagnaceae * Ericaceae * Euphorbiaceae * Fabaceae * Fagaceae * Frankeniaceae * Hypericaceae * Juglandaceae * Lamiaceae * Lauraceae * Lythraceae * Malvaceae * Mimosaceae * Moraceae * Myrtaceae * Oleaceae * Orobanchaceae * Platanaceae * Plumbaginaceae * Polygonaceae * Ranunculaceae * Rhamnaceae * Rosaceae * Rubiaceae * Rutaceae * Salicaceae * Sapindaceae * Simarubaceae * Solanaceae * Styracaceae * Tamaricaceae * Thymelaeaceae * Ulmaceae * Verbenaceae * Vitaceae * Zygophyllaceae List of Species and Families References

Review of macroscopic features for hardwood and softwood identification and a proposal for a new character list

With the adoption of a number of anti-illegal logging laws, treaties, memoranda, and international agreements around the world, there is broad and renewed interest in wood identification, especially in the field at the macroscopic level. In response to this interest, and to begin to fill an obvious gap in the corpus of wood anatomical reference material, we review several prominent English-language publications on macroscopic wood identification in order to form a list of characters. We compile characters and organize them in the spirit of the IAWA lists for hardwood and softwood microscopic identification, present the state of the art as it exists, attempt to reconcile the different sets of definitions, characters, and character states, then present our proposed working-list. It is our intent with this publication to open an international discussion regarding the standardization of macroscopic wood identification features, and it is our hope that such a discussion can include critical works from the non-English literature. We also call for an illustrated glossary to accompany the proposed list. A standard lexicon to describe wood at the macroscopic level will simplify the preparation of identification documents and permit the ready translation of keys and other references for easy use and deployment around the world.

The “blue ring”: anatomy and formation hypothesis of a new tree-ring anomaly in conifers

Key messageDouble-stained microsections from highaltitudePinus nigrawood cores highlighted unlignified latewood cells possibly linked to abrupt temperature reduction at the end of the growing season. More consolidated detection could increase their role in dendroecology.AbstractCambial activity and wood formation are influenced by environmental factors, primarily climate. During cell wall formation the lignification is mainly controlled by temperature. By staining with safranin and astra blue it is possible to distinguish cell walls richer in lignin (stained in red) from those richer in cellulose (stained in blue). Here we show an uncommon phenomenon observed in 41 transverse sections prepared for anatomical studies of young European black pine (Pinus nigra Arnold) individuals. We detected some layers of incompletely lignified cells that appear blue in safranin–astra blue-stained sections. Growth rings showing this anatomical feature were named “blue rings”. The aims of this preliminary study are: (i) to describe the features of this peculiar anatomical trait, (ii) to enhance its visualization, and (iii) to suggest possible drivers of its formation. First results indicate the influence of low air temperature causing a lack of lignification in latewood cells. The added values provided by the identification of “blue rings” within tree-ring series could be (i) their possible use as pointer year, (ii) cross dating improvement, and (iii) finer assessment of tree sensitivity to environmental and climatic factors.

TRACHEID AND PIT ANATOMY VARY IN TANDEM IN A TALL SEQUOIADENDRON GIGANTEUM TREE

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.

Relationship between local and global modulus of elasticity in bending and its consequence on structural timber grading

The study analyses the relationship between local and global modulus of elasticity and develops and evaluates different models to predict local from global modulus measurements. The mechanical tests were performed on four species commonly used in Italy for structural purposes: fir, Douglas-fir, Corsican pine and chestnut. Two or three cross-sections and two provenances were sampled for each species. A theoretical analysis showed that the local–global modulus relationship was of polynomial form with only one coefficient. The effect of the species on the relationship was significant as well as the cross-section but only for softwoods. The effect of the cross-section was explained by the presence and the size of defects in the mid span. The different models were applied and then compared by means of the optimum grading: only slight differences among models emerged. Although optimum grading was strongly dependent on the sampling and on the grade combination, for softwoods the model for species and section showed very similar results to the grading with the true local modulus; inclusion of the knot values in the model led to only slight improvements. For chestnut all models were found to be comparable.ZusammenfassungDiese Studie untersucht den Zusammenhang zwischen lokalem und globalem E-Modul von Schnittholz und entwickelt und vergleicht verschiedene Modelle, um den lokalen E-Modul aus globalen Messungen zu bestimmen. Die Versuche wurden an vier in Italien häufig als Bauholz verwendeten Holzarten durchgeführt: Tanne, Douglasie, Korsische Schwarzkiefer und Edelkastanie. Je Holzart wurden zwei oder drei Querschnitte aus jeweils zwei Wuchsgebieten beschafft. Eine theoretische Untersuchung zeigte, dass der Zusammenhang zwischen lokalem und globalem E-Modul einer Polynom-Funktion mit nur einem Koeffizienten entspricht. Signifikanten Einfluss auf den Zusammenhang hatte die Holzart und bei Nadelhölzern auch der Querschnitt, was durch das Vorhandensein und die Größe der Äste im mittleren Prüfbereich begründet wurde. Die verschiedenen Modelle wurden angewandt und bezüglich ihrer Auswirkung auf die optimale Sortierung verglichen: Es zeigten sich nur geringe Unterschiede. Obwohl die optimale Sortierung sehr stark von der Probenahme und der Sortierklassen-Kombination abhing, führte das Modell auf Basis von Holzart und Querschnitt bei den Nadelhölzern zu sehr ähnlichen Ergebnissen wie eine Sortierung nach dem gemessenen lokalen E-Modul; die Berücksichtigung der Astwerte führte nur zu geringen Verbesserungen. Für die Edelkastanie waren alle Modelle vergleichbar.

The Great Timber Roof of Porta Nuova Railway Station in Turin: The Role of Assessment and Diagnosis for Sustainable Repair and Conservation

ABSTRACT This article illustrates a wide multidisciplinary project carried out as part of recent restoration works of the great timber roof of Porta Nuova Railway Station in Turin (Italy). The station was built in 1861 (project by A. Mazzucchetti and A. Castigliano), when Turin was the first capital of Italy. In recent years, the roof needed important maintenance and restoration interventions due to water leaking which caused the decay of the timber structure. The original roof was under threat also because there was a proposal for the complete substitution of the timber elements (in a total of 2350 m2). However after accurate assessment and diagnosis (following recent regulations) it was possible to save the original timber structure and to plan and realize sustainable interventions for repair and conservation with innovative technologies. This was carried out within a complex restoration site of the whole building.