1,721,085 research outputs found
Comparative axial widening of phloem and xylem conduits in small woody plants
No full textPlant 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
Basipetal widening of xylem and phloem conduits along the stem in different woody species
No full textEXPERIMENTAL TEACHING IN WOOD TECHNOLOGY
No full textThe purpose of this work is to present certain procedures and equipments that were implemented in the course of Xilology and Wood Technology held at the University of Padua. The objective was to offer to the students the opportunity to directly attend some experiments, usually explained only in theory.
In the first level degree course in Wood Technology and Timber Industry, the course of Xilology and Wood Technology ranges from biological characteristics of the wood material up to its physical and mechanical performance, a wide review with the intended purpose to form wood technologists. In the course program wide spaces should be left to the practise and applicative aspects, from microscopic observations of woody
plant tissues to physical and mechanical properties determinations. The experimental educational approach,
as known, helps the understanding of content and, above all, allows to understand the mechanisms underlying the experiments.
However, the need to combine educational activities with practical experience done directly by the students in a conventional classroom, crashes with the difficulty concerning the equipment and the time required for carrying out the experience. The equipment required for a basic exercise in wood technology range from common laboratory equipment, normally present in educational Faculty workshops, to sophisticated and
specific test machines, expensive and used only by properly trained technicians.
Here we present simple equipment, specially set up for student self use, designed to carry out static tests on wood samples in order to determine the mechanical parameters module of rupture and module of elasticity in an easy and safe way.
From the other way, some determinations can not be carried out in the classroom because they require an incompatible time period for the educational programming of the lessons. For example in the study of the relations between wood and water, it is necessary to completely dehydrate wood. This operation is, in the proper way, conducted in an oven and requires a long time (1-4 days). In order to perform determinations related to wood water content is here explained a set up procedure that runs through microwave drying, that produces certain results in a lower time
Wood, bark and pith structure in trees and shrubs of Cyprus: anatomical descriptions and ecological interpretation
Full text linkThe dissertation deals with wood, bark and pith anatomy of trees and shrubs of Cyprus. It consist of three parts: (1) the anatomical description of stem wood, twig bark and pith of the endemic and indigenous trees and shrubs species belonging to the flora of the island, (2) the ecological wood and bark anatomies interpretation and (3) a study focused on conductive vs. mechanical tradeoff in climbers vs. subshrubs.
Original samples for each species were collected during 3 field trips on Cyprus. About 270 species were collected, and 600 double stained (astra blue and safranin) slides were prepared. New lists of anatomical features were developed for the specific needs of this research, especially for bark and pith anatomy. The described species represent almost the entire woody flora of the island. A great number of them have never been anatomically described before. The anatomical descriptions are a perfect base for wood anatomists interested to wood structure of single species or the range of anatomical patterns within the Eastern Mediterranean region, and also for archeologist and palaeobotanists who determine wood remains, and for wood technologist who compare structures with physical wood properties.
In the ecological wood anatomy analysis we observed wood diffuse porous structure associated to woody chamaephytes. We detected semi-ring and ring porous xylems related to nanophanerophytes and phanerophytes. Rays features seem to be associate to space filling in wood, and the rays dimensional features seems to be constrained by vessels. In fact, rays became larger moving from woody chamaephytes to phanerophytes, and the numbers of rays per millimeter decrease moving from woody chamaephytes to phanerophytes, maybe allowing vessels to be greater in taller life forms. Raylessness is clearly associated to woody chamaephytes. Rays composition vary from homogeneous in woody chamaephytes, to heterogeneous in nanophanerophytes and phanerophytes. The axial parenchyma was rare in woody chamaephytes, apotracheal in nanophanerophytes and mainly paratracheal in phanerophytes. Endemic species showed absence of axial parenchyma, raylessness, homogeneous rays, and did not show association to tension wood. We recorded a predominance of diffuse porous species in dry/hot site, and the presence of ring porous species in wet/cold sites. Diffuse porous structures were associated to rocky and sandy sites, and semi-ring porous woods to forest and shrublands habitats. Thick walled fibers species were associated to moist and ruderal habitats, thin walled fibers to forest and shrubland species. A clear trend was observed in fiber wall thickness vs. wood density: greater in the fiber wall thickness, greater is the wood density.
The bark anatomical features describe sieve tube morphology and distribution, sclerenchyma presence and arrangement, rays, phellem, phelloderm, crystals, secretory structures, and appearance under polarized light. Sieve tubes were typically arranged tangentially in nanophanerophytes but not in woody chamaephytes. Bark ray dilatation was noted in moist site species but lacking in endemic, shrubland, and forest species. Sclerenchyma tended to be lacking in woody chamaephytes, and in endemic and dry site species. The tangential arrangement of fibers tended to be lacking in woody chamaephytes and Mediterranean species. The presence of prismatic crystals was associated with nanophanerophytes and phanerophytes, but not with endemic, shrubland, or forest species. Phloem homogeneity was associated with endemic species. Phellem homogeneity was associated with climbers, phanerophytes, and species of moist habitats. The association of sclerenchyma with life form suggests a biomechanical role, especially for young twigs. The level of endemism and the species' habitat were strongly linked to a number of bark features opening new fields of ecophyletic and ecophysiological investigation.
In the third part of the dissertation the all sampled woody climbers (10 species) and most of the woody subshrubs (25 species) of Cyprus were characterized by their vessel and fiber anatomies relative to mechanical and hydraulic function. Consistent with their lower need for self-support, on average the climbers had lower wood density than did the subshrubs, and had a lower proportion of their cross-section devoted to fibers. Consistent with climbers’ need for higher hydraulic conductance and total plant height, climbers had vessel sizes and frequencies closer to the theoretical packing limit than did subshrubs.La tesi si occupa di anatomia del legno, della corteccia e del midollo di alberi e arbusti appartenenti alla flora dell'isola di Cipro. Si compone di tre parti: (1) la descrizione anatomica del legno del tronco, e di corteccia e midollo dei rametti, (2) l'interpretazione ecologica dell'anatomia del legno e della corteccia e (3) uno studio focalizzato sul compromesso delle funzioni di conduzione e di sostegno meccanico in liane a piccoli arbusti.
Nel corso di 3 campionamenti a Cipro sono stati raccolti campioni per circa 270 specie. Da questi sono stati realizzati 600 preparati anatomici a doppia colorazione (astra blu e safranina). Nuove liste codificate per la descrizione delle caratteristiche anatomiche della corteccia e del midollo sono state sviluppate appositamente per gli scopi di questa ricerca. Le specie descritte rappresentano quasi l’intera flora legnosa dell’isola. Un gran numero di specie sono qui descritte prima dal punto di vista anatomico. Le descrizioni anatomiche sono una base perfetta per anatomisti legno interessati alla struttura in legno di singole specie o allo studio della gamma di modelli anatomici nella regione del Mediterraneo orientale, e anche per archeologi e paleobotanici che hanno la necessità di identificare reperti legnosi, e anche per tecnologi del legno che confrontano le strutture anatomiche con le proprietà fisiche e meccaniche del legno.
Le indagini di ecologia del legno hanno rilevato relazioni statisticamente significative tra legno a porosità diffusa e camefite legnose, mentre le porosità semi diffusa e anulare sono legate alle nanofanerofite e alla fanerofite arboree rispettivamente. Le caratteristiche dei raggi sembrano associate al riempimento dello spazio nel legno e le dimensioni dei raggi in sezione trasversale sembrano limitate dai vasi. Infatti i raggi sono più larghi nelle fanerofite arboree che nelle camefite legnose e il numero di raggi per millimetro diminuisce passando da fanerofite arboree, a nanofanerofite fino alle camefite legnose, consentendo così alla forme biologiche con altezza maggiore di avere vasi più grandi. L'assenza di raggi è una caratteristica tipica delle camefite legnose. La composizione dei raggi varia da omogenea nelle camefite legnose a eterogenea in nanofanerofite e fanerofite arboree. Il parenchima assiale è raro o difficilmente osservabile nelle camefite legnose, tipicamente apotracheale nelle nanofanerofite e principalmente paratracheale nelle fanerofite arboree. Le specie endemiche a Cipro sono caratterizzate dall'assenza di parenchima assiale, dall'assenza di raggi o dalla presenza di raggi omogenei e non mostrano alcuna relazione significativa con la presenza di legno di tensione. È stata riscontrata una netta predominanza di specie a porosità diffusa nei siti caldi e secchi, e di specie a porosità anulare in siti umidi e freddi. Legni a porosità diffusa appartengono a specie che vivono in siti rocciosi e sabbiosi, la porosità anulare è associata ad habitat forestali e di macchia mediterranea. Le fibre a parete spessa risultano legate a a siti umidi, fibre a pareti sottili ad habitat forestali e di macchia mediterranea. Un chiaro trend lega proporzionalmente lo spessore delle fibre con la densità del legno.
Le caratteristiche anatomiche analizzate per la corteccia descrivono morfologia e distribuzione dei tubi cribrosi, la presenza e la disposizione di tessuti sclerenchimatici, i raggi, il sughero, il felloderma, i cristalli, le strutture di secrezione e la visibilità in luce polarizzata. I tubi cribrosi sono tipicamente disposti in bande tangenziali nelle nanofanerofite, ma non nelle camefite legnose. L'allargamento dei raggi nel felloderma è legato a specie che vegetano in siti midi, non è presente nelle specie endemiche, in quelle tipiche di macchia mediterranea a negli habitat forestali. I cristalli sono associati alle nanofanerofite e alle fanerofite arboree, non alle specie endemiche, di macchia e di ambiente forestale. L'omogeneità del felloderma è stata riscontrata nelle fanerofite lianose, in quelle arboree e alle specie di ambienti umidi. L'associazione di tessuti sclerenchimatici con le forme biologiche suggerisce un ruolo biomeccanico di questo tessuto, soprattutto nei giovani rametti. Il livello di endemico e l'habitat delle specie sono fortemente legati a diverse caratteristiche anatomiche della corteccia offrendo nuove possibilità di studio nel campo dell'ecologia e dell'ecofisiologia.
Nella terza parte che costituisce la tesi tutte le 10 specie di fanerofite lianose campionate e la maggior parte delle camefite legnose (25 specie) sono state caratterizzate per quanto riguarda le caratteristiche anatomiche di vasi e fibre che hanno ripercussioni importanti nelle funzioni di conduzione e di sostegno meccanico del legno. In accordo con la loro inferiore necessita di auto-sostegno, le fanerofite lianose hanno una densità basale inferiore rispetto alle camefite legnose. Inoltre, le liane presentano una inferiore proporzione di sezione trasversale destinata a fibre. In accordo con le maggiori necessità conduttive e in relazione alla loro altezza, le liane hanno un diametro e una frequenza dei vasi che le colloca più vicine al funzione "packing limit" rispetto alle camefite legnose
Atlas of wood, bark and pith anatomy of eastern Mediterranean trees and shrubs
No full textThis atlas presents anatomical descriptions of the xylem, bark and pith of 264 species belonging to 69 families. It highlights the anatomical diversity of trees, shrubs, dwarf shrubs, woody lianas and several of the prominent perennial herbs from the Eastern Mediterranean region, with a focus on the island of Cyprus. The island’s topography and biogeographic history combine to provide a wide range of habitats and diverse flora including widespread, endemic, and ornamental species.
The monograph for each species includes a description of the anatomical structures of the stem and twig xylem and the twig’s bark and pith, as well as color micrographs of double-stained sections of each of these plant parts. These entries are accompanied by a photograph and a brief description of the plant including stem wood density, height, habit, flower, leaf and fruit characteristics, and a map showing its geographic and altitudinal distribution in the region. Xylem descriptions follow the IAWA lists of microscopic features for hardwood and softwood identification. For bark and pith descriptions, a new coding system developed by the authors is applied. Lastly, the atlas offers a key for wood identification that was developed to differentiate between groups of species by using a small number of features that are unambiguous and clearly visible. The atlas will be a valuable guide for botanists, ecologists, foresters, archeologists, horticulturists and paleobotanists
Stem Anatomical Features of the Dicotyledons. Xylem, Phloem, Cortex and Periderm Structures for Ecological and Taxonomical Analyses
No full text
- …
