Vessel Element Length Research Articles

Ontogenetic wood anatomy of tree and subtree species of Nepalese Rhododendron (Ericaceae) and characterization of shrub species

Ontogenetic trends in the wood structure of Nepalese Rhododendron were studied in 15 specimens of two tree and four subtree species. Average growth ring width was constant from pith to bark in spite of occurrences of extremely narrow, false, or discontinuous rings. Vessel density, vessel area, vessel element length, and multiseriate ray height generally had an initial increase or decrease to 1.5 cm radius and near plateau or slight decrease or increase outward. Multiseriate ray density and area percentage were variable between specimens without a clear pattern. Ontogenetic trends from pith to fully mature wood in trees plus subtrees were inferred by treating the measurements in the present study with those of mature individuals in a previous study. Comparison of trends in trees plus subtrees and those in shrubs lead to ecological or systematic groupings. Vessel features showed that alpine shrub species have distinctly small, numerous vessels composed of short vessel elements. Multiseriate ray features indicated a systematic difference between the trees plus subtrees of subgenus Hymenanthes and the shrubs of subgenus Rhododendron. Vessel features of alpine shrubs may be an adaptation against frequent freeze-thaw cycles or the result of growth stress imposed by the severe alpine environment.

Latitudinal trends in wood anatomy within species and genera: case study in Cornus s.l. (Cornaceae)

Latitudinal trends in wood anatomical characters in three Asiatic species of Cornus sensu lato (s.l.) were studied and compared with those for the whole genus based on an extensive sampling covering the specific distribution ranges and the generic data from a previous study. We studied 124 specimens of C. controversa growing between 31.5° and 45.3° N, 54 of C. kousa between 24.4° and 40.5° N, and 64 of C. macrophylla between 27.8° and 41.0° N. Characters studied were vessel element length, fiber length, vessel frequency, tangential vessel diameter, and vessel grouping index. At the species level no latitudinal trends were detected throughout the distribution ranges of the species. Neither tree size, altitude, nor climatic factors had a significant correlation with wood anatomical characters. In contrast, at the genus level, latitudinal trends were significant not just for the whole genus, but for both New and Old World species groups. At the genus level, latitude and three climatic factors all had a significant correlation with wood anatomical characters, but correlation coefficients with latitude were markedly high. The difference in latitudinal trends between the genus and species levels may be due to the radiation of Cornus along paleoclimatic gradients in the early Tertiary.

WOOD CHARACTERISTICS OF AMAZON FOREST TYPES

The Tambopata region of the southern Peruvian Amazon supports a high diversity of both woody plants and forest types. Woods collected from low riverside vegetation, floodplain forest, clay-soil forest on an upper terrace, sandy-soil forest, and swamp forest provide an opportunity to test for significant differences in quantitative anatomical characters among forest types. Vessel-element length in floodplain-forest trees is significantly greater than in the other forest types. Specific gravity is lower in the two early-successional associations (low riverine forest and mature floodplain forest). Vessel diameter and density do not show significant differences among forest types and may be responding to overall climate controls. These two characters, however, show a pattern of variation within a transect extending back from the river along a gradient of increasing substrate and forest age; in addition, sites characterized by frequent flooding or presence of standing water lack vessels in the wider-diameter classes. The six characters analyzed show distributions that are, with the exception of wood specific gravity, significantly nonnormally distributed, a consideration that may be important in representing characteristics of assemblages of taxa. The degree of variability seen in some of the quantitative characters shows the importance of either basing analysis on adequate sample sizes or identifying robust indicators that can be used with small samples.

Variations in the Lengths of Fusiform Cambial Cells and Vessel Elements in Kalopanax pictus

Samples of a mature specimen of Kalopanax pictus, a ring-porous hardwood, were studied to compare the respective lengths of fusiform cambial cells and vessel elements in the stem. The lengths of dormant and reactivated fusiform cambial cells were measured with a confocal laser scanning microscope in tissue that had been macerated by digestion with pectinase and in thick tangential sections. The lengths of early wood and late wood vessel elements were measured in tissues that had been macerated by Franklin's method. The vessel elements and fusiform cambial cells varied considerably in length within individual samples. The mean length of early wood vessel elements corresponded to that of fusiform cells in the dormant cambium but not in the reactivated cambium. Significant differences were observed between the mean lengths of dormant and reactivated fusiform cambial cells, between those of reactivated fusiform cambial cells and early wood vessel elements, between those of reactivated fusiform cambial cells and late wood vessel elements, and between those of early wood and late wood vessel elements. The frequency distributions of lengths of cambial cells were bimodal and differed from those of vessel elements, which more closely resembled a normal distribution. The proportion of shorter lengths was higher in the reactivated cambium than in the dormant cambium, the early wood and the late wood vessel elements. Our results do not suppot the hypothesis that the lengths of early wood vessel elements in ring-porous hardwoods change during differentiation. The similar ranges of recorded lengths suggest that short and long vessel elements might be derived directly from short and long cambial cells, respectively.

Anatomía de la madera de Anacardiaceae con énfasis en los géneros americanos

An overview of systematic wood anatomy is presented and a synthesis of wood characters for 29 of the 32 genera of Anacardiaceae distributed in America is given. The analys is showed that wood of American genera has the divers ity observed for the Anacardiaceae as a whole. There is a high in cidence of genera with ring-porous wood in America compared to o ther continents. Also shorter vessel element and fiber lengths occur in genera distributed in America. The comparative studies that used wood features for Anacardiaceous genera such Anacardium, Astronium, Myracrodnwn, Pistacia, and Tapirira showed that qualitative and quantitative characters help to distinguish species. The neecl for increasing wood collections of Rhus, Schinus, and Toxicodendron species is emphasized.

Hidrosystem anatomical features of principal woody plants of Chaco, Argentina

Selected wood anatomy characteres of fourty six species of the principal trees of the Chaco Region were studied in order to analyze the hydraulic conductivity and safety of the xylem system, and compared with data from other habitats. Wood microscopic features considered were: ring porosity, vessel arrangement, tangential vessel diameter, number of vessels per mm2, Vulnerability Index, vessel element length, perforation plate, helical thickening and tracheas. A predominance of characters that probably contribute to hydraulic safety was observed: diffuse porous, numerous grouped or multiple vessels of small diameter, short vessel elements, with simple perforation plate. Maytenus vitis-idaea, Rupretchia apetala, Castela coccinea, Parkinsonia aculeata, Jodina rhombifolia species of the driest part of Chaco Region, present the most xerophytic features.

Leaf morphology, leaf chemical composition and stem xylem characteristics in two Pistacia (Anacardiaceae) species along a climatic gradient

Summary Leaf and stem xylem features in Pistacia lentiscus (an evergreen shrub) and P. terebinthus (a deciduous shrub) were analysed along an Atlantic-Mediterranean gradient, which is characterised by a variation of rainfall and winter temperature. Leaf features were foliage area of 3-year-old shoots (FA), leaflet area (LA), specific mass (SLM), thickness (LTh), density (LD) and chemical composition on a dry weight basis (N, P, cellulose Cel, hemicellulose Hcel, and lignin Lig). Stem traits referred to xylem anatomy: mean vessel diameter of the 25 largest vessels (MxD), vessel element length (VEL), number of vessels per xylem cross section area unit (VD) and the ratio xylem/foliage surface of shoots (HV). Comparisons of traits have been made both at an interspecific and at an intraspecific level, this latter by analysing how these traits respond to variations of precipitation and winter temperature. P. terebinthus showed higher FA, LA, MxD, Nand Cel, but lower SLM, LTh, Hcel, VD and HV than P. lentiscus. Both species showed opposite responses of LTh to the reduction of mean minimum January temperature, decreasing in the former and increasing in the latter. In P. lentiscus VD increased and VEL decreased when winter temperature became colder, while YD decreased and N increased towards the arid part of the gradient. It is suggested that leaf habit plays an important role in determining the function of species and their response to the climatic gradient.

Stem xylem features in three Quercus (Fagaceae) species along a climatic gradient in NE Spain

Stem xylem features in two evergreen Quercus species (Q. coccifera and Q. ilex) and a deciduous one (Q. faginea) were analysed along an Atlantic-Mediterranean climatic gradient in which rainfall and winter cold experience strong variation. Mean maximum vessel diameter, vessel density, vessel element length, xylem transverse sectional area, Huber value (xylem transverse sectional area per leaf area unit), theoretical leaf specific conductivity (estimated hydraulic conductance per leaf area unit) and total leaf area were determined in 3-year-old branches. Q. faginea presented the widest vessels and the highest theoretical leaf specific conductivity while Q. coccifera showed the lowest total leaf area and the highest Huber value. Studied features did not exhibit significant correlations with mean minimum January temperature in any species but did show significant relationships with rainfall. In Q. coccifera, mean maximum vessel diameter, vessel element length and theoretical leaf specific conductivity increased with higher rainfall while vessel density decreased. Mean maximum vessel diameter and total leaf area in Q. ilex increased with precipitation whereas variables of Q. faginea did not show any significant trend. Results suggest that aridity, rather than minimum winter temperature, controls stem xylem responses in the studied evergreen species. Q. faginea traits did not show any response to precipitation, probably because this species develops deep roots, which in turn makes edaphic and topographic factors more important in the control of soil water availability. In response to aridity Q. coccifera only exhibits adjustment at a xylem level by reducing its water transport capacity through a reduction of vessel diameter without changing the amount of xylem tissue or foliage, whereas Q. ilex adjusts its water transport capacity in parallel to the foliage area.

Development of cambium and length of vessel elements and fibers in dwarfAlnus hirsuta (Spach) rupr

In a comparison of cambial cells and their derivatives between naturally occurring dwarf and normal trees, vessel elements and fibers in the annual rings of dwarf trees were found to be shorter, narrower and fewer than those of normal trees. The frequency of anticlinal divisions and loss of cambial initials were low during the differentiation of xylem cells from cambial initials in dwarf trees. The length and intrusive growth of fusiform initials were slightly less than those of normal trees. Thus, it was concluded that the shortening of vessel elements and fibers in dwarf trees was due to the fact that cambial initials were themselves shortened and underwent inactive intrusive growth during differentiation of the xylem mother cells.

Wood and bark anatomy of the African species of Gnetum

Quantitative and qualitative data are given for the two African species of Gnetum (Gnetum section Gnetum subsection Micrognemones). These species are lianoid and lack the fibre-tracheids of G. gnemon but have about the same vessel element and tracheid length as in that species. Vessel diameter is related to stem age and organography. Tori are clearly present in tracheary elements of the African Gnetum species, a first report for the genus. In these two species, origin of the lateral meristem, which produces vascular tissue and cambia, can be traced directly and indirectly to cortical parenchyma. A second kind of meristematic action, newly reported for Gnetum, is produced by proliferation of axial parenchyma, fragmenting secondary xylem. Both presence of tori and site of origin of lateral meristematic activity in Gnetum contrast with corresponding conditions in Welwitschia.

Relationships Between Water Availability and Selected Vessel Characteristics in Eucalyptus Grandis and Two Hybrids

The primary objective of this study was to determine the relationships between water availability, plant growth and selected vessel characteristics for Eucalyptus grandis and two hybrids, so as to ascertain whether these xylem characteristics predict water use efficiency. Cuttings of Eucalyptus grandis, E. grandis × camaldulensis and E. grandis × nitens were planted in 220 litre drums from which rainfall was excluded. One half of the individuals received a low watering treatment; one half received a higher watering treatment. Soil moisture depletion through root uptake was monitored weekly and the removed water replaced to maintain 60 and 80 litres in the pots of the low and high watering treatments respectively. Mean values for tangential vessel diameter, vessel frequency and vessel element length were compared for the two treatments. In E. grandis and the hybrid E. grandis × camaldulensis vessel diameter (P < 0.01 ' P < 0.05 respectively) and vessel element length (P < 0.05 for both) increased from the dry to the wet treatment as water uptake through transpiration increased. There is no significant correlation between available water and vessel frequency. For E. grandis × nitens, on the other hand, only vessel frequency was significantly (P < 0.01) correlated with water uptake. In all three species/hybrids water availability also had a significant influence on stem diameter (P < 0.0001) and transverse sectional stem area (P < 0.0001) which increased with increased water consumption. These results suggest that E. grandis × nitens may be more water use efficient than E. grandis, which is commonly grown for timber and thus could potentially be used as a replacement species that is more water conservative in this water limited region.

Ecological wood anatomy ofAlnus nepalensis (Betulaceae) in East Nepal

Wood anatomical characters ofAlnus nepalensis growing in East Nepal are evaluated against three non-anatomical factors: tree height, diameter at breast height (DBH), and altitude. Samples were taken from the outermost part of the trunk of five canopy trees at 11 localities between 790 and 2,740 m above sea level. Tree height ranged from 10 to 28 m, and DBH ranged from 15 to 80 cm. Altitude and tree height are correlated with all the vessel characters studied. Among wood anatomical characters, vessel characters measured from cross sections are strongly correlated with one another, and are also correlated with vessel element and fiber-tracheid length. Multiple regression analysis using non-anatomical factors as independent variables resulted in significant correlation at 1% level in all pore characters, vessel element length, perforation plate bar number, and fibertracheid length. Regression coefficients of significant regressions are usually largest for altitude. For wood structure ofAlnus nepalensis in East Nepal, 23 to 42% of the variation is affected by non-anatomical factors. The large contribution of altitude is considered to be an indirect measure of the effect of temperature.

Allometric neoteny and the evolution of succulence in cacti

Abstract With the objective of analysing the role of heterochrony in the evolution of succulence in the cactus family, a comparative study of xylem development in six species with contrasting morphologies was carried out. Two woody leaf-bearing cacti and four succulent cactus species belong to different subdivisions within the family were analysed. In each species and for different ages, vessel-element length was measured, vessel-element lateral wall-pitting described and the percentage of xylem and parenchyma in the stem quantified. In the succulent species it was found that vessel element length did not change between juvenile and adult wood, that wall-pitting in adult plants was similar to that of seedlings, and that the woody tissue in adult plants was organized in vascular bundles as in the primary tissue of seedlings. Leaf-bearing cacti, in contrast, changed in both vessel element length and wall-pitting when secondary wood was produced, and the secondary woody tissue of adult plants was organized in a continuous cambial cylinder as in most dicotyledons. An allometric analysis suggests that a retardation in the developmental rate of woody tissues (allometric neoteny) is the main mechanism in the development of succulence in cacti.

Allometric neoteny and the evolution of succulence in cacti

With the objective of analysing the role of heterochrony in the evolution of succulence in the cactus family, a comparative study of xylem development in six species with contrasting morphologies was carried out. Two woody leaf-bearing cacti and four succulent cactus species belong to different subdivisions within the family were analysed. In each species and for different ages, vessel-element length was measured, vessel-element lateral wall-pitting described and the percentage of xylem and parenchyma in the stem quantified. In the succulent species it was found that vessel element length did not change between juvenile and adult wood, that wall-pitting in adult plants was similar to that of seedlings, and that the woody tissue in adult plants was organized in vascular bundles as in the primary tissue of seedlings. Leaf-bearing cacti, in contrast, changed in both vessel element length and wall-pitting when secondary wood was produced, and the secondary woody tissue of adult plants was organized in a continuous cambial cylinder as in most dicotyledons. An allometric analysis suggests that a retardation in the developmental rate of woody tissues (allometric neoteny) is the main mechanism in the development of succulence in cacti.

Eco-Anatomical Wood Features of Species from a Very Dry Tropical Forest

In 19 species of a very dry forest in Venezuela vessel diameter, vessel frequency, vessel grouping, vessel element length, and intervessel pit size, were studied and compared with data from other habitats. A predominance of characters that presumably contribute to hydraulic safety was observed: numerous grouped vessels of small diameter, short vessel elements, and minute intervessel pits. In some species, a xeromorphic wood anatomy coexists together with adaptations such as deciduousness, xeromorphic foliage, deep or superficially-extended roots, and succulence. In other species studied, the presence of xerophytic adaptations such as assimilating stems, succulence, and deep roots, seem to mitigate the xeromorphic wood appearance and, to some extent, lend it a mesomorphic character.

Radial Variation and Growth Rate in the Length of the Axial Elements Of Sessile Oak Wood

Radial variability of the axial element length in oak-wood is most prominent in the juvenile wood which inc1udes approximately 30 annual rings. The length of fibres, tracheids and vessel elements increases from the pith outwards according to a second degree curve. This dependence is most apparent for wood fibres, whereas it is the least distinct for vesseI elements. In the mature zone, anatomical elements are, on average, 10 to 20% Ion ger than in juvenile wood. With deteriorating conditions of tree growth, the length of the anatomical elements tends to increase. There is a negative correlation between length of the measured elements and growth ring width; this is most c1early so for fibres. A similar relationship exists between the length of anatomical elements and wood density.

Wood Anatomy of Elm (Ulmus) and Hackberry (Celtis) Species Native to the United States

Wood anatomy of Ulmus and Celtis species (Ulmaceae) native to the United States is described. Ulmus differs from ring-porous species of Celtis in ray structure, crystallocation, and colour and fluorescence of water extracts. The soft elms/non-winged bark species (Ulmus americana and Ulmus rubra) differ from the hard elms/winged bark species (U. alata, U. crassifolia, U. serotina, and U. thomasii) in density, earlywood pore diameter, and appearance of crystal-containing axial parenchyma. Some species of hard elm can be distinguished from one another by a combination of characters: water extract colour and fluorescence, earlywood pore diameter and spacing. The anatomy of ring-porous species of Celtis is unifonn, except that in C. reticulata earlywood pores have a smaller radial diameter than the other species. Celtis pallida is diffuse-porous and resembles other diffuse-porous species of the genus. Vessel element lengths are similar for all species within these two genera regardless of habitat.

Wood Anatomy of Papaveraceae, with Comments on Vessel Restriction Patterns

Qualitative and quantitative features are reported for Bocconia, Dendromecon, Dicentra, Hunnemannia, and Romneya. Bocconia differs from the other genera by its wide vessels, few per group, and few per mm2; it shows paedomorphosis in vessel element length and ray histology. In respects other than these, it agrees with features common to woody Papaveraceae; these features in turn occur in families of Papaverales (Berberidaceae, Lardizabalaceae, Ranunculaceae): vessels in diagonal groups; presence of both libriform fibres and vasicentric tracheids; nucleated nature of libriform fibres; rays almost exclusively multiseriate; rays wide, tall, and composed mostly of procumbent cells; wood storied to various degrees. Additional features show resemblance between one or more genera of Papaveraceae and other families of Papaverales. Bocconia is distinctive among Papaveraceae in its relatively mesomorphic wood, which may in part be explainable on the basis of stern succulence. The occurrence of avessei restriction pattern - vessels in the centre of fascicular areas (axial portions of secondary xylem between rays) not in contact with rays - in Dicentra and Hunnemannia is like that of other genera of Papaverales such as Nandina. An explanation for the significance of vessel restriction, involving genera other than those of Papaverales (Launea, Valeriana), is attempted.

Características de la madera de Cedrela odorata L (cedro amargo, Meliaceae) en Costa Rica.

Cedrela odorata L. is a deciduous tree 30-35 m height and 1.5 m in diameter, native to Costa Rica, which grows in areas ranging from 1500-3000 m.s.n.m. The wood has coarse and heterogeneous texture, linear grain and superposed areas in tangential section with 2-4 growth rings 12.5 cm. Porosity is diffuse, circular or semicircular. There is variation in pore size, vessel element length, fiber length, cell wall thickness of fibers and ray composition between specimens collected at different localities. Runkel factor corresponds to Group IV, regular for pulp production; however, the physical and mechanical characteristics show the wood to be excellent for building and cabinetwork.

Dicotyledonous woods from the Upper Cretaceous of southern Illinois

Five species of fossil dicotyledonous wood are described from an Upper Cretaceous (Maestrichtian; locality in Alexander County, IllinoiS. U.S. A.Paraquercimum cretaceum has structure similar to the Fagaceae (evergreen Oak-Lithocarpus) and Casuarinaceae and represents the earliest known occurrence of this structural type (large solitary pores and uniseriate and large multiseriale rays).Paraphyltanthoxyhin illirioisense and Icacinoxylon alternipunctata are species of genera represented at other Cretaceous and Early Tertiary localities In large diameter trees.Parabombacaceoxylon magniporosum has large diameter pores and scalariform perforation plates, a combination of characters that is extremely rare in the extant flora.Paraapocynaceoxylon barghoorni has a combination of characters represented in extant Apocynaceae. These five species lack growth rings, have high vulnerability indices (mean vessel diameter divided by mean number of vessels per square millimeter, and a relatively high proportion of ray parenchyma. They lack specialized wood anatomical characters, and a compilation of vessel element lengths in these and other Cretaceous woods indicates that short vessel elements (a derived character) were less frequent in the Cretaceous than in extant dicotyledonous trees.