scholarly journals Contramolde medular em conexão orgânica com fragmento lenhoso de Retemedulloxylon da Formação Rio Bonito (Eopermiano da Bacia do Paraná), Santa Catarina, Brasil

1999 ◽  
Vol 26 (2) ◽  
pp. 73
Author(s):  
SHEILA MERLOTTI
Keyword(s):  
Secondary Xylem ◽  
Environmental Influences ◽  
Longitudinal Axis ◽  
Fossil Wood ◽  
Cylindrical Shape ◽  
Santa Catarina ◽  
Taxonomic Affinity ◽  
Primary Xylem ◽  
Secondary Wood ◽  
Wood Fragment

This work records the occurrence of a pith cast connected with wood fragment in a fossil assemblage proceeding from Pouso Redondo County, Santa Catarina State, Brazil, in sediments from the Rio Bonito Formation, Eopermian of the Paraná Basin. The pith cast, cylindrical, is highly siliceous and unprovided of diagnosis impressions and tissular vestiges. The fragment, which has a half-cylindrical shape and a concavity along the longitudinal axis, is devoid of primary xylem and reveals a secondary xylem with few defined axial and radial systems. The anatomic characteristics of the secondary wood body indicate taxonomic affinity of the fossil wood with the most representative genus in the assemblage, increasing the establishing of relationships between the pith casts and the gondwanic taxa describe until the present, and suggest that the occurrence of these pith casts in the gondwanic sediments is probably because of environmental influences.

scholarly journals Um Novo Lenho Gimnospérmico da Formação Rio Bonito, SC, Brasil - Aterradoxylon solidum gen. et sp.nov.

1999 ◽  
Vol 26 (2) ◽  
pp. 79
Author(s):  
SHEILA MERLOTTI
Keyword(s):  
South Africa ◽  
Secondary Xylem ◽  
Vascular System ◽  
Fossil Wood ◽  
New Taxon ◽  
Santa Catarina ◽  
Bordered Pits ◽  
Secretory System ◽  
Primary Vascular System

The morphoanatomic study of a taphoflora from the Rio Bonito Formation, Pouso Redondo County, Santa Catarina State, Brazil, resulted in the determination of new gymnospermous genera, among them a fossil wood that, by being represented by 9 of the 25 samples studied, constitutes the second form with significant representation in the assemblage (36%). By virtue of the solid and heterocelular pith, the centrifugal differentiation of the primary vascular system and the large pits in the cross-field of the secondary vascular system, the wood in question is similar to the morfogenus Megaporoxylon KRÄUSEL, 1956 from the Permian of South Africa. However, the presence of singular characters, like the nature of the secretory system and the outline of pith as well as the configuration of the bordered pits on radial walls of the secondary xylem cells, evidences the necessity of its segregation in new taxon which is named Aterradoxylon solidum gen. et sp. nov.

scholarly journals RESILIENCE OF FERNS: WITH REFERENCE TO DESICCATION AND REHYDRATION STRESS OFFER NEW INSIGHTS

2017 ◽  
Vol 4 (2) ◽  
pp. 89-94
Author(s):  
Kavitha C.H ◽  
Meenu Krishnan ◽  
Murugan K
Keyword(s):  
Vascular Plants ◽  
Stress Proteins ◽  
Secondary Xylem ◽  
Plant Water Relations ◽  
Vascular Bundles ◽  
Late Cenozoic ◽  
Primary Xylem ◽  
Hydraulic Failure ◽  
Pit Membrane ◽  
Selection For

Ferns are one of the oldest vascular plants in existence and they are the second most diverse group of vascular plants followed to angiosperms. To unravel fern success has focused on the eco-physiological power and stress tolerance of their sporophyte and the gametophyte generations. In this context, those insightsencompass plant water relations, as well as the tolerance to and recovery from drought or desiccation stresses in the fern life cycle are reviewed. Lack of secondary xylem in ferns is compensated by selection for efficient primary xylem composed of large, closely arranged tracheids with permeable pit membranes.Protection from drought-induced hydraulic failure appears to arise from a combination of pit membrane traits and the arrangement of vascular bundles. Features such as tracheid-based xylem and variously sized megaphylls are shared between ferns and more derived lineages, and offer an opportunity to compare convergent and divergent hydraulic strategies critical to the success of xylem-bearing plants. Similarly the synthesis and accumulation of sugar, proline and stress proteins along with the production of pool of polyphenols add strength to desiccation stress. Thus, it can possible to suggest that selection acted on the physiology in a synchronous manner that is consistent with selection for drought tolerance in the epiphytic niche, and the increasingly diverse habitats of the mid to late Cenozoic.

XIX.—Notes on the Kidston Collection of Fossil Plant Slides. No. I. The Anatomy of the Axis of Lepidodendron Brownii Unger sp., with special reference to the Relationship between this Stem and Lepidostrobus Brownii Unger sp.

1933 ◽  
Vol 57 (2) ◽  
pp. 547-555 ◽  
Author(s):  
Mary G. Calder
Keyword(s):  
Special Reference ◽  
Secondary Xylem ◽  
Fossil Plant ◽  
Botany Department ◽  
History Of ◽  
Secondary Wood ◽  
The University ◽  
The Relationship ◽  
Carboniferous Limestone ◽  
As If

The Kidston Collection of fossil plant slides in the Botany Department of the University of Glasgow contains a number of sections of a very notable stem labelled “Lepidodendron textum, Kidston, n.sp.” No mention is made of this species in any of Dr Kidston's publications, but the correspondence relevant to the Collection indicates the history of the slides. This may be briefly summarised.As early as 1883, Dr Kidston had received from Mr J. Coutts two sections (Nos. 51 and 52) of this stem, which had been collected by the latter at East Kilbride, Lanarkshire, Scotland, from the Carboniferous Limestone Series of the Calderwood Beds (Hosie Limestone) in the Lower Limestone Group. Dr Kidston postponed description of this stem till he had better sections at his disposal; the specimen, however, was lost, and it was not till many years later that he rediscovered it in Dr John Young's collection in the Glasgow Municipal Museum, and had more sections cut from it (Nos. 1144–1153). No manuscript notes of Dr Kidston's descriptive of these slides have been found, with the exception of a pencilled reference in his manuscript slide catalogue, opposite Nos. 51 and 52, to the “foliar bundles—there is an appearance as if there was a development of secondary xylem, whereas the axial bundle has no secondary wood.”

scholarly journals WOOD ANATOMY OF THE VANGUERIEAE (IXOROIDEAERUBIACEAE), WITH SPECIAL EMPHASIS ON SOME GEOFRUTICES

IAWA Journal ◽  
2000 ◽  
Vol 21 (4) ◽  
pp. 443-455 ◽  
Author(s):  
Frederic Lens ◽  
Steven Jansen ◽  
Elmar Robbrecht ◽  
Erik Smets
Keyword(s):  
Pacific Ocean ◽  
Wood Anatomy ◽  
Secondary Xylem ◽  
Vessel Diameter ◽  
Underground Structures ◽  
Axial Parenchyma ◽  
Tropical Asia ◽  
Primary Xylem ◽  
The Pacific ◽  
The Pacific Ocean

The Vanguerieae is a tribe consisting of about 500 species ordered in 27 genera. Although this tribe is mainly represented in Africa and Madagascar, Vanguerieae also occur in tropical Asia, Australia, and the isles of the Pacific Ocean. This study gives a detailed wood anatomical description of 34 species of 15 genera based on LM and SEM observations. The secondary xylem is homogeneous throughout the tribe and fits well into the Ixoroideae s.l. on the basis of fibre-tracheids and diffuse to diffuse-in-aggregates axial parenchyma. The Vanguerieae include numerous geofrutices that are characterised by massive woody branched or unbranched underground parts and slightly ramified unbranched aboveground twigs. The underground structures of geofrutices are not homologous; a central pith is found in three species (Fadogia schmitzii, Pygmaeothamnus zeyheri and Tapiphyllum cinerascens var. laetum), while Fadogiella stigmatoloba shows central primary xylem which is characteristic of roots. Comparison of underground versus aboveground wood shows anatomical differences in vessel diameter and in the quantity of parenchyma and fibres.

Surgical studies on growth and xylem differentiation in the cotyledonary shoots of flax

1978 ◽  
Vol 56 (5) ◽  
pp. 476-482 ◽  
Author(s):  
M. V. S. Raju ◽  
W. N. Marchuk ◽  
Patricia L. Polowick
Keyword(s):  
Linum Usitatissimum ◽  
Secondary Xylem ◽  
Xylem Differentiation ◽  
Primary Xylem ◽  
The Third ◽  
Lateral Shoots

Growth and xylem differentiation in cotyledonary shoots were studied by partially isolating one shoot surgically in nondecapitated and decapitated flax plants (Linum usitatissimum var. noralta). Three types of cuts were made. The first type separated the shoot from the hypocotyl and the second from the epicotyl. The third type of cut was made at the node separating the two shoots, which, however, remained independently connected with the hypocotyl and epicotyl. In nondecapitated plants, the lateral shoots were inhibited. They had at their bases primary xylem strands, some of which were connected with the hypocotylary stele; the strands contained predominantly tracheids. In decapitated plants, the separated shoot grew vigorously when it was connected with both hypocotyl and epicotyl or hypocotyl alone. Such shoots contained at their bases abundant secondary xylem strands which were connected with the hypocotylary stele; the strands included predominantly vessels. The shoot that was isolated from the hypocotyl but connected with the epicotyl was inhibited even though it had abundant secondary xylem strands at its base. Results of this study suggest that growth of the cotyledonary shoot is dependent on the prior development of adequate xylem connections with the hypocotylary stele.

scholarly journals Learning from the past – the origin of wood

2008 ◽  
Vol 84 (4) ◽  
pp. 498-503 ◽  
Author(s):  
Rodney Arthur Savidge
Keyword(s):  
Cell Biology ◽  
Secondary Xylem ◽  
Secondary Growth ◽  
Wood Formation ◽  
Late Triassic ◽  
Primary Xylem ◽  
Tree Ferns ◽  
Severe Climate Change ◽  
Middle Carboniferous ◽  
Extinction Events

Trees were on Earth 394 million years ago (394 Ma) as spore-producing Archaeopteris progymnosperms having largediameter trunks of secondary xylem (morphotype Callixyon) produced by vascular cambium. Plants of smaller stature with primary xylem cores were present in Late Silurian (416 Ma), but they lacked cambium and it remains unclear how and when the first trees evolved. Progymnosperms faded and gymnosperms arose during Middle Carboniferous, and conifers, ginkgos, cycads, tree ferns and cordaites were well established by the Carboniferous–Permian transition (299 Ma). Woods of the earliest conifers were different from those of today, and not until Late Triassic (220 Ma) did any begin producing secondary xylem similar to modern woods, the xylem phenotypes of Cupressaceae and Araucariaceae emerging much earlier than those of Pinaceae and flowering plants. Conifers have persisted and done relatively well despite major extinction events, severe climate change, insectivory, herbivory and microbial activity, all of which were in effect before as well as during the appearance of trees on Earth. Approximately 600 conifer species continue to exist, and the survivors presumably possess the physiological fitness needed to adapt to an ever-changing biosphere. However, this is speculative because their physiology remains less than well understood. Forestry interventions such as planting one species to the exclusion of others have the potential to exacerbate as well as sustain the ongoing existence of our remaining conifers. Key words: bordered pit, cambium, cell biology, cellulose, evolution, lignin, paleobotany, protoplasmic autolysis, secondary growth, wood formation, xylogenesis

Xylary union between elongating lateral branches and the main stem in Populus deltoides

1983 ◽  
Vol 61 (4) ◽  
pp. 1040-1051 ◽  
Author(s):  
Philip R. Larson ◽  
David G. Fisher
Keyword(s):  
Populus Deltoides ◽  
Secondary Xylem ◽  
Cambial Activity ◽  
Main Axis ◽  
Main Stem ◽  
Leaf Trace ◽  
Primary Xylem ◽  
Lateral Bud ◽  
Lateral Branches ◽  
Secondary Vessels

The vasculature of elongating lateral branches was examined to determine how vessels produced in the branch unite with those produced in the main stem axis to form a continuous transport system. In a previous study it was found that differentiation of both primary and secondary xylem in a lateral bud or branch is independent of that in the main axis; i.e., xylem does not differentiate into the bud or branch from the main axis. When serial sections of the nodal region are followed downward, the bud vascular cylinder merges with that of the main axis and the adaxially situated bud traces (those nearest the stem) enter the bud gap margin first. The primary vessels of these bud traces differentiate in an oblique downward path along the margins of the bud gap, and they form radial files of primary vessels that lie adjacent to primary xylem of leaf traces in the stem. Traces situated more abaxially in the bud (those farther from the stem) contribute to other radial files of primary vessels, each of which lies progressively closer to the bud gap. Secondary xylem is initiated in the stem before it is in the branch. Consequently, the last-formed metaxylem vessels of the bud traces are continuous with secondary vessels of the stem. These latter vessels lie in the stem secondary xylem immediately external to primary xylem from the bud. Secondary xylem in the branch is initiated when foliage leaves and internodes mature. Secondary vessels formed in the branch traces are continuous with secondary vessels in the stem; these vessels are embedded in a matrix of fibers. Because cambial activity is more vigorous in the stem than in the branch, two vessels that are radially adjacent in the branch may be widely separated by fibers in the stem. The central trace of the axillant leaf enters the gap immediately below the last branch traces; at this level in the stem the leaf trace vasculature is entirely primary. The stem secondary xylem that overlies the leaf trace is continuous with that in the axillary branch.

scholarly journals Analysis of anatomical and functional traits of xylem in Humulus lupulus L. stems

2011 ◽  
Vol 57 (No. 7) ◽  
pp. 338-343 ◽  
Author(s):  
V. Gloser ◽  
M. Baláž ◽  
P. Svoboda
Keyword(s):  
Hydraulic Conductivity ◽  
Secondary Xylem ◽  
Structure And Function ◽  
Simplified Approach ◽  
Primary Xylem ◽  
Humulus Lupulus L ◽  
Mean Diameter ◽  
Well Differentiated ◽  
And Function ◽  
Stem Segments

Hop plants have unusually low values of the ratio between internal area of xylem conducts and leaf area, indicating that their xylem conducts solutes very efficiently. In the present study we analyzed the structure and function of xylem in stems of field-grown hop plants. Vessels of secondary xylem (SX) were more potent to conduct solutes compared to primary xylem (PRX) as they were wider (maximal/mean diameter of SX vessels in basal stem segments was on average 209/73 μm compared to 82/40 μm in PRX) and longer (up to 75 cm, compared up to 30 cm in PRX). The contribution of PRX to total Kh of the segment was on average 45.0 ± 29.9% in apical, but only 1.8 ± 0.4% in basal stem segments with well differentiated SX. We discuss differences and non-linear relationship between measured hydraulic conductivity (Kh) and Kh calculated from vessel diameters and suggest a simplified approach suitable for routine evaluation of theoretical Kh of hop cultivars.

scholarly journals Vincetoxicum indicum (Burm.f.) Mabb. - a case of transient abnormal secondary thickening in stem

2021 ◽  
Vol 13 (2) ◽  
pp. 10872
Author(s):  
Mammen DANIEL ◽  
Denni MAMMEN
Keyword(s):  
Medicinal Plant ◽  
Secondary Xylem ◽  
The Other ◽  
Abnormal Behaviour ◽  
Tylophora Indica ◽  
Primary Xylem ◽  
Complete Ring ◽  
Secondary Thickening ◽  
Two Sides

Vincetoxicum indicum (Burm.f.) Mabb. (Syn. Tylophora indica (Burm.f.) Merr., T. asthmatica W. &A.), an important twining medicinal plant of India, was found to show a transient anomalous secondary thickening to facilitate the twisting of stem around a support. The very young stem had a continuous primary xylem cylinder, the protoxylem of which differentiated to two large bundles on the opposing sides and many smaller bundles in between. In the initial stages of maturation, the cambium outside the two large protoxylem groups behaved abnormally in producing more phloem outwards and little or no secondary xylem inwards to produce two wedge shaped phloem groups on opposite sides. The production of crescent shaped secondary xylem on the other two sides which fell at a right-angled plane resulted in bulging of these sides away from the anomalous cambium to create a rectangular stem having two broad sides which were used as the facing sides of stem against a support. As soon as the twisting nature was established, the anomaly was reversed and the anomalous cambial patches started behaving normally to produce a complete ring of secondary xylem. As this abnormal behaviour happened only during the twisting of stem, this is considered as an adaptational anomalous secondary thickening. 

scholarly journals Sommerxylon spiralosus from Upper Triassic in southernmost Paraná Basin (Brazil): a new taxon with taxacean affinity

2004 ◽  
Vol 76 (3) ◽  
pp. 595-609 ◽  
Author(s):  
Etiene F. Pires ◽  
Margot Guerra-Sommer
Keyword(s):  
Northern Hemisphere ◽  
Secondary Xylem ◽  
Upper Triassic ◽  
New Taxon ◽  
Axial Parenchyma ◽  
Primary Xylem ◽  
Bordered Pits ◽  
The Family ◽  
Paraná Basin ◽  
Parana Basin

The anatoical description of silici?ed Gymnospermae woods from Upper Triassic sequences of southernmost Paraná Basin (Brazil) has allowed the identi?cation of a new taxon: Sommerxylon spiralosus n.gen. et n.sp. Diagnostic parameters, such as heterocellular medulla composed of parenchymatous and sclerenchymatous cells, primary xylem endarch, secondary xylem with dominant uniseriate bordered pits, spiral thickenings in the radial walls of tracheids, medullar rays homocellular, absence of resiniferous canals and axial parenchyma, indicate its relationship with the family Taxaceae, reporting on the first recognition of this group in the Triassic on Southern Pangea. This evidence supports the hypothesis that the Taxaceae at the Mesozoic were not con?ned to the Northern Hemisphere.

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