Carinal Canals Research Articles

Permineralized Calamitean Axes from the Upper Permian of Xinjiang, Northwest China and Its Paleoecological Implication

Two anatomically preserved calamitean axes are reported for the first time from the Late Permian Wutonggou Formation in the southern Bogda Mountains, Xinjiang Uygur Autonomous Region, Northwest China. Based on the anatomical features, these axes are assigned to Arthropitys. A new species Arthropitys taoshuyuanensis sp. nov. is established. A. taoshuyuanensis sp. nov. possesses a large pith and comprises large pith cavity and a narrow perimedullary zone at the nodes and diaphragms at the internodes. Carinal canals are circular and surrounded by a single layer of metaxylem tracheids. Secondary xylem is divided into interfascicular rays and fascicular wedges. Interfascicular rays are initially four to five cells wide and taper abruptly centrifugally. Fascicular wedge consists of thick-walled tracheids and thin-walled fascicular ray cells. Radial tracheid walls have uniseriate or biseriate circular pits, or scalariform pits. The absence of growth rings in the Arthropitys specimens indicates that they probably lived in the wetland area under stable annual temperature and water sufficient conditions.

Extracellular ice management in the frost hardy horsetail Equisetum hyemale L.

Formation of extracellular ice at specific positions in the plant interior is a common and probably essential component of plant cold hardiness. Studies on extracellular freezing in spore-bearing plants are, however, scarce. In this study, extracellular ice formation in the cold hardy horsetail Equisetum hyemale L. is analyzed. Horsetails show an extensive system of intercellular air spaces which are probably crucial for internal ice storage during winter. Previous studies emphasized the spacious pith cavity as the main place for ice crystal growth. Shoots were studied during summer and in the frozen state in winter, after natural acclimatization, by using digital (incident light) microscopy, Scanning Electron Microscopy and Cryo Scanning Electron Microscopy. It was shown that the vallecular canals also contain a large share of ice bodies under freezing conditions. The vallecular canals, which are directly seated within the cortex and whose interior is directly connected to the cortex via gaps in the canal wall, were often and rapidly filled with ice. The pith cavity also contained ice, depending on the position along the shoot and the internode. The carinal canals contained almost no ice crystals. Furthermore, some ice crystals were detected in the intercellular spaces of the chlorenchyma and the substomatal chamber. The stomatal antechamber, however, was always ice-free, probably due to the presence of water-repellent wax crystals. The results of this study support available evidence for the crucial role of pre-existing extensive lacunae for extracellular ice formation in E. hyemale. Furthermore, the findings indicate that anatomical details of canal structure and position are important for the pattern of extracellular ice accumulation.

Equisetum

Equisetum

An extensin-rich matrix lines the carinal canals in Equisetum ramosissimum, which may function as water-conducting channels.

The anatomy of Equisetum stems is characterized by the occurrence of vallecular and carinal canals. Previous studies on the carinal canals in several Equisetum species suggest that they convey water from one node to another. Cell wall composition and ultrastructure have been studied using immunocytochemistry and electron microscopy, respectively. Serial sectioning and X-ray computed tomography were employed to examine the internode-node-internode transition of Equisetum ramosissimum. The distribution of the LM1 and JIM20 extensin epitopes is restricted to the lining of carinal canals. The monoclonal antibodies JIM5 and LM19 directed against homogalacturonan with a low degree of methyl esterification and the CBM3a probe recognizing crystalline cellulose also bound to this lining. The xyloglucan epitopes recognized by LM15 and CCRC-M1 were only detected in this lining after pectate lyase treatment. The carinal canals, connecting consecutive rings of nodal xylem, are formed by the disruption and dissolution of protoxylem elements during elongation of the internodes. Their inner surface appears smooth compared with that of vallecular canals. The carinal canals in E. ramosissimum have a distinctive lining containing pectic homogalacturonan, cellulose, xyloglucan and extensin. These canals might function as water-conducting channels which would be especially important during the elongation of the internodes when protoxylem is disrupted and the metaxylem is not yet differentiated. How the molecularly distinct lining relates to the proposed water-conducting function of the carinal canals requires further study. Efforts to elucidate the spatial and temporal distribution of cell wall polymers in a taxonomically broad range of plants will probably provide more insight into the structural-functional relationships of individual cell wall components or of specific configurations of cell wall polymers.

Equisetum Xylem: SEM Studies and their Implications

Abstract Scanning electron microscope (SEM) studies of xylem of three species of Equisetum reveal numerous details not previously reported on the basis of light microscopy. SEM images of thick (ca. 1 mm) sections reveal pit shapes, cell contexts, and microstructure of pit membranes. Pit shapes are remarkably diverse in comparison to those of ferns or conifers. Nodal tracheary elements are isodiametric to fusiform in shape, and have crowded circular (mostly) to elongate prominently bordered pits and uniformly thick secondary walls. Internodal tracheary elements, by contrast, have relatively large circular pits with inconspicuous borders. Secondary walls of internodal tracheids are thin, with thickenings that are annular, looplike, or of some intermediate form. Metaxylem internodal tracheary elements line the inner surface of carinal canals ( = proxylem lacunae), and many of the large circular (often crateriform) pits facing the canals may lack pit membranes, especially in E. giganteum and E. myriochaetum....

Phylogenetic diversification of Equisetum (Equisetales) as inferred from Lower Cretaceous species of British Columbia, Canada

Three types of anatomically preserved vegetative shoots with features that characterize crown group Equisetum have been discovered in Lower Cretaceous deposits (≈136 Ma) of British Columbia, Canada, suggesting the genus is much older than currently believed. Specimens include two types of aerial shoots described as E. haukeanum sp. nov. and E. vancouverense sp. nov. and one type of subterranean rhizome. Shoots are 1-2 mm in diameter, jointed, and in cross section have fluted stems with a hollow pith. Distinctive patterns of cortical sclerenchyma and different ridge morphologies characterize each shoot morphotype. Nodes display irregular branching, highly fused leaf sheaths, and a nodal diaphragm. The aerial stem morphospecies have vallecular canals on alternating radii with carinal canals of an equisetostele surrounded by only a few tracheids. No secondary tissues are produced. Bands of surficial stomata flank the furrows of one morphospecies. Rhizomes and aerial shoots are of a similar size, suggesting that the plants were equivalent in stature to the smallest living Equisetum species. These fossils augment our understanding of evolutionary transformations that led from Paleozoic Archaeocalamitaceae and Calamitaceae to crown group Equisetaceae, suggesting that the initial diversification of Equisetum began far earlier than suggested by molecular-clock-based estimates.

Development and ecological implications of dormant buds in the high‐Paleolaltitude Triassic sphenophyte Spaciinodum (Equisetaceae)

Spaciinodum collinsonii, a Triassic sphenophyte from the central Transantarctic Mountains, Antarctica, is reinterpreted based on new material in order to clarify discrepancies from previous work and to detail the development and ecology of the Spaciinodum plant. Vegetative stems have alternating nodes and internodes, nodes distinguished by a solid diaphragm of tissue, internodes by the presence of vallecular (cortical) and carinal canals, and a hollow pith. Whorls of branches arise immediately above the nodes, alternating with the leaves of the subjacent nodes. Branches develop in the cortex and are anatomically similar to the stems. While Spaciinodum is similar to extant Equisetum, it is distinctive in that its large vallecular canals form a complete ring within the cortex and are separated only by thin fimbrils of tissue. The majority of specimens of Spaciinodum are now believed to be dormant buds with condensed nodes and internodes, with progressively longer internodal regions more basally. More apical portions of buds have cellular internodes because the areas where the canals will form have not yet ruptured from elongation. The abundance of buds and the absence of elongated stems in the permineralized peat deposit suggest that Spaciinodum underwent dormancy during the dark Antarctic winters.

Un nuevo tallo permineralizado de Equisetales de la Formación Los Rastros (Triásico Medio - Superior), provincia de San Juan, Argentina

A new permineralized Equisetalean stem from Los Rastros Formation (Middle-Upper Triassic) from San Juan province, Argentina. Several stems remains of a new genus and species belonging to the order Equisetales are described. They are represented by ribbed stems with distinct nodes and internodes, a pith with some sclerenchymatic cells and carinal canals. Wedge-shaped primary xylem and fascicular wedges of secondary xylem alternating with uniseriate rays are preserved. Comparison of these stems with other Equisetalean fossils from Gondwana is difficult because of their different kinds of preservation. There are only few records of permineralized Equisetalean stems from the Gondwana Triassic because the majority of data are derived from compression-impression fossils; however, one of them, Spaciinodum Osborn & Taylor, from Antarctica, is also based on a permineralization. The anatomical structure of the studied material suggests that it is a new taxon, as their features differ from all previously known species.

A large anatomically preserved calamitean stem from the Upper Permian of southwest China and its implications for calamitean development and functional anatomy

A large permineralized calamitean stem, Arthropitys yunnanensis Tian et Gu from the Upper Permian of southwest China is reinvestigated and interpreted. The stem has a broad pith and well developed and large carinal canals. Secondary xylem is thick and characterized by wide parenchymatous interfascicular zones that remain constant in width throughout the wood. Striking features of the stem include the abundant leaf traces arranged in two whorls in the cortex with this arrangement previously unrecognized within calamitean stems, and the presence of growth rings in secondary xylem that suggest frequent fluctuations in environmental stress presumably due to variations in water availability. Features of A. yunnanensis infer the stem to be in the epidogenetical phase of calamitean development, and suggest it to be the basal part of a large trunk. Comparisons with biomechanical models for calamitean stems suggest this species had a semi-self supporting habit.

Unusual Metaxylem Tracheids in Petioles of Amorphophallus (Araceae) Giant Leaves

Petioles of huge solitary leaves of mature plants of Amorphophallus resemble tree trunks supporting an umbrella-like crown. Since they may be 4 m tall, adaptations to water transport in the petioles are as important as adaptations to mechanical support of lamina. The petiole is a cylindrical shell composed of compact unlignified tissue with a honeycomb aerenchymatous core. In both parts numerous vascular bundles occur, which are unique because of the scarcity of lignified elements. In the xylemic part of each bundle there is a characteristic canal with unlignified walls. The xylem pecularities are described and interpreted. Vascular bundles in mature petioles of Amorphophallus titanum and A. gigas plants were studied using light and scanning electron microscopy. The xylemic canal represents a file of huge metaxylem tracheids (diameter 55-200 microm, length >30 mm) with unlignified lateral walls surrounded by turgid parenchyma cells. Only their end walls, orientated steeply, have lignified secondary thickenings. The file is accompanied by a strand of narrow tracheids with lignified bar-type secondary walls, which come into direct contact with the wide tracheid in many places along its length. The metaxylem tracheids in A. petioles are probably the longest and widest tracheids known. Only their end walls have lignified secondary thickenings. Tracheids are long due to enormous intercalary elongation and wide due to a transverse growth mechanism similar to that underlying formation of aerenchyma cavities. The lack of lignin in lateral walls shifts the function of 'pipe walls' to the turgid parenchyma paving the tracheid. The analogy to carinal canals of Equisetum, as well as other protoxylem lacunas is discussed. The stiff partitions between the long and wide tracheids are interpreted as structures similar to the end walls in vessels.

A new species of the sphenopsid stem Arthropitys from Late Permian volcaniclastic sediments of China

Anatomically preserved calamitean stems are described from a previously unknown Late Permian locality in Sichuan Province, China, where they are preserved in volcaniclastic tuffs. Stems possess a large pith with secretory cells and pith cavity, and a narrow perimedullary zone. Primary xylem strands have poorly developed carinal canals whereas the secondary xylem is divided into parenchymatous interfascicular zones and fascicular wedges of tracheids and secondary rays, with the tracheids of the inner part of the secondary xylem having nearly the same size and shape with the interfascicular rays. Interfascicular rays taper abruptly centrifugally. Tracheids of the secondary xylem have scalariform thickenings and cross-fields possess oval–elongate scalariform pits. Secondary rays are parenchymatous and narrow, usually uni- to biseriate and less frequently organized in three to four seriates. The cortex is divided into an inner and outer zone, and primary xylem strands alternate at the nodal region. These stems conform to the features of the genus Arthropitys Geoppert and are most similar to Arthropitys lineata from the Early Permian of Europe; they also are similar to Arthropitys communis and Arthropitys hirmeri var. intermedia from Late Carboniferous coal balls in Europe and North America. However, the Chinese specimens are distinct in a number of ways including characters of the cells surrounding the carinal canals, the carinal canals themselves, features of the secondary xylem and also in their tracheid morphology, leading to the creation of a new species, Arthropitys junlianensis sp. nov. Implications of A. junlianensis on sphenopsid taxonomy, phylogeny and distribution are discussed, and the nearly identical morphology of this new sphenopsid to those of the Late Paleozoic coal swamps of Europe and North America is considered.

Non invasive imaging of water flow in plants by NMR microscopy

Water flow in the stems of the horsetailEquisetum hyemale, the flowering plantStachys sylvatica and the mossDendroligotrichum dendroides was observed non-invasively using NMR microscopy. A Pulsed Gradient Spin Echo sequence using a single phase encoding step was used. We demonstrate by this method that water flow inEquisetum occurs in the carinal canals and in the xylem vessels of the vascular tissue ofStachys and in the central water-onducting strand ofDendroligotrichum.

Structurally Preserved Sphenophytes from the Triassic of Antarctica: Vegetative Remains of Spaciinodum, gen. nov.

Sphenophyte remains of Early-Middle Triassic age are described from silicified peat collected in the Transantarctic Mountains of Antarctica. The new sphenophyte, Spaciinodum collinsonii sp. nov., is represented by ribbed, jointed stems with characteristic pith and carinal canals. Stems are relatively small, ranging from 1.8-3.0 mm in diameter, lack secondary tissues, and are characterized by vallecular canals that are restricted to nodal regions. The internodal vascular system consists of 12-18 collateral bundles which alternate between successive internodes. A complete vascular ring is present in the nodal region and is surrounded by a continuous double endodermis. Xylem is endarch and composed of elements ranging from annular to reticulate. The Antarctic sphenophyte is compared with other Gondwana fossil articulates and extant Equisetum. Superficial stomata suggest affinities with modern Equisetum subgenus Equisetum; however, some anatomical differences preclude assignment with living species.

STRUCTURALLY PRESERVED SPHENOPHYTES FROM THE TRIASSIC OF ANTARCTICA: VEGETATIVE REMAINS OF SPACIINODUM, GEN. NOV.

Sphenophyte remains of Early‐Middle Triassic age are described from silicified peat collected in the Transantarctic Mountains of Antarctica. The new sphenophyte, Spaciinodum collinsonii sp. nov., is represented by ribbed, jointed stems with characteristic pith and carinal canals. Stems are relatively small, ranging from 1.8–3.0 mm in diameter, lack secondary tissues, and are characterized by vallecular canals that are restricted to nodal regions. The internodal vascular system consists of 12–18 collateral bundles which alternate between successive internodes. A complete vascular ring is present in the nodal region and is surrounded by a continuous double endodermis. Xylem is endarch and composed of elements ranging from annular to reticulate. The Antarctic sphenophyte is compared with other Gondwana fossil articulates and extant Equisetum. Superficial stomata suggest affinities with modern Equisetum subgenus Equisetum; however, some anatomical differences preclude assignment with living species.

EQUISETUM CLARNOI, A NEW SPECIES BASED ON PETRIFACTIONS FROM THE EOCENE OF OREGON

Equisetum clarnoi is described from four silicified stem fragments and numerous small roots from the Eocene Clarno Chert of Jefferson County, Oregon. Stems are up to 8.0 mm in diam and have sunken stomata arranged vertically in a single line flanking each of the external biangulate stem ridges, features that clearly ally this species with the subgenus Hippochaete. External stem ridges are equal in number to the carinal hypodermal bands. The hypodermis is composed of fibers and has prominent carinal bands up to 0.75 mm long and shorter vallecular bands. Cortical parenchyma cells enclose prominent vallecular canals which are lined by specialized thick‐walled parenchyma cells. The double, common endodermis has prominent casparian strips. Vascular bundles are composed of four to seven metaxylem tracheids flanking each side of the phloem and protoxylem tracheids which occur singly on the internal surface of the small carinal canals. Leaf sheaths in cross section have an adaxial fibrous layer and an external or near external fibrous bundle. Roots are up to 2.0 mm in diam and have paired cuboidal epidermal cells from which root hairs arise. The stele of the root is central and shows exarch primary xylem maturation. Equisetum clarnoi most closely resembles the extant Equisetum hyemale var. affine.

Equisetum clarnoi, a New Species Based on Petrifactions from the Eocene of Oregon

Equisetum clarnoi is described from four silicified stem fragments and numerous small roots from the Eocene Clarno Chert of Jefferson County, Oregon. Stems are up to 8.0 mm in diam and have sunken stomata arranged vertically in a single line flanking each of the external biangulate stem ridges, features that clearly ally this species with the subgenus Hippochaete. External stem ridges are equal in number to the carinal hypodermal bands. The hypodermis is composed of fibers and has prominent carinal bands up to 0.75 mm long and shorter vallecular bands. Cortical parenchyma cells enclose prominent vallecular canals which are lined by specialized thick-walled parenchyma cells. The double, common endodermis has prominent casparian strips. Vascular bundles are composed of four to seven metaxylem tracheids flanking each side of the phloem and protoxylem tracheids which occur singly on the internal surface of the small carinal canals. Leaf sheaths in cross section have an adaxial fibrous layer and an external or near external fibrous bundle. Roots are up to 2.0 mm in diam and have paired cuboidal epidermal cells from which root hairs arise. The stele of the root is central and shows exarch primary xylem maturation. Equisetum clarnoi most closely resembles the extant Equisetum hyemale var. affine.

Origin and Development of Tissues in Equisetum scirpoides

1. The first periclinal division in each segment from the apical cell of the stem separates pith and primary cortex, which in turn gives rise to stele and cortex. 2. The pericycle, endodermis, and one or two layers of the inner cortex of the stem are stelar in origin. 3. Evidence is presented for regarding the so-called inner endodermis of the root as pericycle. 4. The endodermis and pericycle of the root are of cortical origin. 5. Dormant branches occur as in other species of Equisetum. They are exogenous in origin. 6. The first root developed by the branch is endogenous. 7. The stelar parenchyma in the root is much reduced. 8. Hydathodes of the water stomata type occur on the upper surface of the leaves. 9. Rare but well-developed tyloses are found in the carinal canals. 10. Reduction in xylem is extreme, the supranodal wood being frequently absent above the leaf traces, forming a gap in the xylem. 11. The gaps in the xylem of the cone are correlated with the size of the stele and failure of the funda...

On the Occurrence of Cavity Parenchyma and Tyloses in Ferns.

Cavity parenchyma, though generally confined to the petiolar protoxylem areas in the Filicales, frequently occurs in similar areas in the rhizomes of Pteridium aquilinum. In this species it occurs chiefly in the outer ring of meristeles, and is only found occasionally in the inner system. It also occurs sometimes in the rhizome of Matonia pectinata An analogous type of parenchymatous ingrowth may be formed in the internodal carinal canals of the rhizome of Equisetum arvense as a result of wounding. True tyloses, resulting in the occlusion of the metaxylem, occur in wounded roots of Marattia fraxinea. These may become lignified. The evidence as to the nature of the growths occluding the metaxylem elements in the fossil fern Ankyropteris corrugata is reviewed, and is held to support the view that they are true tyloses. I should like to express my thanks to the Keeper of the Geological Department, British Museum, for permission to study the slides in the Williamson and Scott Collections; to Mr. W. N. Edwards, for many kindnesses whilst working at the British Museum; and to Professor F. E. Weiss and Professor F. W. Oliver, for the loan of slides of which they have charge. To Mr. J. Ramsbottom and Mr. F. T. Brooks I am indebted for information with regard to the behaviour of fungal hyphæ and also to the former for the Latin diagnosis of Halysiomyces.