Radial Walls Of Tracheids Research Articles

New investigations on Cretaceous woods from the Jiaolai Basin, Shandong Province and their palaeoclimate relevance

The Jiaolai Basin of China is the southernmost edge of the distribution of the northern Jehol Biota and an important area which bears both the northern and southern palaeogeographical fauna representative species. The Laiyang flora in the Jiaolai Basin is located in the transitional region between the Early Cretaceous southern and northern flora of China. Currently, research on the plants in the transitional region between the northern and southern flora are relatively weak. Our study of specimens has enriched our understanding of the floral landscape in the transitional region between the north and south flora. Cretaceous wood fossils are well preserved in China and 66 species of 29 genera have been reported up to now, which are widely distributed in China. However, in the Cretaceous Shandong Province, there are few records of wood fossils. So far, only one genus and two species have been reported. In this paper a new material of fossil wood is described from the Early Cretaceous Zhifengzhuang Formation of Laiyang Group in Jingzhi area of Anqiu City, Jiaolai Basin, Shandong Province. The present specimen has uniseriate to triseriate pits on the radial walls of tracheids, taxodioid cross-field pitting and other characters. This discovery contributes to a better understanding of fossil wood diversity in Jiaolai Basin during the Cretaceous. Through the well preserved growth rings of the specimens, it can be inferred that the environmental paleoclimate of the Early Cretaceous in Shandong Province was generally arid, with some areas being humid.

<i>XENOXYLON</i> (CONIFERALES) FOSSIL WOODS FROM THE LOWER CRETACEOUS DEPOSITS OF THE FRANZ JOSEF LAND ARCHIPELAGO

Fossil wood species Xenoxylon phyllocladoides and X. jakutiense of the Mesozoic genus Xenoxylon (Coniferales) are described from the Lower Cretaceous volcano-sedimentary deposits of Mac-Cult and Salisbury islands of the Franz Josef Land Archipelago. Fossil woods from Mac-Cult and Salisbury islands are described for the first time. Record of X. jakutiense from Salisbury Island represents the first record of this species from the island part of the Arctic. The presence of abietinean pitting on the radial walls of tracheids indicates that these species belong to the “phyllocladoides” group sensu Philippe et al. (2013), evolved from ancestral forms of Xenoxylon in the Early Jurassic. The discovery of X. phyllocladoides and X. jakutiense fossil woods in the Lower Cretaceous deposits both on the island and mainland parts of the Russian Arctic confirms the conclusions about floristic links between Franz Josef Land and the northern part of the Siberian Platform in the Early Cretaceous.

Two new petrified gymnosperms with solenoid piths from the Pedra de Fogo Formation, Permian of Maranhão, Brazil

Solenoid piths are formed by systems of secretory ducts or canals, and they are relatively common in petrified gymnosperms from the Permian of Gondwana. We described herein two new taxa, Polycanaloxylon merlottii gen. et sp. nov. and Europoxylon garapensis sp. nov., from the Pedra de Fogo Formation (Cisuralian), northeastern Brazil. In both species the pith is non-septate and solenoid, primary xylem bundles have endarch maturation, rays are short and uniseriate, pits on the radial walls of tracheids are commonly uni to biseriate, cross-field pitting is cupressoid and wood is pycnoxylic. Whereas P. merlottii has a solenoid pith with a parenchyma sheath and sclerenchyma cells, E. garapensis is distinguished by a pith that only has secretory canals and parenchyma cells. In addition to expanding the distribution area of a typical Euramerican taxon into Parnaíba Basin, the report of Europoxylon reinforces a connection between these areas in the Late Pennsylvanian, thus enabling the dispersion of floristic elements. Solenoid forms are especially common in Kungurian sedimentary deposits of southern Brazil, and possibly India. However, since the occurrence of them seems to be linked to specific habitats, it should be proven that such environments are indeed contemporaneous in order to use these stems as a tool for relative dating in Gondwanan localities.

Megaporoxylon sinensis sp. nov., a new coniferous trunk from the Upper Triassic of northern Bogda Mountains, northwestern China

A coniferous trunk, Megaporoxylon sinensis sp. nov., is described from the Carnian–Norian (Triassic) Huangshanjie Formation in the Dalongkou section, Jimsar County, Xinjiang, northwestern China. The trunk is composed of pith, primary and secondary xylem. The pith is solid, circular, heterocellular, with pitted parenchyma and secretory cells and canals. The primary xylem is endarch, with spiral and scalariform thickenings on tracheidal walls. The secondary xylem is pycnoxylic, consisting of tracheids and rays. Radial tracheidal pitting is araucarian. Tangential pitting and axial parenchyma are absent. Uniseriate pits with oval apertures are commonly present on radial tracheid walls. Biseriate pitting occurs only on radial walls of the first to fifth tracheids outward the primary xylem. Rays are parenchymatous, uniseriate, and 1–7 cells high. Cross-field pitting is window-like or phyllocladoid. Previous records of species of Megaporoxylon Kräusel were limited to the Southern Hemisphere during the Carboniferous to Triassic. Its occurrence from the Upper Triassic of northern Xinjiang is the first report in the Northern Hemisphere and suggests a floristic exchange between Gondwana and Laurasia. The new trunk and two previously described fossil stems, including Medulloprotaxodioxylon triassicum Wan et al. and Xenoxylon junggarensis Wan et al., demonstrate that conifers were important elements of Carnian–Norian terrestrial ecosystems and had a higher diversity in northern China than previous thought. The growth ring pattern of the trunk and palaeogeographic reconstruction of the research area at high latitudes suggest that the growth of the trees was limited by the seasonality of the light regime.

The first report of Lesbosoxylon Süss & Velitzelos from the early-middle Miocene of eastern Anatolia

A new fossil pine species from eastern Turkey is described and its botanical affinities are discussed. The sample was collected from the city of Kemaliye, Erzincan province, Turkey, and derives from the early-middle Miocene Divriği formation. Transverse, tangential and radial sections were taken from the petrified wood, and its palaeoxylotomical features were investigated. Based on its anatomical features including idioblastic cells in rays a new fossil-species of the genus Lesbosoxylon Süss & Velitzelos was identified as Lesbosoxylon kemaliyensis Akkemik & Mantzouka, sp. nov. Diagnostic features of the new species are: Transition from earlywood to latewood mostly gradual; axial and radial resin canals with thin-walled epithelial cells present; latewood tracheids thin to thick walled; bordered pits on radial walls of tracheids 1-2(-3) seriate; crassulae common; rays heterocellular, uniseriate, partly biseriate; uniseriate rays up to 27 cells high; fusiform rays up to 30 cells high; axial parenchyma occasionally present; ray tracheids 2-3 rows; cell walls of ray tracheids smooth; cross-field pitting pinoid, 1-2(-6) pits per cross-field. Detailed investigation of the botanical affinities of the new fossil wood suggested that the most closely related modern species is Pinus canariensis C. Sm in Buch, a relict species from the Canary Islands.

Oldest Jurassic wood with Gondwanan affinities from the Middle Jurassic of Tibetan Plateau and its paleoclimatological and paleoecological significance

Jurassic flora of the Tibetan Plateau is poorly known, with limited fossil records. The paleobiogeography of terrestrial biota is, however, one of the major evidences to reconstruct the intricate paleogeography of an area. Well-preserved fossil wood is described from the Middle Jurassic Xiali Formation (Callovian) in the South Qiangtang terrane of the Tibetan Plateau, SW China. The wood specimen is a well-preserved secondary xylem without growth rings. Bordered pits on the radial tracheid walls are mostly uniseriate distant, locally contiguous. Cross-fields have 1–2 large oopores. A systematic study indicates that the current fossil wood represents a new species, Circoporoxylon tibetense sp. nov. This is the earliest Laurasian data for the genus Circoporoxylon, which has a Gondwanan origin and subsequently became common in Laurasia during the Cretaceous. The present new finding indicates that Circoporoxylon might have reached the Laurasia via a Tibetan terrane. The presence of fungal remains and wood rotting structures resembling the extant white-rot testifies for the plant–fungal interaction in the Callovian. The absence of growth rings in Circoporoxylon wood and the absence of gypsum layers in the South Qiangtang terrane, together with the widely occurrence of gypsum layers in the North Qiangtang terrane, suggests the South Qiangtang terrane might be wetter than the latter during the Callovian age. The paleogeomorphological highlands of Central Uplift were most likely the boundary between the two. This paleoclimate zonation implies that the Permian to Mesozoic megamonsoon of the supercontinent Pangaea might have terminated in the northern of Paleo-Tethys before the Callovian.

Protaxodioxylon from the Late Jurassic to Early Cretaceous Kota Formation, Pranhita-Godavari Basin, India

The xylotomy of the silicified wood from the Late Jurassic to Early Cretaceous Kota Formation of the Pranhita-Godavari Basin is studied and its systematic affinity is identified here. The wood is characterised by distinct growth rings with mixed pitting on radial tracheid walls, and taxodioid cross-field pits. The combination of the features observed in the present wood indicates that, it belongs to Protaxodioxylon of the taxodiaceous Cupressaceae s. l., as a new species Protaxodioxylon sahnii sp. nov. The comparison of wood with the modern representatives of the family suggests its relation with Taxodium. The present fossil wood with distinct growth rings characterised by their low percentage of latewood suggests that the growth conditions were favorable. The riparian habitat was inferred for the Protaxodioxylon sahnii sp. nov., based on sedimentological and other associated plant fossils. The vegetation in the study area is possibly favored by the influence of a subtropical climate with seasons, and by high levels of precipitation along the river banks.

Xuanweioxylon damogouense sp. nov., a gymnosperm stem from the Lopingian (late Permian) of southwestern China and its systematic and paleoecological implications

A new species of permineralized gymnosperm stem is described from volcaniclastic tuffs in Lopingian (late Permian) Xuanwei Formation from eastern Yunnan province, China. The stem comprises well-preserved tissues of the pith, primary and secondary xylem. Pith is divided into a thick-walled parenchymatous peripheral zone and an inner parenchymatous part. Primary xylem strands are numerous and indistinct with mesarch maturation. Secondary xylem is pycnoxylic with scalariform bordered pits on radial tracheid walls, with rays normally uniseriate or partly biseriate. Cross-field pits are mixed and including circular, elliptical and scalariform pitting. Comparisons indicate a close affinity with the contemporaneous plant Xuanweioxylon scalariforme, but differences with it lead to the erection of Xuanweioxylon damogouense sp. nov. We evaluate the systematic affinity of both species of Xuanweioxylon and conclude they represent conifers based on features of their wood anatomy. We consider the Xuanwei Formation includes at least four species of conifer, and show that X. damogouense possessed weak growth rings and false rings that suggest it grew in a climate with low seasonality and occasional periods of drought.

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.

A new occurrence of silicified wood from the Early Cretaceous (Berriasian) Kagbeni Formation of north central Nepal

During recent fieldwork a second occurrence of silicified wood has been discovered from the Early Cretaceous Kagbeni Formation of north central Nepal. The wood exhibits anatomical features which are well in accordance with Araucarioxylon nepalense described from another locality in the Kagbeni Formation near Kagbeni in the Thakkhola Valley in central Nepal. It is a pycnoxylic wood with mostly uniseriate and rarely biseriate bordered pits on radial tracheid walls. According to recent taxonomic opinions this type of wood should not be treated as Araucarioxylon, but as Agathoxylon Hartig. Thus, we propose the name Agathoxylon nepalense comb. nov. for this type of wood. The sandstones of the Kagbeni Formation have been interpreted as delta–deposits, with a major flow direction from the south. This suggests that the wood originated from the northern margin of Gondwana (i.e. the Indian Plate).

First record of Podocarpoid fossil wood in South China

A new species of fossil conifer wood, Podocarpoxylon donghuaiense sp. nov., is described from the late Eocene of Nadu Formation in Baise Basin of the Guangxi Province, South China. This fossil wood is characterized by distinct growth rings, circular to oval tracheids in cross section, 1–2-seriate opposite pits on radial tracheid walls, uniseriate (rarely biseriate) rays, smooth end walls of ray parenchyma cells, and the absence of resin ducts, suggesting its affinity to Podocarpaceae. The new species is distinctive from other Cenozoic woods ascribed to this family by the combination of distinctive growth rings, the absence of axial parenchyma, the occurrence of bordered pits on tangential tracheid walls, and the occurrence of 3–4 cuppressoid or taxodioid pits on cross-fields. This represents the first record of podocarpoid fossil wood in South China and provides fossil evidence for the early dispersal and diversification of Podocarpaceae in eastern Asia as well as for mild temperate seasonal climate in this region during the late Eocene.

New record of fossil wood Xenoxylon from the Late Triassic in the Sichuan Basin, southern China and its paleoclimatic implications

Fossil wood is one of the significant proxies for terrestrial paleoclimate and paleogeographical reconstruction in Earth history. Abundant and diversified Mesozoic fossil woods are well recorded in China; however, Triassic fossil wood is very scarce. Here, we report a new fossil wood from the Late Triassic Xujiahe Formation (Norian to Rhaetian) in Guangyuan of northern Sichuan Basin, southwestern China. The fossil wood material consists of two well-preserved specimens yielding secondary xylem with distinct growth rings. Bordered pits on the radial tracheid walls are mostly contiguous, biseriate alternate, locally uniseriate and strongly flattened. Cross-fields show a large window-like pore. This anatomy is typical for the important fossil wood morphogenus Xenoxylon Gothan, and, based on a novel combination of radial and cross-field pitting type and ray height, a new species, Xenoxylon guangyuanense sp. nov. is recognized. The finding of this new fossil wood taxon contributes to a better understanding of the yet poorly documented Xenoxylon early radiation during the Late Triassic, as well as of the origin of X. meisteri group, a peculiar endemic group which diversified in Far-East Asia from the Triassic to the Early Cretaceous. Xenoxylon is a paleobiogeographically significant genus, being bound to cooler and/or wetter climates of Northern Hemisphere throughout its Late Triassic–Late Cretaceous range. The occurrence of Xenoxylon in the Sichuan Basin of southern China may indicate a short-term cooling event, sandwiched within a period during which warm and wet climate conditions largely prevailed over lower latitude regions of the Northern Hemisphere. Such a cooling event in the Sichuan Basin which was located at a low paleolatitude on the eastern rim of Tethys may be in accordance in time with the temperature decline event in Norian–Rhaetian boundary uncovered by oxygen isotope (δ18O) record in Italy of the western rim of Tethys.

Wood decay of Xenoxylon yunnanensis Feng sp. nov. from the Middle Jurassic of Yunnan Province, China

Abstract A permineralised gymnosperm wood, Xenoxylon yunnanensis Feng sp. nov., is described from the Middle Jurassic Shaximiao Formation in Huize County, Yunnan Province, Southwest China. The pycnoxylic wood consists of thick-walled tracheids and thin-walled rays. It is characterised by uniseriate, contiguous, compressed bordered pits on the radial walls of tracheids, and one large simple pit in each cross-field. Growth rings exhibit narrow latewood. The mean sensitivity of analysis of 25 growth rings is 0.2, suggesting that a climate with abundant rainfall and weak seasonality could have prevailed in Yunnan, at least locally, during the Middle Jurassic. The outer portion of the wood is largely decayed, and shows poorly preserved cells lacking details. Decayed tracheids displaying various features, including removal of middle lamellae, separations of secondary walls, presence of thickened corners and appositions, are recognised as cell reactions to fungal activity. Irregularly distributed micro-cavities are formed by complete decomposition of tracheids and rays in the wood. Abundant fungal remains occurring in the wood generally consist of multiple branched hyphae. These fungal hyphae are either confined to individual cell lumens or extend through adjacent cells. Although the probable reproductive structure and typical clamp connection are very rarely observed with few septate hyphae, the affinities of these fungal hyphae are somewhat obscure. Nevertheless, our study sheds light on the palaeoecology of Middle Jurassic terrestrial ecosystems of Southwest China.

Xuanweioxylon scalariforme gen. et sp. nov.: Novel Permian coniferophyte stems with scalariform bordered pitting on secondary xylem tracheids

Fossil lignophyte stems show remarkable diversity including non-sympodial and sympodial forms and a variety of pith and tracheid structures. Most lack scalariform bordered pits on radial walls of secondary xylem tracheids, while these occur in the putative progymnosperm Protopitys and some (but not all) cycads, bennettitaleans, and angiosperms. We describe a new genus of Permian gymnosperms that comprises decorticated stems and branches with a parenchymatous pith that is septate in stems but entire in branches and has scleroid cells that are organised singly or in bands. Vasculature is non-sympodial, comprising endarch primary xylem strands that become mesarch leaf traces that are occluded through ontogeny. Secondary xylem is pycnoxylic with scalariform bordered pits on radial tracheid walls. The eustelic and non-sympodial organisation, the septate pith and the presence of scalariform bordered pits on secondary tracheids represent a unique combination of features not previously seen in lignophyte genera, justifying the erection of Xuanweioxylon scalariforme gen. et sp. nov. X. scalariforme shows similarities to several extinct and extant lignophytes but is placed within the coniferophytes — an informal grouping of conifer-like plants of uncertain affinity that includes probable sister groups to cordaitaleans and conifers. Scalariform bordered pitting in secondary tracheids is unique to Xuanweioxylon within coniferophytes, demonstrating previously unrecognised diversity within the group. Results suggest that coniferophytes include intermediates between cordaitaleans and conifers with other lignophytes including Protopitys, pteridosperms, cycads and Bennettitales.

First Record of Conifer Wood from the Cañadón Asfalto Formation (Early-Middle Jurassic), Chubut Province, Argentina

Abstract. A new fossil conifer wood —Brachyoxylon currumilii sp. nov.— is described from the Lower—Middle Jurassic of Chubut Province (Argentina). The specimens were collected at a locality where the Canadon Asfalto Formation is exposed, in the vicinity of the Cerro Condor village. The studied wood is characterized by mixed pitting in radial tracheid walls (predominantly uniseriate), araucarioid cross fields, low uniseriate rays and the absence of resin canals. The use of transmitted light and epifluorescence microscopy together with SEM imaging allowed the identification of additional characters such as the presence of pitting with torus-margo and compression wood. These characters are discussed in terms of their systematic relevance. On these grounds, the systematic affinity of the studied wood is discussed and linked to the extinct conifer family Cheirolepidiaceae, one of the dominant plant groups during the Jurassic and Cretaceous in Patagonia.

A Middle Devonian Callixylon (Archaeopteridales) from Ronquières, Belgium

A permineralized Callixylon trunk is reported from Ronquières, a mid to late Givetian (Middle Devonian) locality from Belgium. The specimen consists of an 80cm long trunk adpression whose central area is preserved as a pyrite permineralization. The pyritized area is composed of a eustele surrounded by secondary xylem. Tracheids show radially aligned groups of pits separated by unpitted regions on the radial walls of tracheids. The specimen belongs to a group of species characterized by a predominance of uniseriate rays and the lack of ray tracheids. This Callixylon specimen is one of the earliest representatives of the genus. It coexists at the locality with large cladoxylopsids and provides direct evidence that the tree habit had evolved in the archaeopteridalean progymnosperms by the Givetian.

Arthropod interactions with bennettitalean roots in a Triassic permineralized peat from Hopen, Svalbard Archipelago (Arctic)

Multiple thin-sections of a Late Triassic (Carnian) siliceous permineralized peat block likely derived from the De Geerdalen Formation on Hopen Island, Svalbard Archipelago, show a dense mass of roots preserving fine anatomical details of various stages of primary and secondary vascular tissue development. The presence of moderately defined rings with few latewood cells in the secondary xylem attests to growth in a seasonal environment. The presence of mucilage bodies and nests of sclerotic cells in the cortical tissues of the roots and pith of subaerial stem fragments, together with scalariform pitting on radial tracheid walls and 2–12 simple pits per cross-field favor bennettitalean affinities for the roots. Evidence of a rich fauna of detritivores inhabiting the peat profile is represented in the form of extensive damage to cortical tissues of dead roots and abundant coprolites preserved both within chambers excavated in the plant tissues and in the peat matrix. Less common gall-like structures within the roots indicate the presence of parasitic organisms in the palaeo-peat ecosystem.

Cycad Wood from the Lopingian (Late Permian) of Southern China:Shuichengoxylon tianiigen. et sp. nov.

AbstractAnatomically preserved wood collected from coal seam no. 1 of the Naluozhai coal mine in the Lopingian (Late Permian) Wangjiazhai Formation in western Guizhou Province, China, is documented and interpreted. The wood belonged to a trunk with an inferred diameter of 25 cm or more and consists of axial tracheids and horizontal rays. Tracheids vary greatly in size, and small ones are usually irregularly arranged. Tracheid walls are 5–10 μm thick and usually bilayered. There are usually biseriate araucarioides-type bordered pits on the radial tracheid walls. Two to five oval bordered pits are in each cross-field. Ray cells are thin walled, although thick-walled cells exist in some rays. Rays are quite variable in width and height. Uni- and partly biseriate rays are usually 2–20 cells high, while bi- and partly tri- to tetraseriate ones are 5–79 cells high. The cell size of rays is also quite variable and is usually larger than that of tracheids in the tangential direction. There are numerous leaf trace...

A unique gymnosperm from the latest Permian of China, and its ecophysiological implications

A unique coniferous woody stem Shenoxylon mirabile gen. nov. et sp. nov. is described from the very late Late Permian Changhsingian (Lopingian) Sunjiagou Formation of the Shitanjing coalfield, northern China. The silicified decorticated stem is characterized by a complex pith in the broad (7 mm) eustelic vascular system, thick secondary xylem cylinder and helically arranged leaf traces. The heterogeneous pith consists of a densely arranged sclerified intramedullary sheath that separates the loosely arranged central parenchyma and peripheral sclerified cells into three prominent zones. The primary xylem strands show endarch maturation, the tracheids from the protoxylem to metaxylem showing annular to scalariform/reticulate thickenings. The secondary xylem is pycnoxylic; uniseriate bordered pits are continuous or individually spaced on the radial walls of tracheids, with partially biseriate, alternate or occasionally opposite; the cross-fields show one or two cupressoid pits; ray cells are parenchymatous with smooth walls; axial parenchyma is developed. Growth-rings are present and false rings are frequently developed throughout the secondary xylem; resin canals are absent. The leaf traces are composed of monarch vascular bundles and of circular to longitudinally elongate shape in cross section; they originate from the periphery of the pith and pass through the whole xylem cylinder nearly horizontally. The frequent occurrences of false rings are interpreted as ecophysiological responses of the plant to the environmental turbulences during the latest Permian terrestrial ecosystem.

Xylem anisotropy and water transport--a model for the double sawcut experiment

Early experiments with overlapping cuts to the stems of trees demonstrated that lateral flow within the stem must be possible to allow such trees to maintain water flow to their leaves. We present a mathematical approach to considering lateral flow in stems by treating the xylem as an anisotropic medium for flow and develop an expression of its conductivity in the form of a tensor. In both 3D models of tracheid-bearing stems with cuts (incorporating this tensor analysis) and experimental stems with steadily deepening cuts, it is shown that flow can continue despite the presence of even strongly overlapping cuts through 90% of the stem. Such remaining conducting ability was, however, strongly dependent on values for radial and tangential conductivity (conductivity to lateral flow across the stem either radially with respect to the central axis or tangentially to the stem surface). Furthermore, the lateral flow around obstructing cuts was more dependent on tangential flow around the stem upstream and downstream of the cuts than on radial flow across the stem. The relative importance of tangential flow could be accounted for by a greater tangential conductivity, perhaps related to the predominance of pits on radial walls of tracheids, and the presence of non-conducting pith and early growth rings in the stems. These results demonstrate that a consideration of anisotropy in transport properties of the xylem will be important for future studies of flow in stems around naturally occurring geometric features such as branching points.