Indistinct Growth Rings Research Articles

Qualitative Anatomical Characteristics and Fiber Quality of Tapped Styrax sumatrana Wood Grown in North Sumatra, Indonesia

This study investigated the qualitative anatomical characteristics and fiber quality of tapped Styrax sumatrana wood to facilitate its further utilization. The transverse surface of the tapped S. sumatrana was light or greyish brown in the sapwood and reddish brown in the heartwood. The resin canals of the tapped wood were formed along the growth rings at the boundaries between the heartwood and sapwood. Furthermore, microscopic analyses revealed an irregular outline and rounded epithelial cells at the edges of the intercellular traumatic canal (TC). Approximately 8–16 epithelial cells surrounded the resin canals. The fibers in the tapped S. sumatrana were generally thin-walled, whereas those near the TC were thick-walled. Moreover, S. sumatrana were diffuse-porous and exhibited intermediately distinct or indistinct growth ring boundaries. The vessels were mainly radial multiples and clusters of 3–5. In addition, they showed a diagonal-to-radial pattern arrangement and a few tangential bands. Deposits were observed in some vessels in the tapped part but were absent in the untapped part. The fiber length of the tapped S. sumatrana wood was classified as moderate to extensive and categorized as second-grade pulp quality. Finally, the cell walls were classified as thin to moderate.

New record of conifer wood Agathoxylon from the Upper Jurassic in the Sichuan Basin, southern China, and its palaeobiodiversity and palaeoclimatic significance

ABSTRACT Although abundant and diverse foliage fossils are well recorded in the Upper Triassic and Lower–Middle Jurassic of the Sichuan Basin in South China, the Upper Jurassic plant fossils are rarely documented due to extensively developed red beds in this basin. Decades ago, abundant fossil wood specimens were discovered from the Upper Jurassic Penglaizhen Formation in the Sichuan Basin. However, detailed investigations on the systematic palaeobotany of these wood fossils are very limited, which hinders further understanding of the terrestrial ecosystem and biota. Here, we describe anatomically well-preserved fossil wood specimens from the Penglaizhen Formation at Wangjiagou Village of Shehong City in the central Sichuan Province. These wood fossils exhibit Agathoxylon anatomy with usually uniseriate contiguous radial tracheid pitting and araucarioid cross-field pitting, representing a new record of Agathoxylon in the Sichuan Basin, and contribute to further understanding of the vegetation composition of the southern phytoprovince in China during the Late Jurassic. Independent palaeoclimatic evidence from leaf, pollen and sediments indicates that the Agathoxylon trees from Shehong area have grown under generally hot and semi-arid or arid environmental conditions, probably in habitats at the banks of rivers and lakes with locally abundant water supply, as indicated by the indistinct growth rings.

Quaternary petrified trunks from Kamphaeng Phet, Thailand: Implications for past climate and preservation

Petrified trunks in Mueang Kamphaeng Phet District, upper Central Thailand, were unearthed in Quaternary deposits on the western rim of the Ping River. The sediments consist mainly of semi-consolidated gravel, sand, silt, and clay, indicating that the woods were transported by the ancient Ping River. Macroscopic features revealed that preservation of these fossils (e.g., intercellular spaces, iron oxides, quartz crystals, colors, and weathering conditions) shared many similarities to some petrified trunks in Tak Province. We investigated both large (approx. 0.50–0.7m wide, at least 10–20 meters long) and small fragments of fossils for both wood anatomical features and mineralogy. Diffuse porosity with indistinct growth rings and wide vessels at low densities suggest a tropical lowland forest paleoenvironment. Parenchyma patterns are aliform to confluent, banded, and diffuse-in aggregate. At least four distinct types of wood were recognized from this site. Among them, three wood types originate from legume trees (Fabaceae), while the fourth is from a eudicotyledonous tree. Two of the three legumes show closest resemblance to a tall (canopy emergent) legume tree, Koompassia cf. malaccensis Maingay ex Benth. and one resembles the legume Koompassia cf. malaccensis or cf. Pahudioxylon bankurensis Chowdhury, Ghosh, et Kazmi. The other legume-like wood shows banded parenchyma. Petrified wood from Kamphaeng Phet is correlative with other Quaternary paleofloras found in Northern Thailand in both preservation and taxa. The past climate, as inferred according to the Köppen-Geiger classification, was possibly similar to modern-day tropical rainforests (Af) in southern Thailand, Malaysia, and Indonesia in contrast to the modern vegetation in Mueang District, Kamphaeng Phet that is a mixed deciduous and dry dipterocarp forest where the modern climate in the area is tropical wet and dry (Aw).

Comparative Microstructural Evaluation of Wood in Three Dominant Ziziphus Species of Desert Ecosystem (Cholistan), Pakistan

The present microstructural evaluation was carried out on the woods of three ethnobotanically important local fruit trees, namely, Ziziphus mauritiana Lam., Z. spina-christi (L.) Willd., and Z. nummularia (Burm.f.) Wight and Arn., of family Rhamnaceae from Cholistan Desert of Pakistan. Wood samples were sectioned with sliding sledge microtome to make permanent slides for observing different anatomical parameters under the light microscope. All selected species were observed to have diffuse‐porous wood with indistinct growth rings. The vessels were rounded in outline in all the species studied and found mostly solitary or in radial multiples of 2 in Ziziphus mauritiana and Z. nummularia, while in radial multiples of 2 to 5 in Z. spina-christi. The intervessel pits were scalariform to opposite. The rays were uniseriate in Ziziphus mauritiana, while mostly were biseriate in Ziziphus spina-christi. Simple perforation plates and diffuse, confluent, and vasicentric types of axial parenchyma were present in all the selected species. The fibers were thin‐walled and nonseptate. One‐way ANOVA followed by the Tukey test was conducted to observe different anatomical variations within selected species. Principal component analysis revealed correlations among studied anatomical parameters. The number of rays per mm was comparatively larger in Ziziphus nummularia, showing its greater susceptibility to wood‐deteriorating agents than in other selected species. The Runkel ratio indicated the selected species suitable for making paper.

Ontogeny of multiple variants in the stems of Phaseolus lunatus L. (Fabaceae)

Development of the cambial variant is characteristic to most of the climbing members of the Fabaceae and is considered as an alternative path to increase their stem diameter for efficient supply of minerals and photosynthate within limited stem diameter. These alternative forms of secondary growths are ascribed as an adaptive character to increase stem flexibility and most often they are found to be taxon-specific. In the present study, histological investigation on the main stems of Phaseolus lunatus L. (Fabaceae) showed multiple combinations of variant secondary growth like the formation of vascular cylinders external to the secondary phloem and proliferation of parenchyma (axial and ray) followed by the development of interxylary phloem, interxylary cambia (functionally regular and inverse) and ray cambia. The secondary xylem produced by regular cambium was diffuse-porous with indistinct growth rings and composed of an abundance of thin-walled unlignified parenchyma. With the increase in age, phloem rays underwent dilatation, subsequently became meristematic and formed oval to circular vascular cylinders/units with irregular orientation. Concomitantly, dedifferentiation xylem parenchyma not only formed small islands of interxylary phloem but also led to the origin of interxylary cambial segments that differentiated bidirectionally and deposited xylem and phloem having inverse, diagonal, tangential or radial orientations. Similar cell division activity was also observed in marginal xylem ray cells (ray cambium) that produced both the xylem and phloem on either side. All these cambial variants are described in detail and their possible significance in the climbing habit is discussed.

Stressing environmental conditions in the “petrified forest” from the Mata Sequence in the Triassic context of the Paraná Basin

This study deals with the Piscina Outcrop, a Rhaetic reddish conglomeratic sandstone containing silicified logs which corresponds to the Mata Sequence in the southernmost Brazilian Paraná Basin. We performed ground-penetrating radar (GPR) analysis and the results ratified previous sequence stratigraphy analysis indicating that these deposits correspond to architectural elements exclusively related with the filling processes of fluvial channels. The erosive unconformity identified at the boundary between the Mata Sequence and the underlying rock packages could represent a considerable depositional hiatus. The integration of the GPR results with sedimentological and paleovertebrate data from a nearby outcrop at slightly lower topographic level indicated that the layer with the fossil woods is superimposed through an erosive unconformity to the stratigraphic levels corresponding to the Hyperodapedon Assemblage Zone of Carnian age from the basal portion of the Candelária Sequence. The wood assemblage was composed exclusively of araucarian coniferous stems identified as Agathoxylon (cf. Agathoxylon). The wood growth patterns were mainly characterized by woods showing indistinct growth rings, with latewood mostly restricted to one cell in each ring, suggesting weak seasonality and short-term, periodic droughts. Rare specimens with absent growth rings were also present. Oscillations in growth ring width and the common occurrence of false rings were likely linked to plant exposure to climatic instability. Anatomical evidence pointed to active biochemical responses to intense and extensive biological attack of fungi and arthropods. The dominant presence of carbon in the elemental composition of a dark substance filling many tracheid lumens suggested a very likely affinity with polyphenol remnants in biochemical barriers. The set of wood signatures seems to be linked to regional stressing conditions rather than to the paleolatitudinal location when compared to other key South American basins during the Rhaetic. An allochthonous taphocoenosis is the most likely taphonomic interpretation for this wood assemblage. The logs were probably incorporated into the stream through the collapse of riparian areas and buried in the fluvial channel by high-energy flows after biotic and abiotic decay processes during lifetime and secondarily through exposition before entombment in a river channel.

ANATOMICAL INVESTIGATION OF FIVE GENERA THE LEAST-KNOWN TIMBER OF APOCYNACEAE AND THEIR POTENTIAL UTILIZATION

Doubtlessly, wood identification is critically important for a number of sectors, including government organizations, the wooden-based industry, museums, law enforcement, and scientists working in the fields of botany, ecology, forestry, and wood technology. Unfortunately, most wood species listed as “the least-known species” lack essential knowledge or even their anatomical feature and basic properties to promote their usage. This research aimed to investigate the anatomical characteristics and fiber quality of the least-known timber species of Apocynaceae family, which are authentic wood collection from Xylarium Bogoriense, namely , Ervatamia. sphaerocarpa, E. aurantiaca, Kopsia flavida, Lepiniopsis ternatensis, Plumeria acuminata, P. rubra, and Voacanga foetida. Wood samples have indistinct growth ring boundaries, diffuse-porous vessels in diagonal and/or radial pattern, vessels in radial multiples of 4 or more cells, simple perforation plate, alternate intervessel pits; distinct borders of vessel-ray pits, similar with those of intervessel pits in size and shape throughout the ray cell, and septate fibers with simple pits to minutely bordered pits which are common in radial and tangential walls. Based on the fiber length and the derived values of fiber dimension, some species are classified into Quality Class II and III, and the rest of them are classified into Quality Class II or III for pulp and paper manufacturing. Based on general characteristics, commonly Apocynaceae can be used as handicrafts raw material. Based on the fiber quality, some species which are classified into Quality Class II, are predicted to have potential as pulp and paper material with medium quality.

Qualitative anatomical characteristics of the virgin cork in Quercus variabilis grown in Korea

To provide information on the identification and quality evaluation of Q. variabilis virgin cork from Korea, the qualitative anatomical characteristics of the virgin cork were observed by optical and scanning electron microscopy and compared with those of Q. suber reproduction cork from Portugal. Q. variabilis showed a narrower growth ring than Q. suber. A dark-brown zone with sclereids was found only in Q. variabilis cork. The lenticular channel in Q. variabilis is larger than that in Q. suber. Q. variabilis virgin cork showed a distinct growth ring boundary and an abrupt transition from earlycork to latecork with a few rows of latecork cells. Q. suber reproduction cork showed an indistinct growth ring with a gradual transition from one to two rows of latecork cells. In the earlycork, Q. suber showed mild corrugation, while Q. variabilis displayed significant corrugation with collapsed and distorted cork cells. The lenticular channel in Q. variabilis virgin cork was surrounded by thick-walled cells filled with compact lenticular filling tissue. Q. suber reproduction cork had an opening with loose lenticular filling tissue surrounded by thick-walled cells. Prismatic crystals, thick-walled sclereid cells, and fiber-sclereids were found only in Q. variabilis. A few trabeculae were found in both cork samples.

Mixoxylon australe gen. et sp. nov., a unique homoxylous wood with non-angiosperm affinity from the Lower Cretaceous of Antarctica (Albian, James Ross Island)

AbstractA unique homoxylous wood is described from the Albian Lewis Hill Member of the Whisky Bay Formation on James Ross Island as Mixoxylon australe Chernomorets & Sakala, gen. et sp. nov. This fossil taxon shows an unusual combination of features in having indistinct growth rings with a significantly wider earlywood zone than latewood zone, tracheids with scalariform to araucarian pitting, exclusively uniseriate rays with distinctly pitted both tangential and horizontal walls and araucarioid to podocarpoid cross-field pits. Its characteristics are intermediate between Phoroxylon Sze and Sahnioxylon Bose & Sah, so a new genus is proposed. Its systematic affinities are dubious, but it represents the southernmost evidence of the homoxylous Mesozoic wood with scalariform pitting described so far.

Anatomy of stem and root of Ipomoea cairica (L.) Sweet (Convolvulaceae) - the Lianescent Vascular Syndrome

Anatomy of stem and root of Ipomoea cairica (L.) Sweet (Convolvulaceae) - the Lianescent Vascular Syndrome. Among the Ipomoea species of economic importance, the liana Ipomoea cairica stands out because of its great pharmacological potential. Considering that the cambial variant present in Ipomoea is not causally related to the habit, the aim of this study is to list the group of anatomical features that define the “lianescent vascular syndrome” in the species, as well as to verify if there is variation between the stem and the root anatomy. Transverse and longitudinal sections of fresh material were analyzed qualitatively and quantitatively. Thus, it was found that the anatomy of the secondary xylem of I. cairica is similar to that of other species of Ipomoea, including indistinct growth rings, diffuse and porous vessels mainly solitary, simple perforation plate, alternate bordered pit, tyloses, heterocellular mainly uniseriate rays, and non-lignified parenchyma. The characteristics of the “lianescent vascular syndrome” is related to the high percentage of parenchyma. However, statistical analysis showed differences between stem and root in vessel diameter and vessel frequency, with higher values of vessel diameter and lower values of frequency of vessels in the root secondary xylem. These differences must be related to the environment in which the organ develops, as well as to the mechanisms involved in water conduction. Specific studies will make possible to test this hypothesis.

English

Sustainable management of economically and ecologically important tree species such as Faurea rochetiana merely depend on acquiring reliable information on growth dynamics and structure in response to the changing climate. Formation of the growth ring boundaries is pre-requisite for conducting several denroclimatology studies. Hence, the objective was to verify the formation of growth ring boundaries of F. rochetiana. Fifteen sample discs were examined for macroscopic and microscopic wood anatomy features and compared with IAWA list of microscopic features of hardwood identification for wood anatomy characterization. The result revealed that the studied tree had indistinct growth ring boundaries. Consequently, the studied tree is not a potential candidate for further denderoclimate studies.   Key words: Wood anatomy, growth ring, South Omo, Faurea rochetiana.

Qualitative Anatomical Characteristics of Compression, Lateral, and Opposite Woods in Pinus merkusii and Agathis loranthifolia

This study aimed to observe andcompare the qualitative anatomical characteristics of compression (CW), lateral (LW), and opposite (OW) woodsin the stem wood of Sumatran pine (Pinus merkusii) and Agathis (Agathis loranthifolia). The anatomical characteristics were observed using optical microscopy and scanning electron microscopy. CW showed a gradual transition from earlywood to latewood in both species, circular tracheid shape, many intercellular spaces, irregular tracheid tips, helical cavities, and slit-like bordered pits. CW of Sumatran pine showed an indistinct growth ring, whileCW of Agathis showed a distinct growth ring. Helical ribs occurred only in CW of Sumatran pine. LW and OW showed an oval tracheid with an angular outline, regular tracheid arrangement, and tapered tracheid tips in both species. LW and OW showed mainly uniseriate bordered pits in Sumatran pine, while LW and OW of Agathis frequently showed multiseriatebordered pits. CW, LW, and OW showed fusiform and uniseriate rays in Sumatran pine, while those of Agathis showed uniseriate rays. In conclusion, CW showed distinctive qualitative anatomical characteristics to LW and OW in both species, while LW and OW mainly showed similar characteristics. In particular, there were considerably distinctive characteristics between CW from both species.Keywords: Agathis, anatomical characteristics, reaction wood, Sumatran pine

Fossil wood from the Upper Cretaceous crater sediments of the Salpeterkop volcano, North West Province, South Africa

AbstractThe Salpeterkop volcano forms part of what has been referred to as the Upper Cretaceous Sutherland Suite of alkaline rocks, an igneous province composed of olivine melilitites, carbonatites, trachytes and ultramafic lamprophyres. Salpeterkop is a remnant of the summit tuff ring structure that surrounds a crater which is almost 1 km in diameter and is filled with epiclastic strata.Five pieces of silicified wood were collected from the crater filled sediments, sectioned and identified as a new species of Cupressinoxylon, C. widdringtonioides. This is the first example of the fossil genus in South Africa. Only one member of the Cupressaceae s.l. occurs in southern Africa today. From the wide and indistinct growth rings in the fossil wood it can be deduced that the local climate was warm and humid with little or no seasonality, in support of global records of a warm Late Cretaceous. The preservation of the crater further signifies the low level of erosion the region has experienced since its emplacement.

Charcoalified homoxylous woods from the Cenomanian of the Bohemian Cretaceous Basin (Czech Republic)

Three types of charcoalified fossil homoxylous woods are described from the Upper Cretaceous of the Bohemian Cretaceous Basin: Podocarpoxylon sp.,?Podocarpoxylon vel Taxodioxylon sp. and Protocupressinoxylon sp. They come from the uppermost part of the Peruc-Korycany Formation, which is mid-Cenomanian in age.Podocarpoxylon sp. shows distinct growth rings, uniseriate rays of medium height, 1–2 podocarpoid cross-field pits, and abietinean pitting on radial tracheid walls.Wood of ?Podocarpoxylon vel Taxodioxylon sp. differs in its indistinct growth rings, its rays which are uniseriate with medium height to multiseriate with horizontal resin duct, 1–2 podocarpoid cross-field pits per field, and mixed type of pitting on its radial tracheid walls.Protocupressinoxylon sp. also displays indistinct growth rings, and its rays are either uniseriate of medium height or multiseriate with horizontal resin ducts, but it has 1, occasionally 2–3 cupressoid cross-field pits per field, and abietinean to mixed pitting on radial tracheid walls.One of the three woods shows wood with growth rings, suggesting seasonally dry climate. The composition of the wood assemblage and its comparison with plant megafossils, sporomorphs and sedimentology suggest that there are two paleoenvironments in Unit 5 of the Peruc-Korycany Formation in the Pecínov quarry: a swampy coniferous forest in the coastal lowlands, and a mesophytic forest in the uplands.

Evaluation of physical, anatomical, and biometric characteristics of Citrus sinensis trees in longitudinal and transverse axes of stem

Three healthy Citrus sinensis (orange) trees in Babol, Iran, were randomly selected and cut. Two discs of 5 cm thickness were prepared along the tree (breast height and crown). In the transverse direction, the test specimens were cut 2 × 2 cm to 3 cm from the pith to the bark sequentially and examined. The biometric and physical properties were measured, and microscopic sections of wood near the bark were studied using light microscopy according to the International Association of Wood Anatomists’ (IAWA) List. Anatomical examination of the C. sinensis wood showed that the species was a diffuse porous hardwood, with indistinct growth rings, simple perforation plates, alternate intervessel pits, and banded parenchyma. The basic density and oven-dry density increased from the pith towards the tree bark and from the bottom of the tree towards the crown. There was a significant difference in both the transverse and longitudinal directions of the C. sinensis tree in terms of fiber length, fiber lumen diameter, fiber diameter, and cell wall thickness. The mean fiber length, fiber diameter, fiber lumen diameter, and cell wall thickness were 0.76 mm, 23.64 µm, 9.23 µm, and 14.41 µm, respectively.

The fossil genus Aextoxicoxylon (Magnoliopsida) in the Upper Cretaceous Puntudo Chico Formation, Chubut Province, Argentina

A new fossil dicot wood recovered from the Upper Cretaceous Puntudo Chico Formation is here identified as a representative of the fossil genus Aextoxicoxylon. Differences with the type species support the recognition of a new species, Aextoxicoxylon kawasianus sp. nov. This new taxon is characterized by having indistinct growth rings, solitary vessels, diffuse porosity, perforation plates scalariform with high number of bars, and heterocellular rays. All these features are typical of primitive woods according to Baileyan trends. Furthermore, anatomy of the wood, and the presence of fungal hyphae in vessels, suggests non-seasonal and probably warm and humid climate, which agrees with previous proposals for the Puntudo Chico Formation and other units of similar ages. Aextoxicoxylon is a new element previously not recognized in the Late Cretaceous to Danian floristic assemblages that seem to have been linked to the Kawas Sea, a shallow sea that developed in Patagonia at the end of the Cretaceous.

Anatomical Structures and Fiber Quality of Four Lesser-Used Wood Species Grown in Indonesia

This study aimed to investigate the anatomical structure and fiber quality of four lesser-used wood species namely Benuang (O. sumatrana), Duabanga (D. moluccana), Pisang Merah (H. hellwigii), and Terap (A. odoratissimus). This study evaluated its suitability for raw material in pulp and paper manufacturing. The anatomical structure was observed macro- and microscopically. Macroscopic structures were observed directly to the wood samples, while microscopic characteristics were observed through microtome specimens. Fiber dimension was measured through macerated specimens and fiber quality was analyzed following the Rachman and Siagian’s method. Results showed that these four timber species have similarity in the indistinct growth ring, diffuse porous in a radial pattern, rounded solitary vessel outline, 1 to 3 cells of ray width, deposits within the rays, fiber length, and cell wall thickness. Differences were found on vessel diameter, vessel grouping, vessel frequency, tyloses existence, type of axial parenchyma, and ray height. Based on fiber length and its derived values, the wood fibers of all species studied are suitable for pulp and paper manufacturing. They belong to the II quality class. The produced pulp and paper would have good quality, especially in tensile, folding, and tear strength. To promote their utilization, silviculture aspect of these four species has to be well understood.

Improved tree-ring visualization using autofluorescence

The great diversity of wood anatomical features found in trees worldwide results in a broad variety of growth-ring boundary types that are not always easy to recognize, especially in tropical woods. However, the presence of clearly visible limits between tree rings is essential for any tree-ring studies. Here, we propose the use of autofluorescence of wood in order to enhance tree-ring visualization. The multispectral light emitted from the fluorescence stereomicroscope can be filtered in specific wavelengths to improve the visualization of wood anatomical features. To evaluate the effectiveness of this technique, we compared visualization under natural light, GFP (green fluorescent protein) filter, RFP (red fluorescent protein) filter and UV filter. We tested this technique with a set of 38 tree species with different types of growth-ring boundaries. Although results are species-specific, fluorescence has been shown to improve the visualization of growth-ring boundaries by enhancing the contrast among cell types. It may highlight fibrous zones (e.g. Cavanillesia arborea, Aspidosperma polyneuron), different porosity patterns (e.g. Myracrodruon urundeuva), secretory canals (e.g. Copaifera langsdorffii), and parenchyma bands (e.g. Tipuana tipu). Fluorescence allows the visualization of growth-ring boundaries in species that were previously described as having indistinct growth rings under natural light. For species with clear tree-ring boundaries such as Cedrela fissilis and Hymenaea courbaril, this approach aids the identification of false rings. In addition to the visualization of growth-ring boundaries, autofluorescence may be useful for other qualitative and quantitative analyses of wood anatomy, such as wood identification and automated measurements of anatomical features. Scientists struggling with tree-ring counting and cross-dating due to difficult tree-ring visualization may find fluorescence useful. It may also aid to identify new species suitable for tree-ring studies.

A new species of Carlquistoxylon from the Early Cretaceous of Patagonia (Chubut province, Argentina): the oldest record of angiosperm wood from South America

ABSTRACT An angiospermous wood from the Lower Cretaceous (upper Albian) of the Cerro Barcino Formation, Chubut Group, central Patagonia, Argentina, is described. Its estimated minimum diameter is 40 cm and it is significant as the oldest known angiosperm wood for South America. It has indistinct growth ring boundaries, vessels solitary and in radial multiples, simple perforation plates, alternate intervessel pits, vessel-ray parenchyma pits oval to horizontally elongated, heterocellular rays, non-septate fibres, axial parenchyma absent, and abundant tyloses. Because this Albian wood has non-septate fibres we assign it to Carlquistoxylon, even though it has a general combination of characters similar to that of Paraphyllanthoxylon, which has septate fibres. The number of vessels per radial multiple, vessel tangential diameter and frequency, vessel-ray parenchyma pitting, and absence of axial parenchyma distinguish the fossil described here from the only previously known species of Carlquistoxylon: Carlquistoxylon nacimientense; therefore, a new species is erected. Because of the close similarities between this new specimen and Paraphyllanthoxylon species, comparisons with all the species included in both genera are provided. Systematic affinities for this wood are discussed considering previous discussions for both Paraphyllanthoxylon and Carlquistoxylon affinities. As the oldest described angiosperm wood in South America to date, this specimen provides critical information on the diversity and growth habit of Cretaceous angiosperms from the Southern Hemisphere.

Stem anatomy at various developmental stages of secondary growth in Turbina corymbosa (Convolvulaceae)

Background – Population growth of lianas in the tropical forest is credited to their ability of CO2 sequestration and efficiency of the narrow stems to supply water required for the amount of foliage it bears. Turbina corymbosa (L.) Raf. (Convolvulaceae Juss.) is one of the fast-growing invasive species of scrambling woody lianas. It covers trees entirely within a short period to compete with above-ground resources (particularly sunlight). However, no information is available on how it manages to cope up with an increasing demand of water supply and mineral nutrients. What are the structural and developmental patterns adapted by this species to expand the stem diameter for efficient supply of below-ground resources? Therefore, our aim was to investigate the secondary growth patterns and structure of secondary xylem and phloem in T. corymbosa.Methods – Several samples of the stem with various diameters were studied using a histological method. Morphological and anatomical analyses were carried out using light microscopy.Key results – With the initiation of secondary growth, stems lose their circular outline rapidly due to unequal deposition of secondary xylem and formation of successive cambia. New successive cambia initiate from parenchymatous cells as small crescent-shaped fragments on asymmetric/opposite sides and result in a different stem conformation. Though several segments of successive cambia are formed, very few stem samples form complete cambium rings. The secondary xylem formed by successive cambia is diffuse porous with indistinct growth rings and is composed of both wide and narrow (fibriform) vessels, tracheids, fibres, axial and ray parenchyma cells. The secondary phloem consists of sieve tube elements, companion cells, axial and ray parenchyma cells. In fully grown plants, cambial action (internal cambium) occurrs between the intraxylary phloem and protoxylem and produces secondary xylem and phloem near the pith region.Conclusion – Structural alterations and unequal deposition of conducting elements, occurrence of intraxylary phloem and flattening of the stem are suggested to facilitate rapid growth of the plants by providing required minerals and nutrients. Internal cambium formed at the periphery of the pith is bidirectional and produces secondary xylem externally and intraxylary phloem internally. Continued development of intraxylary phloem from the internal cambium provides an additional path for rapid and safe translocation of photosynthates.