Vasicentric Tracheids Research Articles

Wood of Qualea from the Piedra Chamana in-situ fossil forest (late Middle Eocene, Peru) and the comparative wood anatomy of Vochysiaceae and Myrtaceae

Summary A wood from a late Middle Eocene in-situ fossil forest in northern Peru shows affinity with Qualea (Vochysiaceae), a genus of South American lowland tropical trees, based on features including vestured pits, aliform-confluent to banded paratracheal parenchyma, and homocellular rays. Additional features suggest adaptation to dry conditions. The fossil is named as a new species within Qualeoxylon (Q. lafila). Vochysiaceae and sister-group Myrtaceae share features unique to Myrtales (vestured pits, intraxylary phloem) or common in the order (vessels generally solitary and in >1 diameter class, heterocellular rays) but in other ways are clearly differentiated. Vochysiaceae has narrow to very wide vessels with elaborated axial parenchyma and lacks most characters considered less specialized such as scalariform perforations. Myrtaceae generally has vessels with vasicentric tracheids, usually exclusively solitary, very narrow to wide, and often diagonally arranged, and includes taxa with less to more specialized features. Woods with elaborated paratracheal parenchyma and vessels wide to very wide occur in wet tropical forest environments in both families Erisma, Vochysia and Qualea/Ruizterania (Vochysiaceae) in the Neotropics and Syzygium (Myrtaceae) in the Asian tropics. The Eucalyptus spp. dominating open forests in Australia have typical myrtaceous features (including vasicentric tracheids) plus homocellular rays, whereas the eucalypt clade Angophora + Corymbia, occurring mainly in the northern, monsoonal regions of Australia, has both vasicentric tracheids and aliform to banded axial parenchyma. The fossil is an early record for Vochysiaceae and adds to indications that Vochysiaceae and sister-group Myrtaceae showed significant diversification by the late Paleogene.

The role of imperforate tracheary elements and narrow vessels in wood capacitance of angiosperm trees

Summary There is a broad diversity of imperforate tracheary elements (ITEs) — libriform fibers, fiber-tracheids, true tracheids and vasicentric/vascular tracheids — described thoroughly by Sherwin Carlquist. However, in a quantitative sense, the functional meaning of different ITE types present in the wood of vessel-bearing angiosperms remains unclear because very few structure–function studies measure ITEs’ properties. ITEs with abundant pits and wide pit borders — vascular tracheids, vasicentric tracheids, and true tracheids sensu Carlquist — have been shown to conduct water and, thanks to this conductive ability and the multitude of pits, they could also contribute to wood capacitance. A dataset of 30 temperate angiosperm tree species was reanalysed to record the presence/absence of true, vasicentric, and vascular tracheids including data on conduits15 fraction and vessel-conduit15 contact fraction (conduits15 were defined as cells resembling vessels and with a maximum lumen diameter of 15 μm. They encompassed narrow vessels, vasicentric tracheids, and vessel tails). The presence of tracheids, conduits15 fraction, and contact fraction had no effect on wood capacitance, except, per given wood volumetric lumen water content, species with true tracheids tended to have lower capacitance. These results suggest that the presence of tracheids or conduits15 properties do not limit wood capacitance, but the results do not exclude the potential role these cells may play in internal water dynamics.

Seasonal temperature and precipitation regimes drive variation in the wood of oak species (Quercus) along a climatic gradient in western Mexico

Summary To achieve optimal balance among wood’s support, storage, and transport functions, tree species present adaptive variation in wood anatomical traits. Oaks (Quercus) are woody plants that are dominant in many ecosystems, possess wide variation in wood traits, and can tolerate water stress in diverse habitats. Mountain regions contain steep climatic gradients that exert strong environmental pressures on wood traits. The aims of this study were: (1) to quantify the anatomical variation in 21 oak species distributed along an environmental gradient and (2) to analyze the interspecific variation among the studied species. Fibres and parenchyma fractions were the most abundant cell types. We found a trade-off between total fibre fraction and total parenchyma fraction modulated by the precipitation during the warmest quarter in which oak species in drier areas invested more in support cells. The 21 oak species studied showed vasicentric tracheids, which could be essential to compensate for the transport system in drier areas. Wood density was negatively correlated with the axial parenchyma fraction and fibre lumen width. Oak species have high interspecific variation in the total vessel fraction and vessel diameter. Anatomical variation in oak species along a climatic gradient showed a broad continuum of fibre characteristics from wide to narrow wall and lumen, abundant to scarce parenchyma, and wide to narrow vessels. These variations imply a diversification of ecological strategies within the genus that includes the vascular design of the stem to define the tolerance and competitiveness of the oak species.

Effect of drought stress on the formation and lignification of eucalyptus wood cells

Summary Environmental adaptation and cell differentiation processes are factors that influence the anatomical elements of wood. The objective of this study was to investigate the effect of water deficit on lignin composition in anatomical elements and on the characteristics of vessel-neighboring cells. Six-year-old clones of Eucalyptus urophylla and Eucalyptus grandis × Eucalyptus camaldulensis from wet and dry regions were used. All regions received a rainfall exclusion treatment. Cell wall width, cell wall thickness, and form factor of fibers close to and far from vessels were measured. In the same cells, lignin was measured in the middle lamella and vessels by a fluorescence technique. The vessel differentiation process affected cell wall thickness and lignin composition in neighboring cells. Lignin composition was increased in vessels compared to fibers or vasicentric tracheids. Middle lamella lignin was not affected by vessel differentiation or water deficit in either eucalyptus clone. E. grandis × E. camaldulensis is originally from a dry climate region and, therefore, did not suffer alterations in lignin when subjected to water stress conditions; however, this clone exhibited a higher number of vasicentric tracheids. E. urophylla is originally from a humid climate region and, when subjected to water deficit, showed increased wood lignin composition, which seems to be a strategy for better use of water resources. Alterations in lignin composition of vessel, vasicentric tracheid, and fiber cell walls resulting from exposure to water deficit conditions vary according to eucalyptus species.

Adaptive variation among oaks in wood anatomical properties is shaped by climate of origin and shows limited plasticity across environments

Abstract Climate is a major evolutionary force in driving adaptive differentiation and plasticity in plant function. Xylem anatomy and hydraulic architecture are critical to water use, growth and responses of trees to drought and thus important in delimiting their ecological niches. How wood properties have been shaped through evolution by their climatic origins and the importance of plasticity for species persistence remain open questions critical to understanding plant responses to changing climate. We measured 11 wood anatomical traits for 18 Quercus (oak) species in arboreta that span contrasting climates (California‐US, southwestern France and central England). We investigated coordinate evolution of xylem anatomical properties with climatic niche and intraspecific variation in relation to growth environment. Species originating from climates with drier summers had traits associated with higher resistance to drought—higher density of vasicentric tracheids (VT), lower vessel hydraulic diameter (Dmh) and lower hydraulic conductivity. Species that evolved in climates with drier, hotter summers or colder winters had higher numbers of VT than those from mesic climates, supporting hypotheses that VT are critical for water transport during drought. We found limited intraspecific variation in xylem traits associated with growth environment—only four traits (pit fraction, VT, vessel density and Dmh)—differed among gardens. Xylem traits showed high lability across the phylogeny, consistent with evidence for parallel sympatric adaptive radiation and global diversification of the oaks. Our results provide evidence for the physiological mechanisms that underlie adaptation to changing environments and responses to climate change.

New dicotyledonous woods from the San Carlos Formation (Upper Cretaceous) in Northern Mexico

Summary We describe two new fossil woods from the San Carlos Formation (Upper Cretaceous), Chihuahua State, Mexico. The first wood resembles the fossil genus Metcalfeoxylon in having solitary vessels, scalariform perforation plates, vessel-ray parenchyma pits of similar size as the intervessel pits, axial parenchyma apotracheal diffuse and diffuse in aggregates, and heterocellular multiseriate rays with long, uniseriate tails. The second wood is a new fossil genus, and it is characterized by having diffuse porous wood, vessels predominantly solitary, vessel outlines oval and tending to be of two diameter classes, simple perforation plates, minute alternate intervessel pits, vessel-ray parenchyma pits similar to intervessel pits in size and shape, vasicentric tracheids, non-septate fibers, homocellular rays, and exclusively uniseriate and biseriate rays. This combination of features supports its placement in Myrtales (?Myrtaceae), in a new fossil-genus named Lazarocardenasoxylon. These two new records provide more information about the floristic composition of the Late Cretaceous flora of the San Carlos Formation and its relationship with those from the southern USA. However, a definitive picture of the floristic relationship of these Cretaceous floras of northern Mexico and southern USA remains elusive.

Hydraulic function and conduit structure in the xylem of five oak species

Abstract Many plant lineages, including oaks (Quercus spp.), have both vessels and tracheids as hydraulically conductive cells within their xylem. The structure of these co-occurring conduit types and their contribution to plant hydraulic function have been relatively little studied. We hypothesized that vasicentric tracheids contribute to hydraulic function under conditions of low water availability. We predicted that within a species, oaks growing at drier and warmer low elevation sites would have more tracheids and be more embolism resistant compared to those growing at moister and colder higher elevation sites. We also predicted that across species, lower elevation oaks would have increased tracheid abundance within their xylem. Five oak species differed in many xylem traits, including vessel diameter and length, tracheid size and abundance, embolism resistance, and hydraulic conductivity. Tracheids were most abundant in the xylem of the highest elevation species at sites that receive winter snow and freezing temperatures. Vessels were relatively vulnerable to embolism as confirmed with multiple methods, including centrifuge vulnerability curves, micro-CT scans of native stem samples, and single vessel air injection. Theoretical conductivity calculations indicated that tracheids account for 5.7–15.5% of conductivity in hydrated stems, with tracheids likely increasing in importance as large diameter vulnerable vessels embolize. The occurrence of both vessels and vasicentric tracheids in the xylem of oaks may enable them to function within highly seasonal climates. Tracheids, though often overlooked, may be particularly important in maintaining conductivity throughout much of the year when water potentials decline from seasonal maximums and following freeze-thaw events.

Characterization and comparison of the wood anatomical traits of plantation grown Quercus acutissima and Quercus variabilis

Abstract Oaks are important tree species, providing essential biomaterial for the wood industry. We characterize and compare wood anatomical traits of plantation grown Quercus acutissima Carruth. and Q. variabilis Blume to provide more detailed information to understand xylem radial growth, structure, and function, as well as differences between sapwood and heartwood, to provide data relevant for tree breeding and value-added wood utilization of oak plantations in China. In this study, radial strips were collected at breast height from the main trunk of the two species. Latewood percentage and growth ring width were investigated by X-ray densitometry and a Tree Ring Analysis System, respectively. Vessel and fibre lumen diameter, vessel and fibre wall thickness, vessel density, fibre wall thickness/diameter ratio, tissue proportions, and pit membrane thickness in between vasicentric tracheids were observed with light microscopy and electron microscopy and quantified. There were significant differences in a few wood anatomical traits between the two species: vessel wall thickness and vessel lumen diameter were higher in Q. acutissima than in Q. variabilis, while higher axial parenchyma proportion in sapwood was found in Q. variabilis than in Q. acutissima. More abundant tyloses were found in heartwood than in sapwood of both species. Our work showed the intraspecific and interspecific variation of the two species. Most differences between sapwood and heartwood must be attributed to differences in cambial age during their formation.

Charcoalified wood from the cenomanian of gard (Southern France): An insight into early angiosperm palaeoecology

The discovery in the Cenomanian (early Late Cretaceous) of Southern France of several localities with abundant charcoal has brought to light several angiosperm wood types. This is the oldest angiosperm wood assemblage discovered yet for Europe. Here we analyse this assemblage, with emphasis on features recognized to be of particular palaeoecological and climatic significance for the Cainozoic according to earlier studies and comparing the inferred results to those from other independent lines of evidence (sedimentology, palynology, isotopic geochemistry, etc.). Vessel diameter and distribution, perforation plates, abundance of vascular tracheids and of septate fibres, presence of diffuse axial parenchyma perhaps should not be used as palaeoecological proxies for the Cretaceous because they do not seem to clearly correlate with other lines of evidence that indicate warm tropical conditions. The abundance of fibre-tracheids fits with the other sources of data, but our results are probably biased by preservation problems. On the contrary, the occurrence of growth-rings, porosity, vessel density, occurrence of vessel groups, occurrence of vasicentric tracheids and of some paratracheal to vasicentric and banded axial parenchyma correlate well with other palaeoclimate indicators. These results show that these features can be used for palaeoclimatological inferences during the early Late Cretaceous

Xylem vessel‐diameter–shoot‐length scaling: ecological significance of porosity types and other traits

AbstractFlowering plants predominantly conduct water in tubes known as vessels, with vessel diameter playing a crucial role in plant adaptation to climate and reactions to climate change. The importance of vessels makes it essential to understand how and why vessel diameter, plant height, and other ecological factors are interrelated. Although shoot length is by far the main driver of variation in mean vessel diameter across angiosperms, much remains to be understood regarding the factors accounting for the abundant variation around they‐axis in plots of mean species vessel diameter against shoot length. Here, we explore the potential role of porosity types, wood density, leaf phenology, background imperforate tracheary element type, vasicentric tracheids, vascular tracheids, perforation plate type, and successive cambia in causing variation in they‐intercept or slope of the mean species vessel‐diameter– and vessel‐density–shoot‐length associations at the shoot tip and base. We detected numerous cases of ecologically significant variation. For example, latewood vessels of ring porous species scale with a lower slope than earlywood, i.e., latewood vessels are relatively narrow in taller plants. This pattern is likely the result of selection favoring freezing‐induced embolism resistance via narrow vessels. Wood density was negatively associated with vessel diameter, with low wood density plants having wider vessels for a given height. Species with scalariform perforation plates scale with a lower shoot base vessel‐diameter–shoot‐length slope, likely reflecting selection against scalariform plates in wide vessels. In other cases, functional groups scaled similarly. For example, species with successive cambia did not differ from those with conventional single cambia in their mean vessel‐diameter–shoot‐length scaling, rejecting our prediction that species with successive cambia should have narrower vessels for a given shoot length. They did, however, have fewer vessels per unit shoot cross‐sectional area than plants of similar heights, likely because vessels have longer functional lifespans (and therefore are fewer) in species with successive cambia. Our methods illustrate how vessel diameter can be studied taking shoot length into account to detect ecologically important variation and construct theory regarding plant adaptation via the hydraulic system that includes plant size as a vital element.

COMPARATIVE WOOD ANATOMICAL PROPERTIES OF GENUS SYZYGIUM (FAMILY MYRTACEAE) FROM MANIPUR, INDIA

Syzygium belongs to family Myrtaceae and comprises of mostly trees and a few shrubs. The main objectives were to study anatomical and physical characteristics of five Syzygium species namely Syzygium cumini, Syzygium fruticosum, Syzygium jambos, Syzygium nervosum and Syzygium praecox and to see intra and inter species variation among them. The wood samples were taken at breast-height from straight bole and uniform crowned trees. The present study showed that all the selected species shared common features like simple perforation plate, vestured inter-vessel pits, vessel-ray pits, disjunctive ray parenchyma cells, diffuse, diffuse-in-aggregate, vasicentric, aliform and confluent types of axial parenchyma Diffuse porous and indistinct fruticosum were observed. The vessels were mostly barrel shaped with small or long tails at one or both ends in all species except tube shaped in S. jambos and drum shaped in S. fruticosum. Spiral thickenings were present in the tails of S. nervosum and S. fruticosum. Fibres were thin walled and non-septate. Occasional septate fibres and vasicentric tracheids were present in S. nervosum and S. jambos. Crystals in ray of S. nervosum and S. fruticosum and silica bodies in axial parenchyma of S. jambos were observed. The fibre percentage and wood density were maximum in S. jambos whereas moisture content was minimum in S. jambos. Principal Component Analysis revealed a close relationship among all species. Therefore, the qualitative characteristics and all quantitative anatomical characteristics can be used for reliable identification of Syzygium species.

New insights into wood anatomy and function relationships: How Eucalyptus challenges what we already know

Multispecies surveys have shown that there is a weak but significant trade-off between xylem efficiency and safety in woody species, with no species maximizing both attributes at the same time. Relationships between xylem structure and function are studied mostly at the interspecific level, with few studies considering the relationships at the intraspecific level, particularly in angiosperms. Studies have shown that relationships between xylem anatomy or wood density and vulnerability to cavitation (which determines xylem safety) observed in multi-species surveys may be different to those observed within a species. This raises the question about the value of multispecies studies to shed light over what is adaptive within a given species, the organization level at which natural and human selection operates. To contribute to this debate, we studied xylem structure and function in four Eucalyptus species, and made focus within one of them, E. globulus, to determine if patterns observed at the interspecific level are also held within a species. Eucalyptus species have a xylem composed by solitary vessels surrounded and connected to imperforate tracheary cells and parenchyma, a particular anatomy poorly known in terms of its function. Correlation analyses revealed that the trends observed between vessel size (mean and distribution) and vulnerability to cavitation are similar at the interspecific and intraspecific levels. Moreover, no trade-off has been observed between xylem efficiency (maximum hydraulic conductivity) and safety (water potential at 12% and 50% of hydraulic conductivity loss), but the opposite trend: individuals with mean larger vessels presented lower vulnerability to cavitation. Cells around vessels (parenchyma, vasicentric tracheids, fibertracheids) could be involved in this phenomenon since they correlate both with maximum hydraulic conductivity (positively) and vulnerability to cavitation (negatively) at the interspecific level. In addition, large xylem vessels presented smaller pits than small xylem vessels. This suggests that pit size is involved in the lack of trade-off between xylem safety and efficiency. Finally, vulnerability to cavitation was correlated with branch and stem wood density of the same tree, but correlations had opposite sign depending on the plant organ. These results provide new insights into the relationships between wood structure and function of angiosperm species.

Identifying which conduits are moving water in woody plants: a new HRCT-based method.

In vivo imaging methods are useful for examination of plant vascular tissues, particularly in the identification of fluid vs gas-filled conduits; however, these methods may not allow for the simple identification of conductive conduits. Our aim in the present study was to develop a method that would allow for the in vivo identification of conductive conduits. Intact plants and segments of grapevine (Vitis vinifera L.) and intact American chestnut (Castanea dentata (Marshall) Borkh.) saplings were examined. We found that iohexol, a water soluble iodine-rich molecule, was a useful contrast agent. We also stained the xylem of segments and gas- dried samples to compare between intact scans and excised segments. Iohexol could be readily fed through cut roots or stems into the transpiration stream, was successfully transported through the xylem and marked conductive vessels within high-resolution computed tomography (HRCT) scans. Iohexol results were comparable to those obtained by staining cut segments, with iohexol detecting greater numbers of smaller conduits in some samples. Samples contained gas-filled conduits, as well as both conductive (containing iohexol tracer) and non-conductive (no iohexol tracer) fluid-filled vessels. Fluid-filled non-conductive vessels were likely still developing or were not connected to the sap stream by a low resistance pathway. We found minimal differences between intact and excised segments other than excision-related dilution of iohexol. Both vessels and vasicentric tracheids were filled with iohexol in chestnut, providing a new tool to study the functions of these different cell types. The use of iohexol as a tracer to identify conductive vessels may greatly improve the utility of HRCT as a tool in the study of plant hydraulic function. Future studies using HRCT will likely need to incorporate conductive vessel markers or controls into experiments due to the presence of non-conductive fluid-filled vessels within the xylem.

Biogeographic Implications ofMammea paramericanasp. nov. from the Lower Miocene of Panama and the Evolution of Calophyllaceae

Premise of research. Mammea (Calophyllaceae) is a pantropical genus of 70 tree species, most of which are native to Madagascar. We describe a new species of Mammea on the basis of a fossil stem from the lower Miocene of Panama, discuss its implications for the biogeography of the genus, and assemble a set of morphological characters to examine the phylogeny of Calophyllaceae and confirm our identification.Methodology. We prepared the fossil stem using the cellulose acetate peel technique and compared its anatomy with that of extant plants, including a specimen of Mammea americana obtained from Puerto Rico, and with that of other fossils. For our phylogenetic analysis, we modified a previously published morphological matrix of reproductive and vegetative characters and added 14 wood characters, for a total of 66 characters.Pivotal results. Distinctive anatomical features of Mammea paramericana sp. nov. include predominantly solitary vessels, vasicentric tracheids, fibers with distinctly bordered pits in bo...

First insights into the functional role of vasicentric tracheids and parenchyma in eucalyptus species with solitary vessels: do they contribute to xylem efficiency or safety?

The relationship between hydraulic specific conductivity (ks) and vulnerability to cavitation (VC) with size and number of vessels has been studied in many angiosperms. However, few of the studies link other cell types (vasicentric tracheids (VT), fibre-tracheids, parenchyma) with these hydraulic functions. Eucalyptus is one of the most important genera in forestry worldwide. It exhibits a complex wood anatomy, with solitary vessels surrounded by VT and parenchyma, which could serve as a good model to investigate the functional role of the different cell types in xylem functioning. Wood anatomy (several traits of vessels, VT, fibres and parenchyma) in conjunction with maximum ks and VC was studied in adult trees of commercial species with medium-to-high wood density(Eucalyptus globulus Labill., Eucalyptus viminalis Labill. and Eucalyptus camaldulensis Dehnh.). Traits of cells accompanying vessels presented correlations with functional variables suggesting that they contribute to both increasing connectivity between adjacent vessels-and, therefore, to xylem conduction efficiency-and decreasing the probability of embolism propagation into the tissue, i.e., xylem safety. All three species presented moderate-to-high resistance to cavitation (mean P50 values=-2.4 to -4.2 MPa) with no general trade-off between efficiency and safety at the interspecific level. The results in these species do not support some well-established hypotheses of the functional meaning of wood anatomy.

Age trends in the wood anatomy of Quercus faginea

The wood anatomy of Quercus faginea, an oak native to the Iberian Peninsula and the Maghreb in Africa, is described and age trends of fibres and ray dimensions are recorded. The analysis was made on a total of 20 trees from two different sites in Portugal. The wood structure within both sites was similar. Quercus faginea shares its microscopic characteristics with other species of the white oak group; i.e., it was not easily distinguishable from other European oaks. The wood is ring porous with wide multiseriate rays and a high proportion of fibres and vasicentric tracheids. There was an increase of fibre and ray dimensions from the pith outwards. Fibre length started to stabilize around 30 years of age up to 50–60 years and decreased afterwards under a traditional rotation period (100–150 years). Linear and polynomial adjustments fitted better the fibre variation at younger and older ages, respectively. Rays were quite homogeneous within the trees. Cambial age accounted less to total variation than individual trees at both sites; i.e., tree-to-tree variation is greater than variation related to maturation or cambial age. The average dimensions of fibres and rays were similar between sites.

Myrtineoxylon gen. nov.: The first fossil wood record of the tribe Myrteae (Myrtaceae) in eastern Asia

AbstractThe new genus and species Myrtineoxylon maomingensis is described from the Late Eocene Youganwo Formation of Maoming Basin, South China. It is the first record of fossil wood from eastern Asia assigned to Myrtaceae. The combination of solitary vessels, simple perforation plates, alternate vestured intervessel pits, bordered vessel–ray pits, vasicentric tracheids, ground tissue fibre–tracheids, diffuse and diffuse–in–aggregate parenchyma in 3–8 cells strands, and 1–3–seriate, strongly heterocellular rays, and absence of crystals is suggestive of a position of the fossil in the tribe Myrteae (informal "Australasian group"), a basal lineage in Myrtaceae. This is the first fossil record from eastern Asia and from all of Eurasia confidently referred to this tribe.

A Ranunculalean Liana Stem from the Cretaceous of British Columbia, Canada:Atli moriniigen. et sp. nov.

Premise of research. The lianoid habit is found in 125 extant plant families and is most diverse and abundant in structurally complex forests, such as tropical forests. A stem with lianoid anatomy is described from Cretaceous sediments of Hornby Island, British Columbia.Methodology. The stem segment, 2.5 cm in diameter and 2.8 cm long, was studied using the cellulose acetate peel technique and SEM. Anatomy was documented and compared to fossil and modern taxa.Pivotal results. The stem lacks distinct growth increments, and the fibrous wood is dissected by large (>10 cells wide) rays. Wood is diffuse porous with mostly solitary vessels, rarely in tangential multiples (2–4). Vessel elements have a mean tangential diameter of 198 μm and mean length of 527 μm, bearing medium to large, crowded, elliptical to flat-elliptical alternate pits. Axial parenchyma is diffuse and vessels are surrounded by vasicentric tracheids with alternate bordered pitting. Rays are homocellular and >2 cm tall. Phloem rays are dilated, protruding into the xylem rays; thick-walled ray cells contain prismatic crystals. Periderm is composed of thin-walled cells interspersed with sclerotic nests. Wood anatomy of the fossil shows the most similarity to that of lianas in the Menispermaceae, Lardizabalaceae, and Ranunculaceae.Conclusions. The Hornby Island stem represents a new taxon, Atli morinii gen. et sp. nov. (Ranunculales). This liana specimen expands our knowledge of Cretaceous biodiversity and points to the presence of structurally complex forests on Hornby Island in the Campanian. Anatomy of Atli and other Cretaceous liana stems combines characteristics of several families in Ranunculales, documenting past anatomical diversity and possible stem lineage mosaicism. The most diverse lianoid lineages currently known from the Cretaceous and Paleogene are early-divergent eudicots, particularly Ranunculales and Vitales that account for more than 50% of described lianoid species during this key time period of angiosperm diversification.

WOOD ANATOMY OF MYRCIARIA, NEOMITRANTHES, PLINIA AND SIPHONEUGENA SPECIES (MYRTEAE, MYRTACEAE)

Myrciaria, Neomitranthes, Plinia and Siphoneugena are closely related genera whose circumscriptions are controversial. The distinctions between Myrciaria vs. Plinia, and Neomitranthes vs. Siphoneugena, have been based on a few fruit characters. The wood anatomy of 24 species of these genera was examined to determine if wood anatomical features could help delimit the genera. It was determined the four genera cannot reliably be separated by wood anatomy alone. Characteristics seen in all four genera are: growth rings usually poorly-defined; diffuse porous; exclusively solitary vessels, usually circular to oval in outline; simple perforation plates; vessel-ray pits alternate and distinctly bordered; fibers with distinctly bordered pits in radial and tangential walls, usually very thickwalled; vasicentric tracheids typically absent; scanty paratracheal parenchyma, sometimes unilateral, and diffuse to diffuse-in-aggregates; chambered crystalliferous axial parenchyma in many species, usually both prismatic and smaller crystals; rays 1–4-seriate, uniseriate rays composed of upright/square cells, multiseriate rays with procumbent body cells and 1 to many marginal rows of upright/square cells; disjunctive ray parenchyma cells usually present.

Wood anatomical variations in some species of Quercus of Meghalaya

The main aim of present study is to gather original information on anatomical features and variations in dimensions of wood elements of some Quercus species of Meghalaya. All species of Quercus show diffuse porous wood with indistinct growth rings except Q. acutissima which shows tendency towards semi ring porous and Q. semiserrata with fairly distinct growth rings. Vessels are solitary or radial multiple of two arranged in radial or diagonal pattern. All species of Quercus show presence of scalariform perforation plates and vasicentric tracheids. Aggregate rays are present only in Q. acutissima where as Q. lanceofolia and Q. semiserrata show the presence of multiseriate rays. Both homocellular and heterocellular rays are present in Quercus species except Q. acutissima and Q. fenestrata which show only heterocellular rays. Axial parenchyma is apotracheal diffuse in all species except Q. acutissima that shows diffuse in aggregate, banded and unilateral paratracheal parenchyma in addition to apotracheal diffuse. Chambered crystals are present in Q. dealbata and Q. fenestrata.Tissue proportion of different wood elements shows that fiber percentage is maximum in all species. Variance ratio (F test) indicates that there are statistically significant differences in wood elements dimension namely fiber length, fiber diameter, vessel diameter, vessel density and wood density. Also a positive and significant correlation exists between fiber diameter and wall thickness while other parameters are not correlated with each other.