Helical Thickenings Research Articles

Identification of neogene woods from Alaska-Yukon

Woods collected from early Middle Miocene to Late Pliocene localities at high latitudes (more than 60° N) of Alaska and Canada were examined microscopically to determine taxonomic affinities. All were conifers and most are Pinaceae. Features useful in the identification of conifers are reviewed, including characteristics of growth rings, resin canals, cross-field pitting, ray tracheids, longitudinal and ray parenchyma, helical thickenings and cell sizes. Some of the problems in feature recognition in fossil conifer woods due to compression and fungal and microbial degradation are discussed. Although relatively few wood samples were examined, these samples provide information consistent with that derived from the pollen, leaf, and fruit and seed record obtained from the same deposits, and provide additional documentation for a cooling of climate and changes in the flora and vegetation from the early Middle Miocene to the Late Pliocene. In the early Middle Miocene samples from northeastern Alaska, there are woods of Taxodiaceae and soft pines ( Pinus spp.) with growth rings greater than 1 cm wide; in the Late Pliocene there are woods of spruce ( Picea) and larch ( Larix) with growth rings less than 1 mm wide.

Arrangement of cortical microtubules during formation of bordered pit in the tracheids ofTaxus

The arrangement of cortical microtubules during the development of the secondary wall and bordered pits in the tracheids ofTaxus was examined by immunofluorescence and electron microscopy. The cambial region of radial longitudinal sections of developing young shoots (2–3 years old) contains cells at various stages of differentiation from cambial cells to tracheids. At the early stage of formation of bordered pits, circular bands of microtubules were seen to be associated with the inner edge of the border of the developing pit. In other regions than the pit secondary wall of uniform thickness was laid down, and obliquely oriented cortical microtubules ran parallel to one another. These cortical microtubules also covered the surface of the border of the developing pit on the side facing the center of the cell. As the border of the pit developed, a circular band of MTs remained associated with the inner edge of border, suggesting that the MTs were involved in the formation of the rim of the bordered pit, extending the initial border thickening, which consisted of concentrically oriented cellulose microfibrils. After completion of the formation of the bordered pit, helical thickenings became apparent. The obliquely oriented microtubules were organized in bands parallel to one another, being superimposed on the helical thickenings. The involvement of MTs in the formation of bordered pits and helical thickening is discussed.

Wood Anatomy of Trees and Shrubs from China. VI. Magnoliaceae

The wood anatomy offive genera of Magnoliaceae (59 native species, 2 introduced species) of China is described. Although the wood anatomy of this family is rather homogeneous, it is possible to identify most specimens to genus. Magnoliaceae wood from China is characterised by diffuse-porosity, scalariform to opposite vessel wall pitting, scalariform perforations with few bars or in some Magnolia species simple perforations, ground tissue fibres with distinctly to minutely bordered pits, marginal parenchyma and heterocellular rays mostly with one marginal row of square/upright cells. Intervessel and vessel-parenchyma pits are almost exclusively opposite in the Liriodendroideae; they are almost exclusively scalariform in the Magnolioideae, except for Magnolia section Rhytidospermum in which pits are predominantly opposite. Although the wood anatomical characters more or less overlap between Magnolia and Manglietia, these genera are wood anatomically distinguishable. Wood anatomy is similar in the evergreen species of Magnolia and Michelia. Kmeria is the only genus in which crystals were observed. Taxa from the tropics to subtropics tend to have longer and wider vessel elements, and a lower vessel frequency than those from temperate provenances; oil cells in rays mostly occur in the taxa from tropical and subtropical provenances. Simple perforation plates are mostly present in the temperate taxa. Counter to trends for the dicotyledons at large, helical thickenings are more common in tropical species than in temperate species, and, when present, are usually not distinct in deciduous species.

Wood anatomy of the dicotyledons indigenous to New Zealand 22. Proteaceae

Abstract Wood anatomy of Toronia toru (A. Cunn.) L. Johnson & B. Briggs and Knightia excelsa R. Br. is described. Knightia is readily distinguished from Toronia by the festooned arrangement of vessels and axial parenchyma, fewer and wider vessels, markedly large rays, and absence from vessels of both helical thickenings and vestured pits. Growth-ring boundaries in Knightia are indicated by marked noding of wide rays. Fine helical thickenings are present in some fibre-tracheids of Toronia and Knightia. Fusiform parenchyma cells lacking storied structure are recorded in Toronia. Vestured pits are recorded in vessels and fibre-tracheids of several Australian species of Persoonia sensu stricto, and the segregate genera Acidonia and Pycnonia.

Response of Differentiating Tracheids to Stem Inclination in Young Trees of Taxus Cuspidata

Differences in response among differentiating tracheids to the stimulus of stem inclination were examined at three heights in stems of young trees of Taxus cuspidata Sieb. et Zucc. A change in the orientation of the helical cell wall thickenings from an S- to a Z-helix with a simultaneous absence of an S3 layer were the first anatomical responses to appear. These changes first occurred in differentiating xylem on the underside of the upper segment of the stem after 4 days inclination. The gravistimulus for compression wood formation was transmitted basipetally within the stem as the tilting period was increased. After 10 days, the xylem on the underside of the upper segment of the stem contained five mature cells with a Z-helix, indicating that deposition of the thickenings required 2 days. The present results suggest that the rate of cambial division and xylem differentiation differs longitudinally in an inclined stem. For Taxus cuspidata, a change in the orientation of the helical thickenings should be a useful marker for deciding whether or not the differentiating cells have perceived the stimulus for compression wood formation.

Wood Anatomy of the Bignoniaceae, with a Comparison of Trees and Lianas

The secondary xylem anatomy of trees and lianas was compared in the family Bignoniaceae. General descriptions of the family and the six woody tribes are provided. Lianas belong to the tribes Bignonieae, Tecomeae and Schlegelieae, and most have ve.ssels of two distinct diameters, many vessels per unit area, large intervascular pits, septate fibres, large heterocellular rays often of two distinct sizes, scanty paratracheal and vasicentric axial parenchyma and anomalous growth. Conversely, trees, which belong to the tribes Coleeae, Crescentieae, Oroxyleae and Tecomeae generally have narrower vessels in one diameter class, fewer vessels per unit area, smaller intervascular pits, non-septate fibres, small homocellular rays, scanty paratracheal, aliform or confluent parenchyma, and none exhibits anomalous growth. The majority of both trees and Hanas possess growth rings, are diffuse-porous, have non-solitary vessels which lack helical thickenings, and few have apotracheal parenchyma or storied structure. All species have alternate intervascular pitting and simple perforation plates.

ENDOTHECIUM IN IRIDACEAE AND ITS SYSTEMATIC IMPLICATIONS.

An examination of the endothecial thickenings in 44 species of Iridaceae, selected from the four subfamilies and all major tribes, provides useful information about generic and tribal relationships in the family. U-shaped thickenings occur in Nivenioideae and Iridoideae-Sisyrinchieae, the latter the least specialized tribe of its subfamily. The occurrence of helical thickenings in all members examined of Iridiodeae tribes Irideae, Mariceae, and Tigridieae (a putatively monophyletic group) and Ixioideae is consistent with the recognition of these two lines as distinct taxa based on anatomical, morphological, phytochemical, and in the case of Ixioideae, palynological criteria. Baseplate thickenings are restricted to Patersonia. However, the shrubby Cape genera-Nivenia, Klattia, and Witsenia-have U-shaped thickenings which show a tendency for the bars on the inner periclinal cell walls to anastomose, suggesting a trend towards the baseplate condition in Patersonia. This accords with a suggested relationship between these genera, based on anatomical and flavonoid similarities. The pattern of variation in endothecial thickenings in Iridaceae is consistent with the phylogeny proposed by Goldblatt (1990). The distribution of thickening types within the family does not make it possible to polarize this character, but the most parsimonious interpretation assumes that U-shapes are basic. However, in at least some other monocotyledonous families the pattern suggests that U-shaped thickenings are derived from helices.

Cladistic Analysis of Patterns of Endothecial Thickenings in the Poales/ Restionales

The three-dimensional structure of the endothecial thickenings in the anthers was investigated in 87 species from 70 genera, chosen to provide representative coverage of the families Cyperaceae, Restionaceae, Anarthriaceae, Ecdeiocoleaceae, Centrolepidaceae, Joinvilleaceae, Flagellariaceae, Poaceae, Xyridaceae, and Eriocaulaceae. There is complex variation in the patterns of endothecial thickening: the Eriocaulaceae, Flagellariaceae, and most Poaceae have thickenings with a complete baseplate; the Cyperaceae and most of the Restionaceae are characterized by helical thickenings; some genera in the Bambusoideae have annular thickenings; and U-shaped thickenings occur in the Xyridaceae and Eriocaulaceae and in some Poaceae and Restionaceae. Joinvillea and Ecdeiocolea have unique thickening types. Endothecial characters were subjected to cladistic analysis. Including endothecial characters in an existing cladogram of the group indicates that there is no single, well-corroborated cladogram available for the Poales/Restionales.

CLADISTIC ANALYSIS OF PATTERNS OF ENDOTHECIAL THICKENINGS IN THE POALES/RESTIONALES.

The three-dimensional structure of the endothecial thickenings in the anthers was investigated in 87 species from 70 genera, chosen to provide representative coverage of the families Cyperaceae, Restionaceae, Anarthriaceae, Ecdeiocoleaceae, Centrolepidaceae, Joinvilleaceae, Flagellariaceae, Poaceae, Xyridaceae, and Eriocaulaceae. There is complex variation in the patterns of endothecial thickening: the Eriocaulaceae, Flagellariaceae, and most Poaceae have thickenings with a complete baseplate; the Cyperaceae and most of the Restionaceae are characterized by helical thickenings; some genera in the Bambusoideae have annular thickenings; and U-shaped thickenings occur in the Xyridaceae and Eriocaulaceae and in some Poaceae and Restionaceae. Joinvillea and Ecdeiocolea have unique thickening types. Endothecial characters were subjected to cladistic analysis. Including endothecial characters in an existing cladogram of the group indicates that there is no single, well-corroborated cladogram available for the Poales/Restionales.

Xylotomical studies of some Boraginaceae

Xylotomical features ofTournefortia rugosa, Tournefortia caracasana, Heliotropium angiospermum andMallotomia gnaphalodes of the family Boraginaceae have been described with emphasis on vessel elements, fibrous elements, parenchyma and vascular rays. Presence of helical thickenings in the narrow vessels, septate fibres, siliceous granules, crystals, tannins and druses in the ray cells are some of the interesting features met with in these members.

Occurrence of Helical Thickenings on the Vessel Element Walls of Dicotyledonous Woods

Occurrence of Helical Thickenings on the Vessel Element Walls of Dicotyledonous Woods

Wood Anatomy of Myoporaceae: Ecological and Systematic Considerations

Quantitative and qualitative features are presented for 28 collections of three genera (Bontia, Eremophila, Myoporum); data on Oftia are also included since it is sometimes referred to Myoporaceae. Wood of all Myoporaceae represents variation on a basic plan: woods diffuse porous or semi-ringporous; vessels with simple perforation plates; lateral wall pits of vessels alternate and circular, with grooves interconnecting some pit apertures; vessels grouped to various degrees into radial multiples; imperforate tracheary elements all fiber-tracheids with pit cavities 1-5 μm in diameter (wider on contacts with ray cells), nonseptate; axial parenchyma vasicentric scanty plus, in some species, tangential para tracheal bands (sometimes terminal); rays multi seriate plus uniseriate (uniseriate almost exclusively in two species of Eremophila); ray cells procumbent exclusively, upright and square in uniseriate rays and in tips of multiseriate rays; rays storied in some species of Eremophila, axial parenchyma variously storied; crystals present in ray cells of some species of Eremophila and in fibers of E. polyclada; amorphous deposits and starch often present in parenchyma. Ofiia differs from Myoporaceae by having: septate libriform fibers rather than fiber-tracheids; large pits on vessel walls; axial parenchyma nearly absent; and erect cells predominant in rays. Oftia may be placed in Scrophulariaceae. Leucophyllum differs from Myoporaceae by having: helical thickenings in vessels; vasicentric tracheids transitional from vascular tracheids; scarce axial parenchyma; and erect cells predominant in rays. Leucophyllum may be excluded from Myoporaceae. Wood anatomy ofMyoporaceae shows relationship between Myoporaceae, Scrophulariaceae, and Gesneriaceae, and is also indicative of derivation from woody ancestors. Wood of Myoporaceae reflects xeromorphy, especially in Eremophila, but the foliar apparatus may partially preempt the role of wood in promoting safety, which is connoted by growth rings, narrow and numerous vessels, and grouped vessels.

Wood Anatomy of Coriariaceae: Phylogenetic and Ecological Implications

A B S T R A C T Stems of four species of the Australian family Tremandraceae furnished sufficient material for analysis of wood anatomy. Presence of simple perforation plates on vessel elements, occurrence of libriform fibers (some septate), tendency toward vasicentric parenchyma, presence of crystalliferous axial parenchyma strands, presence of crystals singly in ray cells, and occurrence of amorphous deposits in parenchyma are all features in which Tremandraceae resemble Pittosporaceae. Wood anatomy tends to support a rosoid rather than a sapindalean, rutalean, or polygalalean affinity for Tremandraceae, although wood is only a preliminary indicator. By the use of numerical indices as well as such indicators as helical thickening and presence of vascular tracheids, wood of Tremandraceae is shown to be highly xeromorphic. The genus Tremandra may represent a secondary entrant into wet forests of southwestern Australia; it clearly is not relict from mesic ancestry. THE FAMILY Tremandraceae is endemic to Australia and is especially well represented in southwestern Australia, where the species in the present study were collected. The family consists of three genera: Platytheca (two species), Tetratheca (about 16 species), and Tremandra (two species). Tetratheca consists of subshrubs, branched from the base or from below soil level. The numerous innovations are mostly annual, and therefore accumulate little wood; the caudex and roots consist of much-contorted, soft, fragmented and atypical xylem, and such wood was not deemed suitable for analysis here. The only species of Tetratheca which could provide sufficient suitable wood for study is an undescribed species collected in the Tuttanning Reserve. This species, which will be described by an Australian botanist monographing the family, bears a superficial resemblance to T. harperi F. Muell., and the Tuttanning plants may be found annotated thus in certain herbaria. Tetratheca harperi is native to a quite different area, north of Southern Cross, W.A. The two species of Tremandra occur in the most mesic part of Western Australia, the southwesternmost corner. Both, however, tend to be found in forest openings on disturbed soil. Tremandra diffusa R. Br. has numerous wiry, sprawling stems from a small knotty caudex, the wood of which was unsuitable for sectioning. Tremandra stelligera R. Br. could almost be called an herb because of limited wood accumulation, but some

Helical Thickenings in Normal and Compression Wood of Some Softwoods

Compression wood in some softwoods having helical thickenings on the inner surface of normal wood tracheids were examined using a scanning electron microscope. Helical thickenings of Taxus, Torreya and Cephalotaxus have narrow bases, and are loosely attached to the innermost layer of the secondary wall, while those of Pseudotsuga, Picea and Larix have broad bases blended tightly with the microfibrils of the S3 layer in normal wood. The transition from normal to compression wood entails a preservation of the thickenings in Taxus, Torreya and Cephalotaxus, while they are replaced by helical ridges and cavities in Pseudotsuga, Picea and Larix. The direction of helical thickenings gradually changes from an S- to a Z-helix, or a Z- to an S-helix in the course of the transition from normal to compression wood, or vice versa in Taxus, Torreya and Cephalotaxus. Helical checks never occur in these species. In Pseudotsuga, however, helical thickenings can be deposited as an additional layer on the helical ridges. The results obtained in the present investigation revealed that the orientation of the thickenings did not always coincide with that of the innermost microfibrils of the secondary wall layers, indicating that helical thickenings may be considered as a layer independent of the secondary wall.

A Comparison of the Ecological Wood Anatomy of the Floras of Southern California and Israel

A comparison is made between ecological trends in wood anatomy found in southern California and Israel and adjacent regions. Trends for type of vessel perforation, vessel member length and the occurrence of helical thickenings show striking parallels. Characters like vessel diameter and frequency and incidence of (fibre-)tracheids show only weakly similar trends. Vessel grouping and ring-porosity do not show any parallel in the data for southern California and Israel. The differences between the two floras can largely be attributed to different floristic composition and the alternative possibilities for safe and efficient xylem sap transport and drought resistance in different taxa.

Comparative morphology of the vessel elements in the woods ofPseudopanaxC. Koch (Araliaceae)

Abstract Vessel elements in the woods of the fourteen species of Pseudopanax indigenous to New Zealand were examined using scanning electron microscopy. The occurrence of the vestured (or warty) layer, helical thickenings, various perforation plate types, and the type and distribution.of vessel pits confirmed the validity of the species groups proposed by Philipson (1971) and also indicated that the presence or absence of a vestured layer may be a useful diagnostic feature in taxonomic studies.

The Occurrence of Scalariform Perforation Plates and Helical Vessel Wall Thickenings in Wood of Myrtaceae

The occurrence of multiple perforation plates and helical wall thickenings in vessel elements of 144 species (plus 12 varieties and 2 hybrids) in 53 genera of Myrtaceae was extensively explored. Scalariform perforation plates occur in 40 species (plus 1 hybrid), in Luma, Myrceugenia, Myrteola, Ugni, and in the monotypic Myrtastrum rujo-punctatum, Neomyrtus pedunculata, and Tepualia stipularis. Ugni candollei also has foraminate (i.e., sieve-like) perforation plates. Helical wall thickenings occur in 33 species (plus 1 hybrid), in Acmena, Austromyrtus, Myrceugenia, Myrcia, Myrcianthes Psidium, Xanthomyrtus, and in Myrtus communis. Most of these records are new. The speeies with exclusively scalariform perforation plates (in Luma, Myrteola, Neomyrtus, and Ugni) are from cool mesic habitats; those with mixed simple and multiple perforation plates are also largely cool mesic but show a somewhat greater diversity of habitats. Myrtaceae with exclusively simple perforation plates predominate in all habitat types. Helical wall thickenings occur sporadically throughout the distributional range ofthe family. However, tropical species tend to have weaker helical thickenings than the subtropical and temperate species exhibiting them. The possible functional significance of these ecological tendeneies is discussed. It is hypothesised that multiple perforation plates were retained in some cool mesic Myrtaceae because of a lack of strong selective pressure to eliminate them from this type of environment, rather than that they were retained because of adaptive significance in trapping embolisms. The systematic and diagnostic value of multiple perforation plates and helical wall thickenings is also discussed. Scalariform plates are largely confined to related genera in Myrtoideae; Tepualia is the only representative from Leptospermoideae. Helical wall thickenings are only of limited diagnostic and systematic value above the species level.

A Note on Vestures on Helical Thickenings

A Note on Vestures on Helical Thickenings

WOOD ANATOMY OF BUBBIA (WINTERACEAE), WITH COMMENTS ON ORIGIN OF VESSELS IN DICOTYLEDONS

Quantitative and qualitative features of wood anatomy are reported for ten collections of seven species of Bubbia. Variations on the basic plan for Winteraceae can be interpreted in terms of taxonomic and ecological distinctions. Tracheid length is correlated with plant size and habit: tracheids are shortest in shrubs. Tracheid wall thickness and ray cell wall thickness distinguish species. Ray cell procumbency and multiseriate ray width increase with age. Growth rings occur only in a species from stream margins. SEM studies reveal absence of a warty layer within tracheids. Helical thickenings are absent. Presence of these two features in Pseudowintera may be correlated with the cool temperate habitats of that genus. Overlap areas of tracheids in Bubbia show various degrees of scalariform pitting, ranging from none (B. semecarpoides) to abundant presence (B. balansae). Perforation‐like pits in tracheids of the latter prove, with SEM studies, to have pit membranes containing porosities less than 1 μm in diameter. Scalariform pitting on overlap areas is absent in earlier secondary xylem and increases during later secondary xylem. Scalariform lateral wall pitting can occur in abnormally wide tracheids formed after pauses in cambial activity. These facts show that primitive dicotyledon woods like those of Bubbia can activate genetic information for scalariform end wall patterns and lateral wall pitting such as primitive vessels show without the intervention of paedomorphosis. Paedomorphosis in dicotyledon woods is held still to apply only to special herbaceous and herblike growth forms, not to primarily woody plants. Progenesis (in xylem, loss of secondary xylem) is not held to be necessary to account for the scalariform patterns seen in tracheary elements of primitive dicotyledons. Reasons are given for rejection of the hypothesis that Winteraceae and other woody dicotyledons (Amborella, Sarcandra, Tetracentron, Trochodendron) are secondarily vesselless.

Wood Anatomy of Buxaceae: Correlations with Ecology and Phylogeny

Summary The family Buxaceae consists of four genera, with the desert shrub Simmondsia dubiously included in the family as a fifth genus. Styloceras (Andean rain forest) has the most mesomorphic and primitive wood features, followed by Sarcococca and then by Buxus, which can be grouped closely with Notobuxus in terms of wood anatomy. Pachysandra was excluded from this study because of its essentially herbaceous habit. For a small family, Buxaceae have a wide span in expression of wood features. Characters in Buxaceae s.s. which show a range within the family probably explainable in terms of ecology include vessel element length, number of vessels per mm2, vessel diameter, number of bars per perforation plate, presence or absence of helical thickenings in vessels and tracheids, and presence or absence of growth rings. The woods in the family can be ranked as highly mesic (Styloceras, Sarcococca) to moderately mesic (Buxus, Notobuxus), with a few species in the latter pair of genera notably more mesomorphic in wood construction. Retention of scalariform perforation plates throughout Buxaceae s.s. may be due to compensatory low transpiration capabilities of the foliage, which may have very thick cuticles and tend toward microphylly. Features which are susceptible to evolutionary interpreation but which do not bear as direct a relationship to ecology include ratio of tracheid length to vessel element length, presence of tracheids with fully bordered pits, degree of aggregation of axial parenchyma cells (diffuse, diffuse-in-aggregates, abaxial) and degree of cellular heterogeneity in ray histology. The ray types of Sarcococca reflects a type of juvenilism, and scarcity of axial parenchyma in the genus also seems related to innovation of numerous shoots, each with limited duration. Simmondsia differs from Buxaceae s.s. in its desert habitat, its successive cambia, and its anemophily. Distinctive features of wood anatomy (lack of acial parenchyma, juvenilism in ray histology, and presence of very short vessel elements with helical thickenings) can be attributed to the first two factors. No features of wood anatomy clearly rule out relationship to Buxaceae. Presence of tracheids in wood of Simmondsia may be related to the high selective value for tracheids in a desert environment; this feature (and the encyclocytic stomata) suggest affinity to Buxaceae, even if the genus is segregated in Simmondsiaceae. Buxaceae have been claimed to be related to four major groups of dicotyledons: Celastrales, Euphorbiales, Hamamelidales, and Pittosporales. Of these, Euphorbiales shows the least degree of resemblance to Buxaceae in terms of wood anatomy. The placement of the isolated Madagascan genus Didymeles may be related to the problem of placement of Buxaceae, and is discussed in this context.