Protoxylem Groups Research Articles

Diodonopteris virgulata sp. nov., a climbing fern from the early Permian Wuda Tuff Flora and its paleoecology

Botryopteridaceae, characterized by an omega-shaped foliar trace, is one of the best known late Paleozoic fern families with frequent occurrence in the Carboniferous of Euramerica and recent recognition in Permian deposits of Gondwana and Cathaysia. Diodonopteris is a recently established botryopterid genus based on coal-ball material from the lower Permian Taiyuan Formation of Shanxi Province, China. Here, a new species of Diodonopteris is described based on an anatomically preserved specimen from the well-known early Permian Wuda Tuff Flora in the Wuda Coalfield of Inner Mongolia, China. Diodonopteris virgulata sp. nov. is similar to the type species D. gracilis in the marginal position of protoxylem groups but differs from the latter in having a simpler cortex and a more expanded xylem strand. The two known Diodonopteris species share several characteristics considered ancestral among botryopterids, including strand shape, mode of pinna trace divergence, weak pinnule lamination, and a laminar wing on the rachis, as is consistent with Diodonopteris sitting outside any of the derived sublineages within Botryopteris. D. virgulata is confirmed to be a climber by direct preservation with the host. Moreover, the host plant is also evidenced to be a climber. The repeated preservation of the dual-climbing phenomenon in this swamp forest signals the complexity of early Permian ecosystems.

Vincetoxicum indicum (Burm.f.) Mabb. - a case of transient abnormal secondary thickening in stem

Vincetoxicum indicum (Burm.f.) Mabb. (Syn. Tylophora indica (Burm.f.) Merr., T. asthmatica W. &A.), an important twining medicinal plant of India, was found to show a transient anomalous secondary thickening to facilitate the twisting of stem around a support. The very young stem had a continuous primary xylem cylinder, the protoxylem of which differentiated to two large bundles on the opposing sides and many smaller bundles in between. In the initial stages of maturation, the cambium outside the two large protoxylem groups behaved abnormally in producing more phloem outwards and little or no secondary xylem inwards to produce two wedge shaped phloem groups on opposite sides. The production of crescent shaped secondary xylem on the other two sides which fell at a right-angled plane resulted in bulging of these sides away from the anomalous cambium to create a rectangular stem having two broad sides which were used as the facing sides of stem against a support. As soon as the twisting nature was established, the anomaly was reversed and the anomalous cambial patches started behaving normally to produce a complete ring of secondary xylem. As this abnormal behaviour happened only during the twisting of stem, this is considered as an adaptational anomalous secondary thickening.

Heterorhizy and fine root architecture of rabbiteye blueberry (Vaccinium virgatum) softwood-cuttings.

All fine root systems consist of individual fine roots. Individual roots have morphological, anatomical, and functional heterogeneity (heterorhizy). Heterorhizy plays crucial roles in plant ecosystems. However, in many species, the heterorhizy and fine root system architecture based on individual root units are unclear. This study investigated heterorhizy along the root system architecture of Vaccinium virgatum Ait (rabbiteye blueberry) softwood-cuttings (propagated from annual shoots in growing season) using protoxylem groups (PGs), a classification according to the number of protoxylem poles, as an indicator of individual root traits. Individual roots of rabbiteye blueberry varied from monarch to heptarch. The frequency of roots with larger number of PGs decreased but those with smaller number of PGs increased from adventitious roots toward lateral roots with different branching levels. This architecture were stable among cultivars, collecting position of the cuttings, or indole acetic acids treatment. Individual root sizes and secondary growth were positively correlated with the PGs. These results indicate that branching itself strongly and broadly controls individual root traits. The individual roots were classified into two types: monarch and diarch roots with small size and lacking secondary growth (thought to be hair roots in core Ericaceae) and triarch or more PG roots with large size and showing secondary growth. These heterogeneous individual roots responded differently to the experimental factors. In particular, elongation of the large roots significantly contributed to increased total root length. These results mean that heterorhizic plasticity is a determinant of root system development and heterorhizic variation exists even under practical cutting condition. In conclusion, we demonstrated heterorhizy of rabbieye blueberry cuttings based on the strong relationships of PG, individual root morphology and growth potential, and root system architecture. This study also supports strong connection between root morphology and functional roles intermediated by the PG.

Changes in the anatomy, morphology and mycorrhizal infection of fine root systems ofCryptomeria japonicain relation to stand ageing

Biomass allocation to fine roots often increases under soil nutrient deficiency, but the fine root biomass does not often increase in old stands, even under nutrient limitation. Therefore, in old stands, the morphology, anatomy, branching architecture and mycorrhization of fine roots may compensate efficiently for nutrient acquisition by the low fine root biomass. In this study, changes in the morphology, anatomy and arbuscular mycorrhizal infection at each branching position of fine root clusters were evaluated in relation to stand age. A chronosequence (6–90 years of age) of stands in a Cryptomeria japonica D. Don plantation was used for these analyses. The fine root size parameters, such as length, weight and tip numbers of fine root clusters, increased with stand age. The specific root tip length (SRTL) decreased with increasing stand age, suggesting that the allocation to root active portions decreased with stand age. From the anatomical observation, the ephemeral root tips increased with stand age, suggesting that root tip turnover within a root cluster was high in old stands. The proportions of proto-xylem groups among branching positions indicated that the life cycles in branching hierarchy should be clearer in old stands than that in younger stands. The increasing in the mycorrhizal infection of root tips in old stands should enhance the root tip absorptive functions. The SRTL was correlated with the wood/needle ratio, suggesting that carbon limitation as the stand ages may result in decline of carbon allocation to maintain active root tips. However, increasing of the ephemeral tips and mycorrhizal infection rates may compensate the declines of tip allocation in old stands.

Diodonopteris, a new genus of the Paleozoic leptosporangiate fern family Botryopteridaceae, from the lower Permian of Shanxi Province, North China

Anatomically preserved botryopterid specimens from Cisuralian (early Permian) aged coal balls in Shanxi Province, North China are investigated. Stems are relatively small, branch dichotomously, and possess a haplostele with metaxylem tracheids showing uniseriate scalariform thickenings. Protoxylem groups are associated with the forming of the petiolar trace, and a parenchyma plate appears in the process of separating petiolar traces. The cortex consists of three parts, with inner and middle parenchymatous zones and an outer sclerenchymatous zone. Stems are radially organized and bear helically arranged petioles. Petioles extend from the stems in various orientations while adventitious roots extend through the cauline cortex perpendicular or oblique to the stem. Associated rachides are D-shaped in cross section and the xylem is slightly to conspicuously adaxially curved with 1 protoxylem ridge at each lateral margin. Differences with previously known genera of Botryopteridaceae lead to creation of new genus, Diodonopteris gracilis Ma et al. gen. nov. et sp. nov. that demonstrates features that overlap to some extent with those of previously known genera within Botryopteridaceae. The habit and growth forms of D. gracilis are considered. D. gracilis represents by far the best known plant of Botryopteridaceae recognized from the Cathaysian Flora.

Rhabdoxylon taiyuanense n. sp.: A new botryopterid fern from the Lower Permian of Shanxi Province, North China

This paper described a new early leptosporangiate fern occurring in the Lower Permian coal balls from Shanxi Province, North China. The fossil materials include stems, attached and detached petioles and roots, belonging to a same kind of plant. Stems are relatively small in diameter and branch dichotomously. They possess a haplostele with metaxylem tracheids decreasing outward in diameter and showing uniseriate scalariform thickenings. There are no distinguished protoxylem groups in the xylem cylinder. Cortex is parenchymatous and can be divided into three zones according to cell size. Petiolar traces bear different shapes in cross section and show a spiral diverging sequence. Petioles are circular in cross section and cortical cells are much smaller than those of stems. Petiolar traces and petioles possess a single protoxylem group at the adaxial side of the xylem strand. Root traces originate from the cauline stele and go through the cortex in a way perpendicular or oblique to the cauline stele. These characters show great similarities to the genus Rhabdoxylon but are not consistent with its any known species, so it is necessary to create a new species Rhabdoxylon taiyuanense n. sp. for the present plant. The new species probably possesses an upright habit. This is the first report of the existence of the genus Rhabdoxylon in the Cathaysian Flora. The discovery of a new type of the Palaeozoic leptosporangiate fern in China has led to reevaluation of the systematic relationships among species of the Botryopteridaceae.

Which is the best indicator for distinguishing between fine roots with primary and secondary development in <i>Cryptomeria japonica</i> D. Don: Diameter, branching order, or protoxylem groups?

Which is the best indicator for distinguishing between fine roots with primary and secondary development in <i>Cryptomeria japonica</i> D. Don: Diameter, branching order, or protoxylem groups?

Contrasting the morphology, anatomy and fungal colonization of new pioneer and fibrous roots

Not all roots born as first-order branches are the same and this has important consequences for overall function. We hypothesized that, compared with fibrous roots, pioneer roots are built to live longer at the expense of absorptive capacity. We tested this hypothesis by investigating pioneer and fibrous roots in their first 14 d of life in the arbuscular mycorrhizal tree species: Acer negundo, Acer saccharum, Juglans nigra, Liriodendron tulipifera and Populus tremuloides. Root observations were made with root-access boxes that allowed roots to be sampled at known ages in field-grown trees. Compared to fibrous roots, pioneer roots had larger diameter, lower specific root length, greater average length and a lack of mycorrhizal or nonmycorrhizal fungal colonization. Pioneer roots < 14 d old had more layers of hypodermis with a lower percentage of putative passage cells and more protoxylem groups than similar age fibrous roots. Our results suggest that pioneer roots are constructed for defense against biotic and abiotic challenges, exploration of soil distal to the stem, high fibrous root branching and secondary development with high axial hydraulic conductivity at the expense of mycorrhizal colonization and high absorptive capacity for water and nutrients.

Life cycles of individual roots in fine root system of Chamaecyparis obtusa Sieb. et Zucc.

Recent studies have remarked on differences in the life cycles of individual fine roots. However, the dynamics of individual roots with different life cycles, such as ephemeral and perennial, during root system development are still unknown. We examined individual roots during fine root system development in a mature stand of Chamaecyparis obtusa Sieb. et Zucc. (Cupressaceae) using the sequential ingrowth core method and an anatomical method. The visual classification, i.e., orange, red, brown, intact dead, and fragmented dead, of fine roots corresponded well with the anatomical classification. Orange and red roots contained passage cells, and brown roots contained cork cambium. The proportions of protoxylem groups differed among visual classes. Brown secondary roots were mainly triarch (43%) and tetrarch (40%) and rarely diarch (12%), whereas fragmented dead roots, which constituted more than 95% of the dead roots, were mainly diarch (67%). These results imply that triarch and tetrarch roots tend to form secondary roots, whereas diarch roots tend to become dead roots without secondary growth. Using the numbers of root tips and clusters, root system development could be classified into three stages: colonization, branching within the root system, and maintenance. During the colonization stage, mainly triarch and tetrarch roots, which tend to be secondary growth, invaded ingrowth cores. During the branching stage, primarily diarch roots, which tend to be ephemeral, emerged. Fine root system development involved the recruitment of different individual roots during the life cycle depending on the growth stage.

Dynamics of heterorhizic root systems: protoxylem groups within the fine‐root system of Chamaecyparis obtusa

To understand the physiology of fine-root functions in relation to soil organic sources, the heterogeneity of individual root functions within a fine-root system requires investigation. Here the heterogeneous dynamics within fine-root systems are reported. The fine roots of Chamaecyparis obtusa were sampled using a sequential ingrowth core method over 2 yr. After color categorization, roots were classified into protoxylem groups from anatomical observations. The root lengths with diarch and triarch groups fluctuated seasonally, whereas the tetrarch root length increased. The percentage of secondary root mortality to total mortality increased with increasing amounts of protoxylem. The carbon : nitrogen ratio indicated that the decomposability of primary roots might be greater than that of secondary roots. The position of diarch roots was mostly apical, whereas tetrarch roots tended to be distributed in basal positions within the root architecture. We demonstrate the heterogeneous dynamics within a fine-root system of C. obtusa. Fine-root heterogeneity should affect soil C dynamics. This heterogeneity is determined by the branching position within the root architecture.

Reconstruction of the frond of Laceya hibernica, a Lyginopterid pteridosperm from the uppermost Devonian of Ireland

The frond of Laceya hibernica May et Matten was studied using anatomical/morphological features and statistical analyses. Quantitative and qualitative characters were used to identify and determine position in the frond of isolated fragments. Features examined were: cross-sectional diameter and height; cross-sectional areas of the entire axis, vascular tissues and sclerenchymatous tissue; number of protoxylem groups; and shape of vascular tissue. The frond was at least twice compound with a single dichotomous forking of the primary rachis. Alternate pinnae occurred prior to bifurcation of the primary rachis and along the secondary rachises. Anatomically, the primary rachis had three regions: the base—with a V-shaped vascular strand with 8–12 protoxylem groups; the mid-section—with a W-shaped strand with 10–16 protoxylem groups; and immediately below the bifurcation—with two V- or U-shaped vascular strands with 3–8 protoxylem groups each. Secondary rachises were characterized by a V- or J-shaped vascular strand with 4–8 protoxylem groups. Pinna traces were bilobed to arcuate with 2–4 protoxylem groups. Protoxylem maturation was mesarch throughout the frond. A well-developed sparganum outer cortex occurred in the rachises and was reduced or lacking in pinnae and pinnules. Reconstructions of the frond were assembled. Comparisons were made between the frond of Laceya and the fronds of members of the Lyginopteridales sensu lato, Stenokoleales and Aneurophytales.

Millerocaulis richmondii sp. nov., an osmundaceous fern from Mesozoic strata near Little Swanport, Tasmania, Australia

A permineralised rhizome from Mesozoic strata south of Little Swanport, Tasmania, represents a new species of Millerocaulis (M. richmondii).Its stem is 6 x 7 mm across and is surrounded by adhering leaf bases with each having a stipular expansion typical of the Osmundaceae. The xylem of the ectophloic siphonostele comprising this stem is dissected by leaf gaps and consists of 14 xylem strands in its cylinder.Twenty leaf traces occur in a transverse section of its cortices. The xylem of its leaf traces and petiolar vascular strands is generally curved adaxially with a single protoxylem cluster being median on the trace. This proroxylem cluster bifurcates into two protoxylem groups immediately after leaving the stem and upon entering the petiole. The sclerotic ring of the petiole base is uniform in width and cell-wall thickness. A mass of sclerenchyma present in the adaxial concavity of the petiolar vascular strand expands at higher levels of the petiole until it fills the concavity of the strand and becomes immediately adjacent to the sclerotic ring. A large, round cellular mass of sclerenchyma occurs in the stipular expansions midway between their sclerotic rings and their tips. Millerocaulis richmondii is an additional species in the family Osmundaceae which was very abundant in Tasmania during mid-Mesozoic time.

A new species of Heterangium from the Illinois basin of North America

A Heterangium specimen from the Illinois Basin exhibits a prominent periderm and distinct exarch protoxylem groups from which leaf traces arise individually. As a trace passes to a leaf it remains single but is bilobed for as far as it can be followed into a winged petiole. These features place the new species in the subgenus Heterangium. The specimen lacks the sclerotic plates and sparganum outer cortex present in other species. Certain aspects of stelar structure suggests that Heterangium represents a pteridosperm lineage that retained the protostelic condition from ancestors that produced other lineages exhibiting various degrees and types of longitudinal stelar dissection.

10.—Triradioxylon—a New Genus of Lower Carboniferous Petrified Stems and Petioles together with a Review of the Classification of Early Pterophytina

SynopsisTriradioxylongen. nov. is erected for petrified stems and petioles in which the primary xylem has a triradiate form and possesses protoxylem at the ends of the arms and in the central region. Secondary xylem is dense and composed of small tracheids having multiseriate bordered pits on all walls. Rays are narrow and high. The cortex has sclerotic nests and radial bands of fibres (sparganum structure).In the type speciesT. primaevumsp. nov. the petioles are borne 5–6 cm apart in a phyllotactic spiral of ⅓ on a stem about 1 cm (or more) diameter. The petiole is swollen at its base (about 8 mm diameter) and very gradually tapers to about 2 mm in the rachis which has not been seen to dichotomise. The length of petiole up to the first pinna may exceed 10 cm. Pinnae arose alternately and themselves branched. The T-shaped petiolar bundle has two protoxylem groups at the end of each arm and the central protoxylem divided into three in the rachis.Two detached rachises which cannot be assigned with certainty toTriradioxylon primaevumare placed in the genusLyginorachisand namedL. whitadderensissp. nov. In these the T-shaped vascular bundle is slightly larger than that in the rachises ofT. primaevumand the ends of the transverse arms are wider and may possess three protoxylem groups.The rachises in bothT.primaevumandL. whitadderensisbear alternate triarch pinna-traces but inL. whitadderensisa pair of sub-opposite monarch pinna-traces is also present.Triradioxylonis classified along withButeoxylonin the family Buteoxylonaceae placed tentatively asincertae sedisin the Pteridosperms although showing some affinity withAneurophytonin the Progymnospermopsida.

Rodeites sahni reinvestigated II

The paper describes the structure of a 5 cm. long petiole bearing five Rodeites sporocarps one above the other in a row, collected from the Mohgaonkalan beds of the Deccan Intertrappean Series of India. It shows in T.S. a well-defined epidermis, aerenchymatous cortex and a central angular horse-shoe shaped robust vascular strand. On comparison with petioles of Marsilia, Pilularia and Regnellidium it is observed that the present petiole is different from them in thickness, arrangement of vascular tissues and in the number of protoxylem groups.&#x0D; Eleven indusial septae are seen clearly in one of the sporocarps. They are attached to the inner side of the sporocarp wall.&#x0D; The petiole bearing sporocarps and sporocarp with eleven indusial septae are being recorded here for the first time. Observations in this paper support the previous study of Rodeites sporocarps by the authors indicating that Rodeites was not identical with Regnellidium. but was an extinct fourth genus of Marsileaceae showing more resemblance to Marsilea than to Regnellidium. A new species Rodeites polycarpa is created in this paper.

IV.—Some Specimens of Protoclepsydropsis and Clepsydropsis from the Calciferous Sandstone Series of Berwickshire

SynopsisProtoclepsydropsis kidstoni (Bertrand) Hirmer is a small fossil fern with a slender stem about 3 mm. diameter bearing petioles of a Clepsydropsis type in a ⅖ phyllotaxy.Larger isolated Clepsydropsis petioles from the same rocks probably belong to a larger related plant. In these the petiolar bundle is sometimes oval in cross section with protoxylem groups nearer one tangential surface. Occasionally roots are borne on these petioles. A resemblance to the petioles of Asterochlœna laxa Stenzel is pointed out.

Osmundites Sahnii sp. nov., a new species of petrified osmundaceous rhizomes from India

The paper describes a petrified osmundaceous rhizome discovered from near Bmdrabun m the Jurassic of the Rajmahal Hills, Bihar.&#x0D; The specimen made up of vertically growing leaf bases and roots, includes three stems in it. Each stem has a broad sclerenchymatous outer cortex, surrounding a narrow inner cortex. The stele consists of 50-70 individual strands arranged in a circle surrounding the sclerenchymatous pith. Most of the strands are continuous with one another. The medullary strands are absent. The C-shaped leaf traces are each enclosed in a sclerotid ring with several protoxylem groups. Several sclerenchymatous strands are found scattered in the pith of the trace as well as in the stipular wing. No sclerenchymatous tissue is noticed in contact with the stele of the leaf trace.&#x0D; The specimen differs from the other Jurassic species of Osmundites in the distribution of sclerenchymatous strands in the leaf bases.

スジヒトツバの形態学的研究, 特に葉について

Anatomical and morphological studies have been carried on the sporophytes, especially on the leaves, of Cheiropleuria bicuspis var. integrifolia from Hachijo Island. Gametophytes which persist imperfectly on some juvenile plants are also observed. There is an abundance of particular and primitive characteristics, such as, (a) the protostele showing a dorsiventrality in the dominant number of the protoxylem groups on its dorsal side ; (b) a marked dimorphism shown as the sterile and fertile leaves ; (c) firm and leathery laminas which are frequently bicusped at their tips and are provided with 4-6 parallel veins formed by repeated bifurcations of bundles of Marattia-type in the nor-articulated and wiry petiole, etc. An assortment of such characteristics of the sporophytes apparently shows an independent systematic position of Cheiropleuria among the Leptosporangiate ferns, and, thus, strongly supports the opinion of Nakai, who established an independent family Cheiropleuriaceae on the basis of some particular characteristics of the gametophyte.

IV—On rhexoxylon, bancroft—a triassic genus of plants exhibiting a liane-type of vascular organisation

In 1913 Dr. Bancroft instituted the generic nameRhexoxylonfor a portion of a petrified stem sent by Dr. Rogers, Director of the Geological Survey of South Africa, to Prof. Seward for investigation. The specimen was handed over to Dr. Bancroft, who, in a communication to the Linnean Society of London, gave a full account of its anatomy.Rhexoylon, as represented by the type-specimen, may be briefly described as follows:— The fragment of stem exhibits “parts of two more or less concentric series of vascular structures surrounding a large pith and embedded in a parenchymatous ground-mass,” which contains sclerotic nests and small vascular strands. The pith, in addition to sclerotic nests and small vascular strands, contains other structures, which are most probably of an anomalous nature. There is an inner ring or series of vascular structures, which were called, for convenience in description, “steles”; each consists of two portions of secondary wood, one centrifugal and the other centripetal, separated by a narrow zone of obliterated cells. The “steles” branch and rarely anastomose. Traces were described separating from the sides of the centripetal portions of the “steles” and taking a centrifugal course. Outside and opposite each member of this inner series is a mass of centrifugally-developed secondary wood, on the inner margin of which are numerous small protoxylem groups. The tracheids have bordered pits, arranged typically in two alternating series; the pits are flattened and in contact. The medullary rays are uniseriate. Tissue external to the xylem was described as phloem.

The Vascular Anatomy of the Seedling of Dioon edule

1. The vascular cylinder of the embryo is a protostele, but becomes a siphonostele in the seedling. It is very short and squarish in cross-section, one of the diagonals of the section being at right angles to the inner faces of the cotyledons, and the other parallel with them. Near each of the four corners is a group of protoxylem cells, the long diameter of whose section extends along the diagonal. 2. The four protoxylem groups extend downward to form the protoxylem of the root. 3. From each protoxylem group a foliar strand runs outward for a short distance and then branches, the branches separating at a wide angle and continuing outward until under the cotyledon, when they ascend it; the result is four strands for each cotyledon. The two protoxylem groups on the diagonal perpendicular to the inner faces of the cotyledons give rise to the two inner strands of each cotyledon; while the two protoxylem groups on the diagonal parallel with the inner faces of the cotyledons give rise to the two outer strands of the cotyledons, that is, one branch runs into the outer edge of the one and the other branch (from the same group) runs into the edge of the other cotyledon (opposite the first). 4. For each leaf or scale four strands leave the vascular cylinder at points not definitely located but well-distributed; two strands of each organ leave the cylinder approximately on the same side as the leaf for which they are destined, and run more or less directly through the cortex into the central or abaxial part of the petiole without branching; while the other two strands of each organ leave the cylinder approximately on the opposite side and describe a wide curve around it, the one in one direction and the other in the other, and finally ascend in the dorsal or adaxial part of the petiole, branching repeatedly. The girdle on the side toward which the spiral may be said to turn is generally the longer one. 5. When the cotyledonary vascular strands leave the vascular cylinder they are endarch, gradually become mesarch in their upward course, and finally approach the exarch condition. 6. The foliar vascular strands also are endarch at their separation from the vascular cylinder, and in their upward course become mesarch and finally exarch. In the very young leaf this transition extends through the whole base and petiole uniformly; but in the adult leaf it is comparatively rapid through the base up to the lower part of the petiole, where only a few centrifugal elements remain, and which remain uniform until in the rachis, where the transition is completed, so that in the pinna only centripetal xylem is left. 7. In the lower stretches of the foliar strands a considerable amount of the centrifugal wood is primary xylem. 8. In the foliar strands of the embryo and seedling, the xylem tissue, so far as developed, from below upward passes from an inner to a central position in reference to the whole bundle. 9. The girdle is established very early, and is horizontal from the beginning.