An anatomically preserved arborescent lycopsid, Sublepidodendron songziense (Sublepidodendraceae), from the Late Devonian of Hubei, China

Sublepidodendron is a common megafossil plant in the Late Devonian of China, but historically the generic delimitation based on leaf bases masked its true systematic position. A reinvestigation of S. songziense from the Late Devonian Hsiehchingssu Formation, Hubei, China, provides new insights into its internal anatomy and reproductive morphology. This arborescent lycopsid is characterized by small, vertically elongated leaf bases arranged in spirals, presence of false leaf scars, possibly bearing separate cones, and association with a stigmarian rhizomorph. The potential for organic connections of these detached organ genera has been noted for other Sublepidodendron species. The anatomy of S. songziense axes from two levels reveals that the thinner axis may bear an ectophloic siphonostele with a filamentous pith and an outer cortex. The thicker axis has a siphonostele with a branch gap, two-zoned pith with secondary thickenings, multiseriate rays across secondary xylem, a thick periderm, and primary and secondary tracheid walls characterized by "Williamson's striations." Similarities to synapomorphies of Diaphorodendraceae and Lepidodendraceae suggest that S. songziense bears a closer affinity to Lepidodendrales rather than Protolepidodendrales, as formerly thought. Widespread occurrence of Sublepidodendron implies that phylogenetically advanced arborescent lycopsids must have diverged by the Late Devonian.     

Sclerospiroxylon xinjiangensis nov. sp., a gymnospermous wood from the Kungurian (lower Permian) southern Bogda Mountains,northwestern China: Systematics and palaeoecology

A new silicified wood, Sclerospiroxylon xinjiangensis Wan, Yang et Wang nov. sp., is described from the Cisuralian (lower Permian) Hongyanchi Formation in southeast Tarlong section, Turpan City, Xinjiang Uygur Autonomous Region, northwestern China. The fossil wood is composed of pith, primary xylem and Prototaxoxylon-type secondary xylem. The pith is solid, circular, heterocellular, with sclerenchyma and parenchyma. The primary xylem is endarch to mesarch, with scalariform thickenings on tracheid walls. The secondary xylem is pycnoxylic, composed of tracheids and parenchymatous rays. Growth rings are distinct. Tracheids have mostly uniseriate, partially biseriate araucarian pitting on their radial walls. Helical thickenings are always present on both the radial and the tangential walls. Rays are 2–14 cells high, with smooth walls. There are 2 to 7, commonly 2 to 4 cupressoid pits in each cross-field. Leaf traces suggest that S. xinjiangensis nov. sp. was evergreen with a leaf retention time of at least 15 years. Based on the sedimentological evidence, growth rings within the S. xinjiangensis nov. sp. could have been caused by seasonal climatic variations, with unfavorable seasons of drought or low temperature. Low percentage of latewood in each growth ring is probably due to the intensity of climatic seasonality and/or long leaf longevity.     

Gymnosperm trees from the Permian of Antarctica: An anatomically preserved trunk of Kaokoxylon sp.

Anatomically preserved gymnosperm axes are relatively abundant in Permian localities of Antarctica, but their anatomy has rarely been studied in detail, which limits comparison with other Gondwanan morphotaxa. Here we describe a silicified trunk collected from the Upper Permian Buckley Formation at Coalsack Bluff, in the central Transantarctic Mountains. The trunk has a small heterogeneous pith approximately 4 mm in diameter containing conspicuous sclerotic nests, endarch primary xylem maturation, paired leaf traces, and secondary xylem of the Araucarioxylon type. Comparison with contemporaneous gymnosperm axes from Antarctica indicates that the Coalsack Bluff trunk represents a new Permian morphotaxon for the region. The anatomical characters of the pith and secondary xylem suggest an affinity with the genus Kaokoxylon Kräusel, previously reported from Permian and Triassic localities of Southern Africa, South America, India, and Australia.     

Deciphering the Niches of Colonisation of Vitis vinifera L. by the Esca-Associated Fungus Phaeoacremonium aleophilum Using a gfp Marked Strain and Cutting Systems

Introduction

Esca disease has become a major threat for viticulture. Phaeoacremonium aleophilum is considered a pioneer of the esca complex pathosystem, but its colonisation behaviour inside plants remains poorly investigated.

Material and Methods

In this study, P. aleophilum::gfp7 colonisation was assessed six and twelve weeks post-inoculation in two different types of tissues: in the node and the internode of one year-old rooted cuttings of Cabernet Sauvignon. These processes of colonisation were compared with the colonisation by the wild-type strain using a non-specific lectin probe Alexa Fluor 488-WGA.

Results

Data showed that six weeks post-inoculation of the internode, the fungus had colonised the inoculation point, the bark and xylem fibres. Bark, pith and xylem fibres were strongly colonised by the fungus twelve weeks post-inoculation and it can progress up to 8 mm from the point of inoculation using pith, bark and fibres. P. aleophilum was additionally detected in the lumen of xylem vessels in which tyloses blocked its progression. Different plant responses in specific tissues were additionally visualised. Inoculation of nodes led to restricted colonisation of P. aleophilum and this colonisation was associated with a plant response six weeks post-inoculation. The fungus was however detected in xylem vessels, bark and inside the pith twelve weeks post-inoculation.

Conclusions

These results demonstrate that P. aleophilum colonisation can vary according to the type of tissues and the type of spread using pith, bark and fibres. Woody tissues can respond to the injury and to the presence of this fungus, and xylem fibres play a key role in the early colonisation of the internode by P. aleophilum before the fungus can colonise xylem vessels.     

拐枣果序梗的发育解剖学研究

拐枣肉质膨大果序梗的发育过程可划分为前、中、后、末４个时期,前期为初生生长时期,内部结构类似一般双子叶植物茎的初生构造;中期为维管形成层活动时期,产生了不同其茎的次生木质部,由成片木质化的厚壁纤维细胞、一定量的木射线及星散在其中极少数的导管组成;后期为异常分生组织活动时期,初生木质部木薄壁组织及邻近少量髓细胞及邻近少量髓细胞转化为异常分生组织,向外产生切向排列的薄壁细胞,经扩大的切向伸长,使原导管     

白鲜根的发育解剖学研究

应用半薄切片、常规石蜡切片并结合离析法,对药用植物白鲜(Dictamnus dasycarpus Turcz.)根的发生发育过程进行了研究。结果表明:白鲜根的发生发育过程包括4个阶段,即原分生组织阶段、初生分生组织阶段、初生结构阶段以及次生结构阶段。原分生组织位于根冠内侧及初生分生组织之间,衍生细胞分化为初生分生组织。初生分生组织由原表皮、基本分生组织以及中柱原组成。原表皮分化为表皮,基本分生组织分化为皮层,中柱原分化为维管柱,共同组成根的初生结构;在初生结构中,部分表皮细胞外壁向外延伸形成根毛,皮层中分布有油细胞,内皮层有凯氏带,初生木质部为二原型或偶见三原型,外始式;根初生结构有髓或无。次生结构来源于原形成层起源的维管形成层的活动以及中柱鞘起源的木栓形成层的活动;白鲜次生韧皮部宽广,其中多年生根中可占根横切面积的85%,另外除基本组成分子外,还分布有油细胞;周皮发达,木栓层厚;初生皮层、次生木质部和次生韧皮部薄壁细胞中常充满丰富的淀粉粒。     

濒危植物海南风吹楠营养器官解剖结构特征

该研究采用石蜡切片和光学显微技术,对海南风吹楠营养器官的解剖结构及其对环境的适应性进行了探讨。结果表明:海南风吹楠为典型异面叶,叶片中脉发达,中部分化出髓,上表皮外侧具角质层,内侧具1层内皮层,下表皮外侧无角质层,有气孔器分布,气孔器为双环型,略下陷;栅栏组织3~4层细胞,海绵组织4~6层细胞。茎的初生结构中表皮轻微角质化,维管束为外韧型,8~10个初生维管束围绕髓排列为1轮;茎的次生结构中,表皮外部角质层加厚,维管柱紧密排列连成环状,次生韧皮部和次生木质部发达,形成层细胞3~5层。根的初生结构中表皮细胞外壁加厚,外皮层细胞体积大,形状不规则,内侧具1层形成层,内皮层具凯氏带,初生木质部为多原型,呈辐射状排列。根的次生结构中木栓层细胞5~6层,木栓层内侧具1层木栓形成层,栓内层细胞3层。海南风吹楠营养器官具有一定耐阴和耐旱结构特征,同时与其生活的热带雨林沟谷中高温荫湿的环境相适应。     

DISTRIBUTION AND RELATIONSHIP OF CELL DIVISION AND MATURATION EVENTS IN PISUM SATIVUM (FABACEAE) SEEDLING ROOTS

Pea roots have open apical organization, where discrete initial cells do not exist. Differentiation of all tissues occurs in cylinders and vascular sectors that blend gradually with each other. This study reports the distribution of dividing cells and their relationship to maturation events in the 2 mm root tip, and in the 8–10 and 18–20 mm segments. Up to 200 μm from the root body/cap junction, cell division is uniformly distributed throughout all meristem regions. By 350 to 500 μ, xylem tracheary elements and cells of the pith parenchyma and middle cortex have stopped dividing. At this level cell division is almost entirely restricted to two cylinders, one composed of the inner root cap, the epidermis, and the outer cortex (outer cortex cylinder) and another composed of cells of the inner cortex, the pericycle and vascular tissue (inner cortex cylinder). When the protophloem matures, all cells in the phloem sector of the inner cortex cylinder, including the 1 layered pericycle, the endodermis and the phloem parenchyma, stop dividing. The 3–4 layered pericycle in the xylem sectors continues dividing until about 10 mm from the body/cap junction following the maturation of the protoxylem tracheary elements.     

The primary vascular system of Callixylon

The primary vascular system of Callixylon (main stem axes of Archaeopteris) is composed of a discontinous cylinder of longitudinal bundles from some of which traces diverge radially in a regular, helical pattern. Tangential divisions and fusions of primary xylem strands occur in approximately equal frequency and, thus, the number of bundles in the system remains constant in the specimen studied. Following divergence, traces increase in size and become ribbed distally. The available evidence suggests that all of the traces observed in this study are branch traces. Branch bases, embedded in secondary xylem, have the anatomical characteristics of penultimate axes of lateral branch systems of Archaeopteris. It is suggested that some regions of main axes of Archaeopteris might have borne lateral branch systems only, lacking entirely simple leaves. Lateral branch systems, therefore, might have been more similar to compound leaves than previously supposed.     

The anatomy of the hypocotyls of Ceriops Arnott (Rhizophoraceae), Recent and fossil

Fragments of the hypocotyls of the fossil Ceriops cantiensis Chandler from the Lower Tertiary of southern England and the living Ceriops tagal (Perr.) C.B. Rob. and Ceriops decandra (Griff.) Ding How have been examined by SEM. The living material has also been studied by light microscopy. Great similarity has been revealed between homologous tissues of the Recent and fossil material: the palisade-like epidermis; a two-zoned cortex composed of an outer region of compact collenchymatous tissue and an inner region of aerenchyma; phloem fibres; a large number of small vascular bundles, only some of which have xylem; few xylem elements; similarity of xylem elements; pith region of roundish to shortly oblong cells forming long, bead-like rows in longitudinal view. Evidence is also presented of similarity between Recent and fossil starch grains.     

双穗雀稗(Paspalum distichum)通透性生理和茎解剖结构补充研究

双穗雀稗根外皮层,茎角质层和茎节中的质外体屏障结构阻挡黄连素示踪液透过植物体。茎中机械组织包括周缘厚壁机械组织层,厚壁组织层和维管系统,髓部和皮层的蜂窝状厚角组织。茎中通气组织包括茎节间髓部和皮层的蜂窝状通气组织,茎节内的通气组织。双穗雀稗茎节间具有外侧、内侧和维管系统的质外体屏障,以及茎节周围质外体屏障的封闭结构。因此,该植物体完善的机械组织、通气组织、质外体屏障结构及其离子不通透性是其适应湿地环境的重要结构。     

ACTINOXYLON BANKSII GEN. ET SP. NOV.: A PROGYMNOSPERM FROM THE MIDDLE DEVONIAN OF NEW YORK

A new genus from a Middle Devonian locality near Cairo, N. Y., is described. Actinoxylon gen. nov. is based upon pyritic petrifactions. Three orders of branching are present: penultimate branch, ultimate branch, and leaf. The penultimate branch bears spirally arranged ultimate branches and leaves, the leaves apparently replacing the branches in the spiral. The ultimate branches bear opposite to subopposite and decussate leaves. The leaves are non-planated, unwebbed structures which show at least three dichotomies. Each segment of the leaf is terete as are all other axes. Internally the penultimate branch has a six-lobed actinostele with mesarch protoxylem areas, one or two per lobe. Secondary xylem is visible in the oldest parts of several specimens. The xylem has helical-reticulate, reticulate, scalariform and circular-pitted elements. The presumptive areas of phloem are occupied by cells with dark contents. The cortex is composed of a parenchymatous inner region and a sclerenchymatous outer region. The ultimate branch traces are at first three-lobed protosteles, later becoming four-lobed. Several ultimate branch traces also possess secondary xylem while within the cortex of the penultimate branch. The leaf traces are terete strands. Below each forking of a leaf segment there is a corresponding forking of the vascular strand. Actinoxylon is compared with the progymnosperms Actinopodium, Svalbardia, Archaeopteris, Siderella, and Tetraxylopteris. The anatomy of the penultimate branch of Actinoxylon is similar to that of Actinopodium, Archaeopteris macilenta, and Siderella. The ultimate branch traces of Archaeopteris and Actinoxylon are similar. The ultimate branch stele and pattern of trace formation in Actinoxylon is similar to the stelar configuration and trace formation in the r + 2 axes of Tetraxylopteris schmidtii. The unwebbed leaves are similar to those of Archaeopteris fissilis, Svalbardia, and the terminal units of the Aneurophytales.     

Cortical Bundles in the Persistent, Photosynthetic Stems of Cacti

We examined 62 species in 45 genera of the cactus subfamilyCactoideae; all had collateral cortical bundles that permeatedthe broad, water-storing inner cortex and extended to the baseof the outer, photosynthetic palisade cortex. Mean distancebetween cortical bundles was 0.75 mm, similar to the mean spacing(0.74 mm) of veins in leaves of Pereskia, a genus of relictleaf-bearing cacti. In 16 species, both young and extremelyold stem cortex was available for study: in all of these, olderbundles had larger amounts of phloem than did younger bundles,indicating that phloem had been produced for many years. Inten species, older bundles also had more xylem than youngerbundles. In two genera (Rhipsalis and Selenicereus) there werecaps of primary phloem fibres, and in a single species (Pilosocereusmortensenii) cortical bundle xylem contained libriform fibres.All cortical bundle tracheary elements were narrow (radius range,0.91–8.2 µm; mode, 1.8–2.7 µm), similarto Pereskia leaf vein elements (radius range, 1.8–2.7µm); this was much narrower than stem wood vessels (radiusrange, 10–42 um; mode, 23–28 µm). Longitudinalconduction of water and nutrients probably occurs predominantlyin stem wood, with cortical bundles maintaining the broad, voluminouscortex, the outer part of which is the plant's photosynthetictissue and the inner part of which stores water and starch.The cortex of the Cactordeae contains numerous leaflike characters;homeotic genes may be involved in its morphogenesis. Cactaceae, cortical bundles, homeotic, xylem, phloem, evolution     

THE DEVELOPMENTAL ANATOMY OF OPUNTIA BASILARIS. I. EMBRYO,ROOT, AND TRANSITION ZONE

The large seeds of Opuntia basilaris Engelm. & Bigel. show an unusually high percentage of germination, followed by a rapid development of the seedling during the first 30 days of growth. The primary root has six xylem arms alternating with six phloem poles around a large central pith. Development of metaxylem opposite each of the primary phloem poles results in the formation of eight collateral bundles. Secondary and tertiary roots have four xylem and phloem poles with xylem developing to the center of the stele. The transition zone is characterized by a gradual disappearance of all but two of the primary xylem arms of the root. Metaxylem development in the central portion of the transition zone interconnects the protoxylem poles forming a primary xylem cylinder around the central pith. The collateral bundles pass through the transition zone essentially without change.     

STRUCTURALLY PRESERVED FOSSIL PLANTS FROM ANTARCTICA. I. ANTARCTICYCAS,GEN. NOV., A TRIASSIC CYCAD STEM FROM THE BEARDMORE GLACIER AREA

Silicified stems with typical cycadalean anatomy are described from specimens collected from the Fremouw Formation (Triassic) in the Transantarctic Mountains of Antarctica. Axes are slender with a large parenchymatous pith and cortex separated by a narrow ring of vascular tissue. Mucilage canals are present in both pith and cortex. Vascular tissue consists of endarch primary xylem, a narrow band of secondary xylem tracheids, cambial zone, and region of secondary phloem. Vascular bundles contain uni- to triseriate rays with larger rays up to 2 mm wide separating the individual bundles. Pitting on primary xylem elements ranges from helical to scalariform; secondary xylem tracheids exhibit alternate circular bordered pits. Traces, often accompanied by a mucilage canal, extend out through the large rays into the cortex where some assume a girdling configuration. A zone of periderm is present at the periphery of the stem. Large and small roots are attached to the stem and are conspicuous in the surrounding matrix. The anatomy of the Antarctic cycad is compared with that of other fossil and extant cycadalean stems.     

Two new fossil matoniaceous stem genera from Tasmania, Australia

Two new genera, Tasmanopteris and Heweria, from Tasmania are the first definite permineralized rhizomes assignable to the Matoniaceae. Tasmanopteris richmondii sp. nov., of mide-Mesozoic age, is from the Lune River site in southwestern Tasmania and is composed of four or more annular solenostelos separated by cortices with an inner mesarch xylem ring and outer exarch xylem rings. Secretory canals occur in the cortices between the protoxylem clusters of its outer xylem rings. The specimen of Heweria kempii sp. nov., which is very similar to extant Matonia, was collected from a Lower Tertiary conglomerate in central Tasmania but was reworked from older sediments. Anatomically, the rhizomes of Heweria consist of 3–6 annular solenosteles with the inner and middle xylem rings being mesarch, whereas the outer ring is exarch. Roots arise opposite the protoxylem clusters of the outermost ring. Epidermal hairs on the stems of this genus are like those of living Matonia in being attenuate, uniseriate, and multicellular.

Associated venation pattern of partially preserved leaves, isolated sporangia, annuli, and spores in this specimen provide additional support for the relationships of this fossil to modern Matonia.     

Palaeosmunda Emended and Two New Species

The genus Palaeosmunda was established by R. E. Gould in 1970 based upon some Late Permian Osmundaceous trunks with well-developed leaf gaps and rhomboidal sclerotic ring within petiolar base seen in cross section. As he thinks that the latter character is more important than the former, this genus could not be assigned to any subfamily of Osmundaceae. However, the leaf gap is one of the most important characters in the structure of the fern stem, so the author suggests that this genus should be assigned to subfamily Osmundoideae and its diagnosis must be emended as follows: The genus Palaeosmunda is represented by some rhizomes (or trunks), roots and leaf bases of ferns which structurally are preserved, resembling Osmundacaulis but which can’t be assigned to any group of this genus. Stem containing an ectophloic dictyoxylic siphonostele; if tracheids present in the pith, they being multiseriate scalariform pitted; pith or cortex sometimes contain ing groups of secretory cells or sclerenchyma; number of leaf traces seen in a tran sverse section of cortex more than 30; leaf traces adaxially curvature, rarely oblong shaped; petiolar bases with or without stipular expansion, containing a C-shaped vascular strand; root diarch. Type species——Palaeosmunda williamsii. According to this diagnosis some primitive osmundaceous species with the leaf gaps, which have already found in Upper Permian and Lower Triassic, could be assigned to this genus. Two of them are P. williamsii Gould and P. playfordii Gould, and Osmundacaulis beardmorensis, which was from Lower Triassic of Antarctica in 1978, should be assigned to the genus Palaeosmunda. In this paper two osmundaceous new species: P. primitiva and P. plenasioides were found in the coal balls of Upper Permian age from Wangjiazhai of Shuicheng of Guizhou Province, China. P. primitiva is represented by two trunks; stem about 4 cm in diameter; stele actophloic dictyoxylic siphonostele; pith cavity about 3—4 mm in diameter, contianing parenchyma and tracheids; xylem cylinder thin, less than 10 tracheids in radial thickness, dissected by leaf gaps. Inner cortex about 1.5 cm thick, mainly parenchymatous, but sometimes containing a few sclerenchymatous; number of leaf traces seen in a transverse section about 50—60; leaf traces departing at 35—45º,open C-shaped at point of departure, gradually becoming shallow C-shaped or V-shaped in different parts; protoxylem in base of leaf traces single, endarch; when leaf traces pass through inner cortex, protoxylem biturcating. Petiole bases without stipular expansion, probablyloosely embracing the stem; xylem strand of potiole trace shallow C-shaped, surrounded by selerenchyma; sclerotic ring round, connected with single sclerenchyma mass in the concavity of the petiole trace. Root arising singly from leaf trace, diarch, with inner and outer cortex. P. plenasioides is represented by a rhizome; stem more than 4 cm in diameter; stele actophloic dictyoxylic siphonostele; xylem cylider with about 20 tracheids in radial thickness, dissected by leaf gaps; xylem bundle U-, O-, or crosier- (i.e. query-) shaped; pith and inner cortex parenchymatous, with many groups of secretory cells; leaf trace C-shaped, its base containing two endarch protoxylem groups; root diareh,with inner and outer cortex, arising singly from leaf trace or its base.     

Polyamine levels in buds and twigs of Tilia cordata from dormancy onset to bud break

The fluctuations of free and bound polyamines (PAs) were studied in vegetative buds and underlying twigs of linden (Tilia cordata L.) from August to May, to assess the connection between PA levels and seasonal cycles of growth and dormancy. Outer and inner bud scales and shoot tips (short shoot tips with leaf initials in contiguous short internodes) were analyzed separately, as were phloem with cortex and xylem with pith tissue from twigs. Seasonal variations in PA levels were present in buds and twigs during the research period. The most abundant PA in buds and twigs in free and bound forms was spermidine followed by putrescine. PA amounts were low in buds and twigs in autumn. In twig tissues, free PAs were predominant whereas in bud scales, bound PAs accumulated over free PAs in autumn, first in inner scales and later in outer scales as well. PA levels did not increase dramatically during the onset of dormancy in autumn but lower temperatures and probable cold hardening correlated positively with bound PAs in bud scales. In shoot tips with leaf initials, and contiguous short internodes, free putrescine and spermidine levels rose simultaneously with bud burst and new growth, while bound PAs diminished quite radically from temporary bud scales and from growing shoot tips.     

Distribution of Cd and Zn in annual xylem rings of young spruce trees [Picea abies (L.) Karst.] grown in contaminated soil

Concentrations and total amounts of Cd and Zn in individual annual xylem increments of 5-year-old spruce trees (Picea abies) were investigated after one growing season in contaminated soils. The plants had been potted in soils amended with different concentrations of Cd and Zn and kept in open air conditions. In the outer xylem rings formed during the treatment period lowest concentrations of Cd and Zn were found. In inner rings concentrations of both elements increased and were highest at the pith. Total amounts of both elements showed reversed distribution patterns with highest values in the outermost rings. The observed increase of total dry matter of the rings from pith towards the outer rings was stronger than the parallel increase in total element amounts in the rings. Thus, concentrations dropped in younger rings. The time of the soil contamination event cannot be inferred from element concentrations in annual rings. The results challenge the concept of monitoring historical trends in trace element pollution using analytical data of tree rings of conifers.     

STIGMARIAN PETRIFACTIONS FROM THE PENNSYLVANIAN OF COLORADO

The designation Stigmaria ficoides is restricted to casts and impressions. Petrifactions of Stigmaria arnoldii sp. n. occur in Pennsylvanian age strata in Trout Creek Pass, Colorado. The rootlet gaps of this species appear narrow and elongate in both cross and longitudinal sections. Rootlet traces are contiguous with the secondary xylem to its outer margin and are surrounded by a small parenchyma sheath in the middle cortex. The outer cortex consists of an inner layer of primary tissue and a relatively thick zone of periderm. S. arnoldii most closely resembles material described as S. ficoides from England. Various stigmarian characters are evaluated with regard to their systematic or ontogenetic significance.