Central Vascular Bundle Research Articles

The Control of Food Mobilisation in Seeds of Cucumis sativus L. IV. The Pattern of Protein Degradation

Substantial protein degradation in the cotyledons of intact cucumber seedlings is initiated in the region of the primary (central) vascular bundle. Hydrolysis in the region of the secondary vascular bundles proceeds at a slower rate. Protein is subsequently hydrolysed in the mesophyll cells between the vascular bundles in a wave of activity moving from the abaxial to abaxial surface. The palisade cells are the last to lose their storage protein. A similar pattern of degradation occurs in cotyledons excised from the embryonic axis, although the rate of degradation is slower in this treatment. Starch accumulates in excised cotyledons, particularly in the vicinity of the vascular tissues. Starch is not detectable in the cotyledons of intact seedlings.

Host–parasite relationships and development of the ergot sclerotium in Claviceps purpurea

Conidia of Claviceps purpurea germinate on the stigmas of Secale cereale, and intercellular hyphae grow downward through the style and inner wall of the ovary to the tip of the rachilla. Across the tip of the rachilla, hyphae surrounding living host cells form a narrow interface that plunges downward into the central vascular bundle approximately to the level of origin of the lodicules. This biotrophic relationship is well established 5–6 days after infection at anthesis and persists unaltered through maturation of the ergot sclerotium at approximately the 28th day. Tissues in the base of the ovary above this interface are destroyed and replaced by fungus stroma. Xylem vessels in the tip of the rachilla are destroyed and replaced by a hyphal core extending downward from the stromatic foot of the fungus. Hyphae emerging between the epidermal cells of the ovary form an external matrix that contributes to further expansion of the stroma. A palisade of phialidic conidiophores develops over the surface of the stroma, which is involuted into labyrinthine chambers. Conidia ooze from the florets in drops of honeydew by the 6th or 7th day. The ovarian cap and the upper part of the ovule are pushed upward on the apex of the conidial stroma, and some of these isolated host cells remain alive until the 11th day. A layer of vertically arranged parallel hyphae across the base of the conidial stroma forms a generative zone that sharply delimits the basal stromatic foot seated in the floret and by apically directed intercalary growth produces the compact tissues of the ergot sclerotium. The sclerotium begins to protrude from the floret by the 11th day. The withered remnants of the conidial stroma and the ovarian cap are carried upward on the tip of the massive sclerotium. Beneath the dark rind the hyaline tissue of the sclerotium consists primarily of compacted, isodiametric storage cells. A loose hyphal conducting tissue forms a central strand from which narrow vanes radiate irregularly toward the periphery. Ergot of rye is a replacement disease in which the parasite disintegrates host tissues in areas required for development of its own structures while maintaining a compatible relationship with adjacent host cells as a source of water and nutrients.

Structure of nitrogen-fixing nodules formed by Rhizobium on roots of Parasponia andersonii Planch.

The structure of nitrogen-fixing nodules produced by Rhizobium infection of the non-legume Parasponia andersonii was examined by light and electron (both SEM and TEM) microscopy. Comparisons were made with the nodules previously described on P. rugosa. Like the nodules on different non-legumes formed by other types of endophytes, the Rhizobium nodules on Parasponia resembled modified roots by having a central vascular bundle surrounded by an endophyte-infected zone. The intimate association between the Rhizobium and the host nodule cell was compared with the Rhizobium association found in legumes. The rhizobia were not released from the infection thread as happens in the legume. The infection thread, which propagates the Rhizobium infection to new cells, was transformed within a nodule cell from a darkly stained (light microscopy) or very electron-dense (TEM) structure to a number of thread types. The walls of the threads varied greatly in thickness and often the thread structures were without rigid walls and were only enclosed by a plasma membrane. If the rhizobia are transformed into bacteroids, as in the legumes, it would have to occur when the threads had reached their mature size, when bacterial division had ceased. Nitrogen fixation was considered to occur in all thread types.

Virus‐like particles in phloem tissue of chervil (Anthriscus cerefolium) infected with anthriscus yellows virus

SUMMARYClusters of isometric virus‐like particles c. 22 nm in diameter, embedded in amorphous electron‐dense material, were found in the phloem tissue of Anthriscus cerefolium (chervil) plants infected with the semi‐persistent aphid‐borne virus, anthriscus yellows (AYV). The particles resembled those seen previously in thin sections of AYV‐transmitting aphids (Cavariella aegopodii). The particles were found only in the central vascular bundle of the petiole and its continuation in the leaf midrib. They were also found in extracts made by grinding petiole and midrib tissue in 10 % sucrose using Carborundum. These results confirm earlier studies which suggest that AYV is confined to deeper‐lying tissues.

Microfilaments and microtubules in elongating parenchyma cells of Nymphoides indica

Observations on microfilaments and microtubules in elongating parenchyma cells of the central vascular bundle of Nymphoides indica (L.) O. Kuntze petiole are reported and discussed in relation to current concepts of the involvement of cellular organelles in cell wall synthesis.

Leaf blade and midrib anatomy of two sugarcane cultivars of Bangladesh

Context: Kranz anatomy of locally developed sugarcane cultivars were studied in relation to C4 vascular arrangement. Objective: The objective of this study was to make gross cross-sectional anatomy and quantitative assessment of the anatomic traits of the leaf-blade and midrib of the sugarcane cultivars. Materials and Methods: Leaf blade and leaf sheath of two sugarcane cultivars Ishurdi 20 and Ishurdi 32 were used as the materials. Free hand section with appropriate stain were used. Sections were studied using an advanced biological system microscope fitted with motic camera. Anatomic traits were studied through motic image plus J 1.0 software using Macintosh computer. Results: Three sized vascular bundles and significant differences in distance between those vascular bundles were noted. Ishurdi 32 possessed two sized vascular bundles. Large vascular bundles characters by two large metaxylem vessels on either side of protoxylem. Phloem well developed. Intermediate and small bundles lack metaxylem vessels and protoxylem, but have metaphloem with thick and thin walled sieve tubes. Bundle sheaths have extended to upper and lower epidermis but for small bundle it is extended to abaxial epidermis. Vascular bundles are almost completely surrounded by chlorenchymatous bundle sheath and associated with hypodermal sclerenchyma on both abaxially and adaxially except small blade bundles which associated with the abaxial sclerenchyma. Bundle sheath cells were smaller in large and larger in other two types of vascular bundle. An inner mestome sheath with thickened walls is always present round the phloem and metaxylem around all or part of the xylem in large and intermediate bundles. In small bundles mestome sheath is altogether absent. Bulliform cells with varied area were present on the adaxial epidermis opposite to small vascular bundles. Midrib anatomy consists of central large vascular bundles lacking bundle sheath cells pushed deep inside parenchymatous hypodermis from abaxial hypodermal sclerenchyma girders. Lack of Kranz traits, and bundle sheath cells have transformed into sclerenchymatous bundle cover. Central mid-rib large bundle flanked by 3-10 small bundles on either side of midrib which have Kranz system of anatomy. Midrib region have continuous hypodermis consists of sclerenchyma cells and it is few layer (Ishurdi 32) to multilayer (Ishurdi 20). Conclusion: Kranz system with well developed bundle sheath associated with Kranz mesophil in the leaf blade were observed but Kranz tissue absent in midrib region. Large and small vascular bundles alternate all alone the leaf blade. Bulliform cell well develop indicates zeric adaptation. Two cultivars differ in respect of quantitative expression of Kranz tissue. Keywords: Sugarcane cultivar; Kranz tissue; bulliform cells; mestome sheath. DOI: http://dx.doi.org/10.3329/jbs.v18i0.8778 JBS 2010; 18(0): 66-73

Developmental Aspects of the Shoot Apex, Leaf, and Beltian Bodies of Acacia cornigera

The final event of leaf ontogeny in Acacia cornigera is the production of a Beltian body at the tip of each rachis and pinnule. This structure serves as a food source for an ant, Pseudomyrmex ferruginea F. Smith, that lives in a mutualistic relationship with the plant. The mature Beltian body consists of an epidermis, hypodermis, cortex and central vascular bundle. Anatomical and cytohistological comparisons between the shoot apex and leaf ontogeny in A. cornigera and similar developmental aspects of the phyllode of A. longifolia Willd. and of the leaf of A. decurrens var. dealbata F.v.M. indicate that each type of photosynthetic organ is characterized by a different period of longevity of its group of sub-apical initials. The phylogenetic history of Beltian bodies is also discussed.

DEVELOPMENTAL ASPECTS OF THE SHOOT APEX, LEAF, AND BELTIAN BODIES OF ACACIA CORNIGERA

The final event of leaf ontogeny in Acacia cornigera is the production of a Beltian body at the tip of each rachis and pinnule. This structure serves as a food source for an ant, Pseudomyrmex ferruginea F. Smith, that lives in a mutualistic relationship with the plant. The mature Beltian body consists of an epidermis, hypodermis, cortex and central vascular bundle. Anatomical and cytohistological comparisons between the shoot apex and leaf ontogeny in A. cornigera and similar developmental aspects of the phyllode of A. longifolia Willd. and of the leaf of A. decurrens var. dealbata F.v.M. indicate that each type of photosynthetic organ is characterized by a different period of longevity of its group of sub‐apical initials. The phylogenetic history of Beltian bodies is also discussed.

Studies on the Development of Crown Roots in Rice-Seedlings

1.The author had observed the development of crown roots of seedlings by using five varieties of rice, which especially it centered at the 2nd-node and the 3rd-node. 2. In the cotyledonaly node, the origin of the crown root was formed from five places that faced each other to the phloem which existed to the outside of the vascular bundle. 3. When it was manages by the α-Nathtalen acetic acid, in the cotyledonary node the origin of six crown roots was formed in it, but it was increase of on origin in the fixed position which faced each other in the central vascular bundle on the side of the seminal root.

ON THE STRUCTURE OF THE CONE SCALES OF LEPIDOSTROBUS

IN a set of six serial sections primarily designed to exhibit the structure of a cone of Sphenophyllum Dawsoni occur a number of foliar organs having such thick-walled cells that these organs form a conspicuous feature of the slides. Further study has borne out the early opinion that these foliar organs present certain features of novelty, and may clear up some points regarding the lepidodendroid cone, so an account of them has seemed worth putting on record. These slides were prepared by Mr James Lomax, who has furnished the following data: Loc. Upper Foot Mine, Shore, Littleborough, Lancashire. The state of preservation of this material is for the most part admirable, even certain thin-walled cells of the vascular area being preserved in some of the sections. The light brown colour of the cell walls appears to indicate rapid penetration of the petrifying liquid. The general features are brought out in P1. III, figs. i and 2, which show the exceedingly simple shape of these objects. They are almost flat, although some sections indicate a slight concavo-convex shape, i.e. the scales were very slightly trough-shaped. No projecting midrib or lateral grooves have been found, but the organs were thickest at the middle, tapering gradually right and left to a very thin margin. Measurements of the thickness of nineteen scales were made at the region of the single central vascular bundle. The thinnest scale measured o045 mm. and the thickest o go mm., with an average of o-67 mm. Sections extending from midregion to edge of a scale were scarce, but seven half-scales were measured, the minimum width being 9-I8 mm., the maximum 205 mm., and average I3-07 mm., all being calculated for width of a whole scale. The length of a slightly slanting longitudinal section (broken off at each end) was 32 mm. The similarity of the various transverse sections indicates that the scales were lanceolate, and the dimensions clearly show that they were not acicular. The plan of the scale as seen in transverse section (P1. III, fig. 2) shows a single central bundle, and at a short distance right and left

Helophyton Williamsonis

AT the late York meeting of the British Association two of my indefatigable auxiliaries in the work of Carboniferous investigation, Mr. Wm. Cash, F.G.S., of Halifax, and Mr. Thomas Hick, M.A., B.Sc., of Harrogate, described, under the name of Hymenophylloides Williamsonis, a new stem of a plant, which they had obtained from the Halifax beds. This plant is an extremely interesting one, since its cortical layer exhibits the large, open, longitudinal lacunæ, formed by dissociation, so common amongst aquatic plants. It is still more interesting since the septa separating the large lacunæ are rotate, each one consisting of a single layer of cells, and the whole combining to constitute a network with vertically elongated meshes. This arrangement approaches too closely to that seen in the living Marsileaceæ, to be overlooked in considering the possible affinities which it may indicate. The structure of the central vascular bundle as well as of its component vessels differs decidedly from that of the recent Marsileæ and their allies. But it differs still more widely from Myriophyllum, with which the generic name given to it by my two friends associates it. This circumstance alone makes it important to change the name. As yet we have found no trace of an angiospermous phanerogam in the Carboniferous beds, and any name suggesting the probability of the existence, of such is apt to be misleading. But apart from this suggestion of improbable affinities a second reason exists for changing the name. Urrger has already adopted that of Myriophyllites for a genus of Tertiary plants, and the two names approach too nearly to make it desirable that both should be retained. One point appears to be indisputable:— The structure of the bark already referred to indicates either a marsh or an aquatic plant—an interesting fact, since it is the first example of such a plant from the palæozoic rocks that has hitherto come under my notice. We have numerous so-called aquatic roots described by various authors—and possibly they may be what they are affirmed to be, though we have no proof that such is the case; but I think that no such doubts can exist in reference to our new plant. Under these circumstances I propose for this plant the generic name of Helophyton, a name which involves no foregone conclusions as to its botanical affinities. Detailed figures of it will appear in the next (12th) part of my memoirs “On the Organisation of the Plants of the Coal-measures.

III. Notice of further researches on the fossil plants of the coal-measures

My dear Dr. Sharpey,—Since I read my last communication to the Royal Society on the organization of the Fossil Plants of the Coal-measures I have done a large amount of work, having cut between two and three hundred new sections and with most satisfactory results. I have obtained a series of specimens almost completing the life-history of one plant from Burntisland, beginning with the tips of the smallest twigs and ending with the large stems. The former are mere aggregations of parenchyma with a central bundle of barred vessels mixed with a small amount of primitive cell-tissue. As the twig grew the leaves assumed definite form, and the central vascular bundle opened out at its central part, so as to form a cylinder, the interior of which was occupied by parenchyma. This cylinder grew rapidly, the number of its vessels steadily increasing; but they were all equally arranged as in, what I have termed, the medullary vascular cylinder, i. e. not in radiating series. We thus obtain the origin of that remarkable cylinder, and see that it is the expanded homologue of the central vascular bundles of the living Lycopods. Whilst these processes were in progress the cortical portion became differentiated into layers, and the parenchymatous cells of the pith continued to multiply, so as to occupy the expanding interior of the vascular cylinder. After attaining a certain size, through the above processes, a new element of growth appeared; an exogenous addition was made to the exterior of the cylinder, also consisting of barred vessels, but these are arranged in the radiating series described in my last memoir. This series continued to grow until it attained to considerable dimensions; but the entire vascular system always remains small, compared with the diameter of the stem, the chief bulk of which consists of an enormously thick bark. The structure just descibed is that of a true example of the genus Diploxylon of Corda. But I have got abundance of specimens with leaves on the exterior of the bark, demonstrating that the plant is a true Lomatophloios , thus indicating the correctness of my supposition, advanced in my last memoir, that sooner or later the genus Diploxylon would have to be abandoned.