Meristematic Layer Research Articles

塊茎分割によるシクラメンの栄養繁殖 (第2報)

In the previous paper of 1979, the author reported that cyclamen could be vegetatively propagated by means of notching on the cut surface after the upper part of the planted tuber was scooped.In the present paper, the suitable site of tuber scooping and size of tuber notching for the vegetative propagation are examined. And the initial points of the adventitious buds developed on the scooping surface of the tuber and its margin, and of the adventitious bud occurring on the epidermis of the tuber are further observed from an anatomical viewpoint.The results are as follows:1. The site of scooping and the size of notching.It seems to be suitable for this propagation that the tuber was scooped at one third of the upper part and the cut surface notched into one centimeter squares.2. The point of initiation of adventitious bud primordia.In the case of adventitious buds growing from the scooping surface, the original body of the bud occurred in the vascular cut end and its periphery. On the other hand, in the case of adventitious buds growing from the margin of the scooping surface, the original body occurred in the meristematic layer, where old periderm and new wound-periderm joined together. And moreover, in the case of adventitious buds growing from the epidermis, the leaf primordia of the bud originated from the neighborhood of the cork cambium in the periderm.

Morphological and SDS-polyacrylamide Gel Electrophoretic Studies of Pro-embryoid Formation in the Petiole Explants of Chinese Celery

The sequence of development leading to the formation of pro-embryoids in the petiole explants of Chinese celery was followed anatomically and by using SDS-gel electrophoresis of soluble proteins at 0, 2, 4, 6, 8 and 10 days of culture. Three distinctive developmental stages were recognized, viz. 0-4, 4-10 and 10 or more days of culture. At 0–4 days of culture, no apparent structural changes took place. At 4-10 days of culture, cortical cells situated near the vascular bundles towards the cut ends of the explant began to proliferate and form layers of meristematic cells with very dense cytoplasm. At 10 or more days of culture, the meristematic layers of cells encircling the vascular bundles began to give rise to numerous pro-embryoids. The stages of formation of pro-embryoids observed anatomically appeared to be associated closely with changes in the types of soluble protein formed in the explants as revealed by the electrophoretograms.

Fine Structure of Established Callus Cultures of Taraxacum officinale Weber

The nodular, brown callus cultures of Taraxacum officinale grow slowly on a modified White's medium. A section of nodule reveals a meristematic layer bounded both internally and externally by parenchymatous tissue. No other types of tissue occur within the callus. The cells of the inner parenchyma are often compressed and senescing, whereas in the outer tissue localized de-differentiation apparently contributes to the development of new nodules during callus growth. Fine-structural observations of both meristematic and parenchymatous tissues show the normal complement of higher plant cell organelles except for the apparent absence of cytoplasmic microtubules. The rough endoplasmic reticulum cisternae are often aligned parallel to the cell wall or in whorls and may show pores, thus resembling annulate lamellae. Numerous lipid bodies, up to 7 μm wide, occur and these are sometimes invested by arrays of apparently membranous material. The mitochondria are frequently highly branched and often show a scalariform arrangement of cristae. The plastids show few internal membranes despite culture of the callus under continuous illumination. Lomasomes are very common in all cells and in the parenchyma tissue membranous wall bodies also occur. The latter bodies are much larger than lomasomes and consist of wall overgrowths in which vesicular, myelin-like or isolated membranous elements are enmeshed in fibrillar material. It is suggested that membranous wall bodies may originate from the amalgamation and subsequent proliferation of several adjacent lomasomes.

An Interchange Mosaic inAloe BarbadensisMill.

SUMMARYAn interchange mosaic in a clone of Aloe barbadensis Mill, is reported. The interchange has taken place between the two long non-homologous chromosomes, the L1 and the L4. It is unequal and appears only in a few flower buds and root tips. The interchange probably occurred in the meristematic layer during the formation of a new sucker affecting both the root and the shoot system.

SPORANGIAL STRUCTURE AND ZOOSPOROGENESIS IN CHORDA TOMENTOSA (LAMINARIALES)1,2,3

SUMMARYMembers of the genus Chorda represent the simplest form of sporophyte in the order Laminariales. The present study deals with reproduction in Chorda tomentosa, involving the initiation, growth, and structure of the sporangium and the process of zoosporogenesis. The simple tube‐like sporophyte of Chorda tomentosa grows in diameter by means of repeated anticlinal divisions in a superficial meristematic layer known as the meristoderm. The onset of reproduction is marked by the conversion of the meristoderm from contributing cells to the vegetative plant body to producing 2 new cell types: paraphyses and sporangial mother cells. At the time of initiation, sporangial mother cells are crescent shaped and possess a densely staining cytoplasm. Sporangial mother cells increase in size, become ellipsoid, decrease in staining density, and undergo meiosis. After meiosis, sporangia increase in size while their nuclei undergo successive cycles of synchronous mitotic divisions. Sporangia increase to a maximum length of 120 μ;m at which time they possess the characteristic “cap” found in all members of the order studied thus far. At this stage the protoplast of the sporangium is organized into a peripheral layer of nucleus‐chloroplast pairs and a central region of vacuoles. Cleavage furrows begin to form at the cell membrane and are met by furrows developing in the interior of the cytoplasm resulting in the division of the entire protoplast into separate units. Each unit is an individual zoospore. The biflagellate zoospores contain a nucleus, one chloroplast with eyespot, perinuclear Golgi, and several bodies of presumed storage carbohydrate. The occurrence of a small population of early developing sporangia is described. In essential details, the origin, development, and structure of sporangia in Chorda tomentosa are identical to all earlier observations in the Laminariales.

Morphological Studies in the Roots of Zingiberaceae

A study of the histogenesis at the root apex in Costus speciosus, Hedychium coronarium, Curcuma angustifolia, C longa and Zingiber officinale has shown two types of root apex configuration. In the first four species, three distinct initial layers, one each for the plerome, periblemprotoderm complex and the calyptrogen were observed, whereas, in Zingiber officinale only one initial layer responsible for the development of all the histogens of the root body has been recorded. Cellular differentiation in the subapical region of the root proceeds differently in the two cylinders; the plerome and the periblem. The plerome cylinder has a meristematic activity chiefly confined to the peripheral layers; the periblem cylinder, on the other hand, shows meristematic activity in both, the peripheral and the inner layers. Protoderm is early differentiated from the periblem-protoderm complex. Cortical tissues are chiefly contributed by the innner meristematic layer of the periblem, but some of it is also derived from the outer meristematic layer. The inner most layer of the outer meristematic zone finally matures into the endodermis. Hence, the differentiation of the tissue in the periblem is both centripetal and centrifugal. The plerome cylinder develops by a peripheral meristematic zone only. The differentiation is, therefore, only centripetal. The outermost layer of the meristematic zone matures into the pericycle, which retains its meristematic character throughout. While studying the vascular differentiation in the root, it was observed that the metaxylem cells are the first to become conspicuous by the rapidly widening cells with enlarged vacuoles. These are followed by the first protoxylem cells and then by the first phloem elements. Thus the cellular differentiation is in order-metaxylem-protoxylem-phloem; but the maturation of the elements proceeds in an order: protoxylem-metaxylem-phloem.

DEVELOPMENTAL STUDIES ON EUPHORBIA ESULA L.: APICES OF LONG AND SHORT ROOTS

In both indeterminate long roots and determinate short roots of Euphorbia esula L., the promeristem usually consists of three meristematic layers. One of these represents the stelar pole, the second is continuous with the cortex, and the most distal appears to initiate the root cap – epidermis complex. Variations in this pattern are noted. Autoradiographs of apices of roots supplied with thymidine-H3 under field conditions demonstrate the existence of a region of low nuclear incorporation during a 24 or 48 hour period at the summit of the root axis in long roots. This region corresponds to the quiescent center described by previous authors. Short root apices consistently lack such a region. The pattern of nuclear incorporation of thymidine-H3 suggests that cell division is infrequent or absent in the center of the apex of long roots but not of short roots. Quiescence is thus a phenomenon which is superimposed upon the organization of the root apex in this species, and its presence or absence seems to be related to the developmental potentiality of the root. In many long roots the size of this quiescent region exceeds that of the region which may reasonably be designated the promeristem.

Modes of union and interaction between parasite and host in the Loranthaceae. VII. Some Australian Loranthoideae with exceptional features

Specimens received from Australia during 1961 and 1962 included types of attachment additional to those described in part VI (Thoday 1961). In particular Diplatia maideni from the Northern Territory, on species of Acacia , had formed longitudinally running haustorial strands in the outer phloem of the host. From these parallel strands, slender branches penetrated radially, with further ramifications, reaching the host cambium in many places and forming ‘sinkers’ grafted into the wood. On some hosts the parasite had formed strands upwards as well as downwards. Another species of Diplatia , D. grandibractea , had formed on Eucalyptus microtheca a large attachment bearing a group of shoots. The parasite extended downwards as a haustorial strand longitudinally against the host wood. Between the dark surface tissues of the parasite and the smooth pale bark of the Eucalyptus was a zone marked by transverse fissures and ridges where host and parasite tissues were interlocked, the parasite having formed marginal tongues growing out actively into the host, with some response on the part of the host. In the strands of D. maideni , groups of stone cells and xylem are differentiated and the prominent xylem strands increase radially by an external meristematic layer. Parenchy­matous rays are formed in the process and in them stone-cell masses are differentiated, supplementing the larger masses formed in the rest of the strands. These strands together form a tangential zone in the outer part of the host, which with the xylem becomes increasingly prominent, so that the surface becomes ribbed and in parts fissured by the resulting tension. Some additional examples of longitudinal strands against the host wood were also included among the specimens, as well as of tangential flange formation. Specimens of Amyema sp. increased the range of attachment structure in that genus. A. pendula had longitudinal strands against the host wood. A. gibberula in particular was noteworthy as comparable with Diplatia maideni , but with coarser strands in Grevillea striata . Longitudinal strands against the wood were also found in A. congener on Alphitonia excelsa , Acacia cunninghamii , Acacia fasciculifera , Casuarina littoralis and Geijera parviflora , but not on Acacia melanoxylon or Flindersia australis ; also, less regularly, in A. lucasii on Flindersia sp. and sometimes in A. quandang , on Acacia harpophylla and Acacia kempeana . Other specimens of A. pendula had formed them on Eucalyptus melliodora , E. propulnea , hemiphloia and haemastoma , but not on E. Stuartiana or Acacia dealbata .

Istogenesi e caratteri anatomici dei tessuti ricavati da frammenti di germoglio diSolanum TuberosumL. coltivatiIn Vitro

Abstract HISTOGENESIS AND ANATOMICAL CHARACTERISTICS OF PORTIONS OF SOLANUM TUBEROSUM SPROUTS CULTIVATED IN VITRO. — Disks cut from sprouts of Solanum tuberosum L. have been cultured on White's basic or modified medium (White, 1943) with 20 mg/l KH22PO4 50 mg/l adenine, and 12 or 24 mg/l NAA. Sections were prepared according to Morel's method (1948). Only on the disks cultured on White's modified medium with 12 mg/1/NAA growth glomerules and a normal meristematic layer were present, while there were no signs of cellular hypertrophy and organogenetic phenomena. 12 mg/l appears therefore to be the optimal dose of NAA for cultures of excised portions of potato sprouts. Adenine is however always necessary because it triplicates the growth activity of the tissues and because through its antagonism with regard to auxin it favours the genesis of the callus.

Modes of union and interaction between parasite and host in the Loranthaceae - V. Some South African Loranthoideae

Haustorial structure and behaviour are described for three South African species: Loranthus elegans ( Moquinia rubra ), L .( Tapinanthus ) prunifolius and L . ( Taxillus ) glaucus . Fundamental differences are revealed between them, although they are nearly related. In Moquinia rubra the haustorium extends against the wood and maintains contact by a meristematic surface layer with large parts of the host cambium, which continues to function, but forms only phloem where in contact with the haustorial meristem. In Tapinanthus prunifolius the haustorium spreads against the wrood, but interrupts the cambium and links up with the phloem ; numerous xylem connexions are established between radial surfaces of host wood and parasite. In both these species variations are described, attributable to relative age and vigour of host and parasite, or, in Moquinia rubra , to a different host. In Taxillus glaucus the haustorium does not penetrate to the cambium but spreads and branches in the outer tissues below the periderm, and then sends m any fine sinkers radially to the wood, where they become embedded like coarse medullary rays, including xylem elements. This aberrant form is closely matched by an unrelated American species, Psittacanthus sternbergianus , described by Solms-Laubach. Reference is made to still another type of attachment, the ‘wood-rose’ type, already described for a South African species, L . ( Erianthemum ) dregei , and a similar specimen is illustrated.

Fossil Cryptogams

THE exogenous(circumferential)growth of fossil vascular cryptogams is a subject of so much interest and importance, that I may perhaps be permitted to say a few words regarding it. In a paper which was read at the December meeting of the Edinburgh Botanical Society, I combated the idea of the circumferential growth of calamites. The moist nature of the soil in which calamites must have grown would lead one to expect a poor development of the fibro-vascular bundles, and in comparing what I believe to be the fibro-vascular bundles of calamites with those of our recent equisetums, this idea is fully confirmed. Then in Equisetum there is a large development of the sclerenchyma of Mettenius, which forms the strong hypoderma. In a Brazilian fern which has come under my notice, this sclerenchyma runs to the fibro-vascular bundles, and presents an appearance exactly like Williamson's woody wedges, the large and small cells giving an appearance wonderfully like medullary rays. There is another point which, to my mind, is of much importance; namely, that in most of our recent vascular cryptograms, the embryonic parts do not enlarge; but as each successive leaf and portion of stem is produced, every such leaf and portion of stem is larger than the part preceding it, and this continues until a certain maximum is reached, when the stem becomes cylindrical. It is impossible to overlook that this mode of growth is evident in calamites, and until convincing proof can be brought forward of the circumferential growth of calamites, I must decline to accept it. Turning from the calamites to Lepidodendron, it is evident that in it circumferential growth was much more likely to have occurred. In the calamites there is no evidence that they required year by year increasing quantities of water for purposes of transpiration, while in Lepidodendron the numerous small leaves which must have gone on increasing in number during the whole life of the plant (which however need not have been very long) demands that some addition to the conducting tissue should be made. As in botany we constantly find the same physiological purpose provided for in many morphologically distinct ways, I do not think it is at all necessary to believe in a form of growth identical with that in dicotyledons, because that would involve a complete change in type. Looking at such a stem as Lycopodium chamaecyparissus, in which the cortical tissues become so curiously modified, there is no difficulty in imagining that an increase by means of a cortical meristem might take place, a condition which I believe still exists in Isoetes. Hegelmaier in his paper. “Zur Morphologie der Gattung Lycopodium” in the Botanische Zeitung, 1872, p. 796, points out the presence in lycopods of a peculiar layer which he calls the phloem sheath, outside the phloem of the bundle, but inside the cortical portion, and therefore a series of cells belonging to the plerom and not to the periblem tissues. It seems to me probable that this phloem sheath may have represented a meristem layer from which new tissue was formed, as it would be the representative of the plerom meristem of the higher plants, while its position outside the vessels would further seem in some way related to the absence of vessels in the secondary wood of conifers.

Notes on Hanstein’s Researches on the Development of the Embryo in Monocotyledons and Dicotyledons (Die Entwicklung des Keimes der Monokotylen und Dikotylen, von Dr. Johannes Hanstein, ‘Botanische Abhandlungen, Heft 1)

ABSTRACT In Cryptogams the tissues at the growing-point of a stem or root always form by division from a single apical cell. Hanstein, in his researches on the development of the tissues at the growing-point of the stem of Phanerogams, found that the tissues were developed, not from a single apical cell, as in Cryptogams, but from a tissue of similar cells. In only two cases did he trace back the development to the embryo in the seed. The question, therefore, still remained to be answered as to when the separation of the different meristem layers took place in the embryo, and whether the cells formed from a tissue or a single apical cell.

Exogenous Structure in Coal-Plants

THE points at issue between Prof. Williamson and myself remain in the same position as at first. He has not yet answered one of my objections. He still holds that in Lepidodendron we have a vascular medulla, outside which is a series of fibrovascular bundles which are not closed, but go on forming new tissues by means of a cambium layer like a dicotyledonous stem. From my own observations, and from the study of recent Continental authorities, I have no hesitation in stating that the central “medulla” of Prof. Williamson consists of the united closed, fibro-vascular bundles, while the investing cylinder is the modified primitive tissue which increases in diameter by means of the meristem layer of Nageli. If Prof. Williamson will refer to Sachs' Lehrbuch, Ed. 2, p. 397, he will find good reasons given for the statement there made that Isoetes contains no cambium in the stem; but that the stem increases in the same way as Dracaena, i.e. by a meristem layer in the primitive tissue. As long as Prof. Williamson believes in a central vascular medulla in these Lycopodiaceous stems, all his other conclusions must likewise be false.