Observations on the formation, development, and structure of the tuber of Testudinaria elephantipes, and on the origin of the vegetative shoot

1935 ◽  
Vol 49 (332) ◽  
pp. 593-610 ◽  
Author(s):  
E. N. Sparshott
Keyword(s):  
Vascular Tissue ◽  
Developmental Stages ◽  
Adventitious Shoots ◽  
Secondary Growth ◽  
Longitudinal Section ◽  
Growth Zone ◽  
Vegetative Shoot ◽  
Growth Rings ◽  
Growth Zones ◽  
Medullary Parenchyma

Summary The young plants used for these observations were grown from seed collected in the Southern Karroo. The tuber of Testudinaria elephantipes is at first small, white, and spherical. Later it turns brown and develops a flattened or concave base and a thin continuous periderm. In the older, massive, semi-globular condition the tuber has a thick, deeply fissured, corky crust. Towards the base of the tuber the cork forms a thinner layer, broken only by the protrusion of roots. Various developmental stages are figured. There is no cork over a small area at the apex of the tuber. The growing point of the vegetative shoot is in this region, and is enclosed within a number of persistent scale leaves. The seed contains a small embryo embedded in considerable endosperm. There is no suggestion of tuberisation in the embryo. The development of the seedling is described and figured. A longitudinal section suggests that the plumular axis consists at first of little more than a stem apex and one leaf. Lack of opportunity for translocation of food synthesised is probably the cause of tuberisation. An explanation of the lack of symmetry is suggested. Tuberisation is not due to fungal infection. The anatomy of seedlings at different stages of development is described. The initial thickening of the hypocotyl results partly from cell division and partly from hypertrophy of the cortical parenchyma cells. Tuberisation is finally due to secondary growth originating in the pericycle. The early development of the cork crust and the growth zone is described. The structure of a three-year old tuber is dealt with in some detail. In general, the growth zone is hemispherical. Beneath the apex and just above the base no continuous meristem appears, though local growth zones may be found over the base. Vascular strands and medullary parenchyma are cut off towards the inside of the meristem, and secondary parenchyma towards the outside. The vascular tissue forms a small flat network under the apex and a larger network over the base, and these plates are connected by a complex system of anastomosing vascular strands running down the side of the tuber towards the inside of the growth zone. These vascular systems form growth rings. The bulk of the tissue cut off from the growth zone is parenchymatous. Fissures abutting on the medullary rays appear in the cork. The exposed parenchyma within the cork becomes suberised and a new band of cork is formed. Over the base of the tuber the original cork layer persists. An explanation is given for the origin of adventitious shoots. The sympodial origin of the seasonal vegetative shoots formed at the apex of the tuber is described and figured. The tuber is held to consist of a secondarily thickened hypocotyl and a very short epicotyl.

scholarly journals Prunus necrotic ringspot virus Early Invasion and Its Effects on Apricot Pollen Grain Performance

2007 ◽  
Vol 97 (8) ◽  
pp. 892-899 ◽  
Author(s):  
Khalid Amari ◽  
Lorenzo Burgos ◽  
Vicente Pallas ◽  
María Amelia Sanchez-Pina
Keyword(s):  
Developmental Stages ◽  
Generative Cell ◽  
Pollen Grains ◽  
Growth Zone ◽  
Pollen Tubes ◽  
Climatic Conditions ◽  
Pollen Grain ◽  
Ringspot Virus ◽  
Prunus Necrotic Ringspot Virus

The route of infection and the pattern of distribution of Prunus necrotic ringspot virus (PNRSV) in apricot pollen were studied. PNRSV was detected both within and on the surface of infected pollen grains. The virus invaded pollen during its early developmental stages, being detected in pollen mother cells. It was distributed uniformly within the cytoplasm of uni- and bicellular pollen grains and infected the generative cell. In mature pollen grains, characterized by their triangular shape, the virus was located mainly at the apertures, suggesting that PNRSV distribution follows the same pattern as the cellular components required for pollen tube germination and cell wall tube synthesis. PNRSV also was localized inside pollen tubes, especially in the growth zone. In vitro experiments demonstrated that infection with PNRSV decreases the germination percentage of pollen grains by more than half and delays the growth of pollen tubes by ≈24 h. However, although PNRSV infection affected apricot pollen grain performance during germination, the presence of the virus did not completely prevent fertilization, because the infected apricot pollen tubes, once germinated, were able to reach the apricot embryo sacs, which, in the climatic conditions of southeastern Spain, mature later than in other climates. Thus, infected pollen still could play an important role in the vertical transmission of PNRSV in apricot.

Intra-Annual Spiral Compression Wood: A Record of Low-Frequency Gravitropic Circumnutational Movement in Trees

IAWA Journal ◽  
1988 ◽  
Vol 9 (3) ◽  
pp. 269-274 ◽  
Author(s):  
Frank W. Telewski
Keyword(s):  
Pinus Taeda ◽  
Woody Plants ◽  
Compression Wood ◽  
Secondary Growth ◽  
Low Frequency ◽  
Wood Formation ◽  
Growth Rings ◽  
Movement Data ◽  
Annual Growth Rings ◽  
Plant Seedlings

The majority of detailed studies on circumnutational growth movements have focused on herbaceous plants or on the primary growth of woody plant seedlings, ignoring completely secondary growth in woody plants. The relatively rapid movement in herbaceous tissues consists of two components: an autonomous growth rhythm and a gravitropic response. Since there is a gravitropic component to circumnutational movement and a gravitropic stimulus can induce compression wood formation, the formation of a compression wood spiral may be expected if there is a circumnutational movement of a woody stern. It is suggested here, that observed spirals of compression wood within annual growth rings in Pinus taeda L. and Abies concolor (Gord. ' Glend.) Lindl. ex Hildebr. represents an annual record of a slower circumnutational growth movement. Data derived from observations of greenhouse- grown 3-year-old Pinus taeda seedlings indicate that there are two distinct circumnutational patterns of different rotation al frequency present in woody plants associated with primary and secondary tissues.

Ontogeny of divided vascular cylinders in Serjania: the rise of a novel vascular architecture in Sapindaceae

IAWA Journal ◽  
2021 ◽  
pp. 1-13
Author(s):  
Yanã C. Rizzieri ◽  
Arno F.N. Brandes ◽  
Israel L. Cunha Neto ◽  
Genise V. Somner ◽  
Michaela J.N. Lima ◽  
...  
Keyword(s):  
Vascular Tissue ◽  
Developmental Stages ◽  
Vascular Cylinder ◽  
Peripheral Vascular ◽  
Micro Computed Tomography ◽  
Cambial Variant ◽  
Complex Forms ◽  
Cambial Cells ◽  
Developmental Analysis ◽  
Cambial Variants

Abstract Sapindaceae lianas are remarkable for the diversity of cambial variants found in their stems. One of the family’s exclusive cambial variant is the divided vascular cylinder, which occurs in eight species of the genus Serjania. This cambial variant is marked by 5 peripheral vascular cylinders around a large pith. We performed a comparative developmental analysis, integrating traditional plant anatomy techniques with high-resolution X-ray micro-computed tomography to investigate the structure and development of the stems of three species with divided vascular cylinder. Our observations showed that the initial stages of stem development were similar to those described in the literature, however, on later developmental stages a central vascular cylinder appears in all species. The ontogeny of these stems are marked by three main processes: (i) dissection of vascular tissue from the peripheral vascular cylinders; (ii) development of new cambial arcs through the redifferentiation of pith cells; and (iii) recruitment of cambial cells from the inner portions of the vascular cambium of the peripheral vascular cylinders, forming a novel central vascular cylinder where the pith was, surrounded by five initial peripheral cylinders. As an ulterior developmental stage, some older stems also develop neoformations and connections between the different vascular cylinders. While our findings support previous descriptions of divided vascular cylinders, this is the first study illustrating the formation of the central vascular cylinder in this cambial variant. Our observations further corroborate that Serjania is the lineage with the highest and some of the most complex forms of cambial variants among all vascular plants.

scholarly journals Development of successive cambia and wood structure in stem of Rivea hypocriteriformis (Convolvulaceae)

2016 ◽  
Vol 61 (1) ◽  
pp. 89-98 ◽  
Author(s):  
Kishore S. Rajput
Keyword(s):  
Secondary Xylem ◽  
Monsoon Season ◽  
Secondary Growth ◽  
Vascular Bundles ◽  
Growth Rings ◽  
Successive Cambia ◽  
Initial Stage ◽  
Ray Cells ◽  
Cell Layers ◽  
Ray Parenchyma Cells

Abstract This study examined the formation of successive rings of cambia in Rivea hypocriteriformis Choisy (Convolvulaceae). The mature stem is composed of four to five rings of xylem alternating with phloem. Successive cambia originate as smaller and larger segments; union and anastomosing of small cambial segments often leads to the formation of discontinuous rings. In the initial stage of growth, several vascular bundles interconnect to form the first ring of vascular cambium. The cambium remains functional for one complete season and becomes dormant during summer; a new ring of cambium is completed prior to the subsequent monsoon season and sprouting of new leaves. Successive cambia are initiated from the pericyclic parenchyma situated three to four cell layers outside of the protophloem. Functionally, all the successive cambia are bidirectional and produce secondary xylem centripetally and phloem centrifugally. The secondary xylem is diffuse-porous, with indistinct growth rings and consisting of wide fibriform vessels, fibre tracheids, and axial and ray parenchyma cells. The xylem rays are uni- to multiseriate and heterocellular. The multiseriate rays contain lignified marginal ray cells and thin-walled, unlignified central cells. The central ray cells also show accumulations of starch and druses. Discrete strands of intraxylary phloem occur at the periphery of the pith, and additional intraxylary phloem develops from adjacent cells as secondary growth progresses. Earlier-formed phloem shows heavy accumulation of callose, followed by its compaction. The development of successive cambia is correlated with extension growth and with the phenology of the plant.

scholarly journals X. On the organization of the fossil plants of the coal-measures. —Part IX

1878 ◽  
Vol 169 ◽  
pp. 319-364 ◽  
Keyword(s):  
Vascular Tissue ◽  
Transverse Section ◽  
Great Majority ◽  
Longitudinal Section ◽  
Variable Number ◽  
Transverse Diameter ◽  
Fossil Plants ◽  
Circular Orifice ◽  
Coal Measures ◽  
Medullary Cells

In Part I. of this series of memoirs (Phil. Trans. 1871, Plate 25, fig. 16, and Plate 27, fig. 39, p. 487) I described what appeared to be a transverse section of a Calamite, in which the woody wedges showed no traces of the longitudinal canal that occupies the innermost angle of each of these primary wedges in true Calamites. Not having at that time the materials which I have since accumulated, I was unable to say much about this exceptional specimen. I now know that it is not a Calamite, but a plant having a wholly different structure, and to which I propose assigning the provisional name of Astromyelon, from the peculiar stellate form which transverse sections of its pith exhibit. The plant had branching, unarticulated stems, a feature which at once distinguishes it from the Calamites, though transverse sections of the two plants exhibit such remarkable resemblances. It is one of the more common of the forms met with in the Oldham nodules. I have rarely seen specimens of it more than 0·25 in diameter. One example alone, represented in fig. 5, has had a diameter of nearly 0·75. Fig. 1 represents the more usual aspect of transverse sections of this plant enlarged 20 diameters. It consists of a central parenchymatous medulla, a , surrounded by an exogenous cylinder of vessels arranged in a very regular series of primary wedges, b , corresponding closely in all respects with those of Calamites, except in the absence of the long canals already referred to. The central cells of the medulla are much larger than those of the circumference, some of the former having a diameter of ·011, whilst the peripheral ones are not more than ·0041. In the longitudinal section, fig. 2, a , and fig. 3, a ', these medullary cells are seen to be somewhat elongated vertically, being often ·022 in length. The cells have usually rectangular partitions, and are arranged in vertical rows, as in many living ferns; one or two of the rows in immediate contact with the vascular zone (fig. 3, a ') have a similar arrangement, though they are much narrower in their transverse diameter. In the great majority of cases the pith is solid. In but a few instances have I found it otherwise. Two of the latter are represented in figs. 4 and 5. Fig. 5 further presents an example in which the medulla has had an unusually great diameter in proportion to that of the vascular zone. This exogenous zone is made up of a variable number of primary vascular wedges (figs. 1, b , 5, b ), each one of which is composed of numerous radiating vascular laminæ separated by medullary rays. The remarkable uniformity in their size and the regularity in the arrangement of these wedges gives to the transverse sections of the medulla the star-shaped outline already referred to. At their inner or medullary apex each of these wedges commences at a few vessels of somewhat larger size than those composing the rest of the vascular zone. These are observable in fig. 1, but they are much more conspicuous in some examples than in others. Fig. 7 represents a section, for which I am indebted to Mr. Butterworth, in which these vessels are extremely conspicuous. The medulla of this specimen is much disorganized by mineralization, but it has not been fistular. Its diameter is much less than is usually the case, contrasting strongly in this respect with fig. 5. In Mr. Binney’s monograph on the Calamites he figured, at page 20, what he believed to be part of a primary wedge of a Calamite, adding the remark, that in these Calamites “the wedge-shaped bundles of pseudo-vascular tissue originate from a small circular orifice or opening, sometimes simple, as in the specimen now under consideration, but in other instances apparently divided into several parts, as shown in the annexed woodcut (fig. 3).” I have no doubt that the latter examples were specimens of Astromyelon, which, like myself, Mr. Binney then mistook for Calamites.

scholarly journals Mental Resilience of Medical Practitioners in Singapore during COVID-19: Survey Results from a Webinar Course on Resilience

2021 ◽  
Vol 18 (18) ◽  
pp. 9801
Author(s):  
Cheng Hong Charity Low ◽  
Tze Jui Goh ◽  
Yiong Huak Chan ◽  
Daniel Shuen Sheng Fung ◽  
Pak Yean Cheong
Keyword(s):  
General Practitioners ◽  
Family Physicians ◽  
Growth Zone ◽  
Front Line ◽  
Effective Response ◽  
Medical Practitioners ◽  
Growth Zones ◽  
Survey Results ◽  
Risk Of Exposure ◽  
Mental Resilience

Front-line doctors are at high risk of exposure to COVID-19. The mental resilience of general practitioners and their areas of concerns and support required are important during this COVID-19 period. A total of 403 general practitioners attending a webinar on resiliency, hosted by the College of Family Physicians, Singapore, participated in the survey anonymously. Participants provided responses to questions relating to COVID-19 in the domains of Family and friends, Myself, Practice, and Community. Responses are categorized into LEARNING, FEAR, and GROWTH zones. The majority of the doctors reported to be in the GROWTH zone in relation to Family and friends (39%) and Myself (38%) as compared to Practice and Community, aOR = 4.5 (95% CI 3.4 to 5.9), p < 0.001. 34% of the participants reported being in the FEAR zone in relation to Family and friends, aOR = 8.0 (95% CI = 5.6 to 11.2), p < 0.001; at least 81% reported being in the LEARNING zone in relation to Practice and Community, aOR = 7.5 (95% CI = 5.8 to 9.6), p < 0.001, compared to other domains. Supporting and protecting the doctors is important in strategic planning and management of the current pandemic and building preparedness and an effective response towards future crises.

Inter-regional cluster formation based on the concept of spatial development

2020 ◽  
Vol 18 (4) ◽  
pp. 688-708
Author(s):  
L.I. Pronyaeva ◽  
A.V. Pavlova ◽  
O.A. Fedotenkova
Keyword(s):  
Economic Growth ◽  
Cluster Formation ◽  
Growth Zone ◽  
Inclusive Development ◽  
Expert Assessment ◽  
Regional Clusters ◽  
Regional Cluster ◽  
Growth Zones ◽  
Smart Specialization ◽  
Forming Methods

Subject. This article discusses the organizational and economic processes, and conditions for the formation and development of inter-regional clusters. Objectives. The article aims to clarify ideas and develop recommendations to assess the conditions and possibilities of inter-regional cluster forming. Methods. For the study, we used statistical analysis, graphical, and expert assessment methods, and a literature review. Results. The article proposes certain phases and an algorithm to form inter-regional clusters as potential economic growth zones of the regions. Conclusions and Relevance. The inter-regional cluster formation and development should be based on the economic-growth-zone theory and models based on the principles of inclusive development and smart specialization. The results of the study may be a basis to develop a strategy for inter-regional clusters operating at the level of the country's macro-regions.

Floral ontogeny and anatomy of the shrub Gaiadendron punctatum and a comparison of floral characters in the tribes Gaiadendrinae and Nuytsiae (Loranthaceae)

2021 ◽  
Vol 69 (3) ◽  
Author(s):  
Hernán Darío Suárez ◽  
Camila Robayo ◽  
Xavier Marquínez ◽  
Lauren Raz
Keyword(s):  
Vascular Tissue ◽  
Developmental Stages ◽  
Floral Anatomy ◽  
Phylogenetic Analyses ◽  
Molecular Data ◽  
Inflorescence Development ◽  
Mountainous Regions ◽  
Phylogenetic Studies ◽  
Molecular Phylogenetic ◽  
Floral Characters

Introducction: Gaiadendron punctatum is a hemiparasitic species of Loranthaceae (Tribe Gaiadendreae) that is widely distributed in mountainous regions of Central and South America. Embryological and phylogenetic studies in the family indicate a trend towards reduction of the gynoecium and ovules, the morphology of which supports the current circumscription of Tribe Gaiadendreae (Gaiadendron and Atkinsonia). Molecular phylogenetic studies suggest that Nuytsia, Atkinsonia and Gaiadendron diverged successively, forming a grade at the base of the Loranthaceae, but support values are low. Objetive: In the present study, the floral anatomy of Gaiadendron punctatum was investigated in order to provide additional data to permit comparisons among the three basal-most genera in the Loranthaceae and reevaluate their relationships. Methods: Flowers of G. punctatum were collected at different developmental stages and serial sections were prepared and analyzed by light microscopy. Results: Inflorescence development is acropetal; the flowers are bisexual with an inferior ovary surmounted by a calyculus, a ring-shaped structure lacking vascular tissue; the ovary is comprised of seven basal locules, each with an ategmic, tenuinucellate ovule. Above the locules is a mamelon that is fused with the adjacent tissues. The androecium is comprised of seven epipetalous stamens, the anthers with fibrous endothecium dehiscence through a single longitudinal slit, releasing tricolpated pollen. Conclusions: The results of this study show that Gaiadendron and Atkinsonia share versatile, dorsifixed anthers, while Gaiadendron and Nuytsia share the same mode of anther dehiscence. On the other hand, Gaiadendron shares with members of Tribe Elytrantheae an amyliferous mamelon and an unvascularized calyculus. Combined phylogenetic analyses of morphological and molecular data are desirable to determine whether Tribe Gaiadendreae comprises a clade, a grade or if the two genera are more distantly related.

Dorsal-fin spine growth of Heterodontus portusjacksoni: a general model that applies to dorsal-fin spines of chondrichthyans?

2008 ◽  
Vol 65 (1) ◽  
pp. 74-82 ◽  
Author(s):  
Javier Tovar-Ávila ◽  
Christopher Izzo ◽  
Terence I Walker ◽  
J Matias Braccini ◽  
Robert W Day
Keyword(s):  
Growth Zone ◽  
Layer Growth ◽  
Spine Length ◽  
External Edge ◽  
Dorsal Fin ◽  
Growth Increments ◽  
Second Growth ◽  
Growth Bands ◽  
Growth Zones ◽  
Prospective Model

A prospective model of dorsal-fin spine growth in chondrichthyans is devised by studying the growth of spines from captive and wild Heterodontus portusjacksoni injected with several fluorochromes. Evidence was found for only two dentine layers in the spine trunk of H. portusjacksoni, contrasting with conjectures about the presence of a third middle dentine layer in some squalids. The spines have three simultaneous growth zones. The first growth zone is along the internal edge of the inner trunk dentine layer, where growth bands are deposited towards the centre (centripetally), increasing spine length and width by pressure against the cartilage rod. The second growth zone is along the external edge of the outer trunk dentine layer at the spine base, where growth bands are deposited in an opposite direction to the centre (centrifugally), increasing spine width. A third growth zone at the base of the cap enables downward expansion over the trunk. The model of concentric cones describes correctly the inner dentine layer growth pattern, whereas the outer dentine layer growth increments appear to be related to the external bands on the surface of the trunk. Growth increments from the three growth zones of the spine are all potentially useful for age estimation.

Refined bomb radiocarbon dating of two iconic fishes of the Great Barrier Reef

2015 ◽  
Vol 66 (4) ◽  
pp. 305 ◽  
Author(s):  
Allen H. Andrews ◽  
John H. Choat ◽  
Richard J. Hamilton ◽  
Edward E. DeMartini
Keyword(s):  
Great Barrier Reef ◽  
Radiocarbon Dating ◽  
Growth Zone ◽  
Barrier Reef ◽  
Hermatypic Coral ◽  
Advanced Technologies ◽  
Bomb Radiocarbon ◽  
Growth Zones ◽  
Bolbometopon Muricatum ◽  
Age Estimates

Refinements to the methodology of bomb radiocarbon dating made it possible to validate age estimates of the humphead wrasse (Cheilinus undulatus) and bumphead parrotfish (Bolbometopon muricatum). Age for these species has been estimated from presumed annual growth zones in otoliths at ~30 and ~40 years respectively. The validity of these estimates was tested using bomb radiocarbon dating on the small and fragile otoliths of these species, and provided an opportunity to refine the method using advanced technologies. A regional Δ14C reference record from hermatypic coral cores from the Great Barrier Reef was assembled and Δ14C measurements from extracted otolith cores of adult otoliths were successful. Validated ages supported the accuracy of growth zone derived ages using sectioned sagittal otoliths.

Sign in / Sign up

Export Citation Format

Share Document