The cell biology of wood formation: from cambial divisions to mature secondary xylemThis review is one of a selection of papers published in the Special Issue on Plant Cell Biology.

2006 ◽  
Vol 84 (4) ◽  
pp. 631-639 ◽  
Author(s):  
A.L. Samuels ◽  
M. Kaneda ◽  
K.H. Rensing
Keyword(s):  
Cell Biology ◽  
Secondary Xylem ◽  
Vascular System ◽  
Structural Information ◽  
Cell Structure ◽  
Wood Formation ◽  
Point Of View ◽  
Anatomical Point ◽  
Recent Developments ◽  
Gene Expression Studies

The development of secondary xylem has been studied historically from an anatomical point of view, but recent developments in cell and molecular biology have revitalized this field. An integrated view of cell structure with physiology is emerging for each stage of the developing xylem cells’ lives, from birth in the cambium to programmed cell death. High-quality structural information is essential in building this type of integrated view, but conventional electron microscopy of developing wood cells has been problematic. The importance of adequately preserving cells of the secondary vascular system is illustrated with examples from dormant cambium, cell division, and secondary cell wall deposition. In many cases, contemporary gene expression studies can be viewed in the context of both new structural information and pioneering live cell studies done in the early 1900s to increase our understanding of secondary xylem development.

scholarly journals Learning from the past – the origin of wood

2008 ◽  
Vol 84 (4) ◽  
pp. 498-503 ◽  
Author(s):  
Rodney Arthur Savidge
Keyword(s):  
Cell Biology ◽  
Secondary Xylem ◽  
Secondary Growth ◽  
Wood Formation ◽  
Late Triassic ◽  
Primary Xylem ◽  
Tree Ferns ◽  
Severe Climate Change ◽  
Middle Carboniferous ◽  
Extinction Events

Trees were on Earth 394 million years ago (394 Ma) as spore-producing Archaeopteris progymnosperms having largediameter trunks of secondary xylem (morphotype Callixyon) produced by vascular cambium. Plants of smaller stature with primary xylem cores were present in Late Silurian (416 Ma), but they lacked cambium and it remains unclear how and when the first trees evolved. Progymnosperms faded and gymnosperms arose during Middle Carboniferous, and conifers, ginkgos, cycads, tree ferns and cordaites were well established by the Carboniferous–Permian transition (299 Ma). Woods of the earliest conifers were different from those of today, and not until Late Triassic (220 Ma) did any begin producing secondary xylem similar to modern woods, the xylem phenotypes of Cupressaceae and Araucariaceae emerging much earlier than those of Pinaceae and flowering plants. Conifers have persisted and done relatively well despite major extinction events, severe climate change, insectivory, herbivory and microbial activity, all of which were in effect before as well as during the appearance of trees on Earth. Approximately 600 conifer species continue to exist, and the survivors presumably possess the physiological fitness needed to adapt to an ever-changing biosphere. However, this is speculative because their physiology remains less than well understood. Forestry interventions such as planting one species to the exclusion of others have the potential to exacerbate as well as sustain the ongoing existence of our remaining conifers. Key words: bordered pit, cambium, cell biology, cellulose, evolution, lignin, paleobotany, protoplasmic autolysis, secondary growth, wood formation, xylogenesis

scholarly journals Leaf anatomy and histochemistry of Macropeplus dentatus (Perkins) I. Santos & Peixoto and Macropeplus ligustrinus (Tul.) Perkins (Monimiaceae)

2010 ◽  
Vol 24 (3) ◽  
pp. 852-861 ◽  
Author(s):  
Fernanda Flores Costa ◽  
Helena Regina Pinto Lima ◽  
Maura Da Cunha ◽  
Inês da Silva Santos
Keyword(s):  
Phenolic Compounds ◽  
National Park ◽  
Vascular System ◽  
Neotropical Region ◽  
Anatomical Structure ◽  
Point Of View ◽  
Southeastern Brazil ◽  
Secretory Cells ◽  
Natural Park ◽  
Anatomical Point

The Monimiaceae is represented in the Neotropical region by six genera. Macropeplus Perkins is a Brazilian genus comprising four species restricted to high-montane Atlantic Forest areas, which have not been properly examined from the anatomical point of view. This study characterizes the anatomical structure and histochemical aspects of the leaves of Macropeplus dentatus and M. ligustrinus, and adds to our taxonomic knowledge ofthe genus. The individuals studied were collected in the Serra dos Órgãos National Park and in the Caraça Natural Park in southeastern Brazil. Among the characteristics common to the two species, hypostomatic leaves, dorsiventral structure, paracytic stomata, a subepidermal layer, collateral vascular system in the form of an arc in the petiole, semicraspedobrochidodromous venation, and the presence of prismatic crystals were registered. Intracellular metabolites, such as phenolic compounds, lipids and mucilage, were identified. The petiole shape, occurrence and distribution of secretory cells and brachysclereids, in association with other morphological features, were relevant to species identification.

scholarly journals Lipidomics study of plasma from patients suggest that ALS and PLS are part of a continuum of motor neuron disorders

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Estela Area-Gomez ◽  
D. Larrea ◽  
T. Yun ◽  
Y. Xu ◽  
J. Hupf ◽  
...  
Keyword(s):  
Motor Neuron ◽  
Motor Neurons ◽  
Cell Structure ◽  
Disease Onset ◽  
Point Of View ◽  
Motor Dysfunction ◽  
Cellular Processes ◽  
Progressive Muscle Weakness ◽  
Human Pathology ◽  
Lateral Sclerosis

AbstractMotor neuron disorders (MND) include a group of pathologies that affect upper and/or lower motor neurons. Among them, amyotrophic lateral sclerosis (ALS) is characterized by progressive muscle weakness, with fatal outcomes only in a few years after diagnosis. On the other hand, primary lateral sclerosis (PLS), a more benign form of MND that only affects upper motor neurons, results in life-long progressive motor dysfunction. Although the outcomes are quite different, ALS and PLS present with similar symptoms at disease onset, to the degree that both disorders could be considered part of a continuum. These similarities and the lack of reliable biomarkers often result in delays in accurate diagnosis and/or treatment. In the nervous system, lipids exert a wide variety of functions, including roles in cell structure, synaptic transmission, and multiple metabolic processes. Thus, the study of the absolute and relative concentrations of a subset of lipids in human pathology can shed light into these cellular processes and unravel alterations in one or more pathways. In here, we report the lipid composition of longitudinal plasma samples from ALS and PLS patients initially, and after 2 years following enrollment in a clinical study. Our analysis revealed common aspects of these pathologies suggesting that, from the lipidomics point of view, PLS and ALS behave as part of a continuum of motor neuron disorders.

scholarly journals Verbena officinalis Verbenaceae (Lamiales): a new plant model system for phyllotaxis research

2021 ◽  
Author(s):  
Beata Zagórska-Marek ◽  
Magdalena Turzańska ◽  
Klaudia Chmiel
Keyword(s):  
Vascular System ◽  
Cumulative Effect ◽  
Point Of View ◽  
Theoretical Point ◽  
Inflorescence Axis ◽  
Organ Identity ◽  
Lateral Organ ◽  
Complex Relationships ◽  
Secondary Transitions

AbstractPhyllotactic diversity and developmental transitions between phyllotactic patterns are not fully understood. The plants studied so far, such as Magnolia, Torreya or Abies, are not suitable for experimental work, and the most popular model plant, Arabidopsis thaliana, does not show sufficient phyllotactic variability. It has been found that in common verbena (Verbena officinalis L.), a perennial, cosmopolitan plant, phyllotaxis differs not only between growth phases in primary transitions but also along the indeterminate inflorescence axis in a series of multiple secondary transitions. The latter are no longer associated with the change in lateral organ identity, and the sequence of phyllotactic patterns is puzzling from a theoretical point of view. Data from the experiments in silico, confronted with empirical observations, suggest that secondary transitions might be triggered by the cumulative effect of fluctuations in the continuously decreasing bract primordia size. The most important finding is that the changes in the primary vascular system, associated with phyllotactic transitions, precede those taking place at the apical meristem. This raises the question of the role of the vascular system in determining primordia initiation sites, and possibly challenges the autonomy of the apex. The results of this study highlight the complex relationships between various systems that have to coordinate their growth and differentiation in the developing plant shoot. Common verbena emerges from this research as a plant that may become a new model suitable for further studies on the causes of phyllotactic transitions.

scholarly journals Functional Characterisation of the Poplar Atypical Aspartic Protease Gene PtAP66 in Wood Secondary Cell Wall Deposition

Forests ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 1002
Author(s):  
Shenquan Cao ◽  
Cong Wang ◽  
Huanhuan Ji ◽  
Mengjie Guo ◽  
Jiyao Cheng ◽  
...  
Keyword(s):  
Cell Wall ◽  
Secondary Cell Wall ◽  
Fluorescent Protein ◽  
Secondary Xylem ◽  
Populus Trichocarpa ◽  
Wood Formation ◽  
Protease Gene ◽  
Cellulose Content ◽  
Transcription Analysis ◽  
Functional Characterisation

Secondary cell wall (SCW) deposition is an important process during wood formation. Although aspartic proteases (APs) have been reported to have regulatory roles in herbaceous plants, the involvement of atypical APs in SCW deposition in trees has not been reported. In this study, we characterised the Populus trichocarpa atypical AP gene PtAP66, which is involved in wood SCW deposition. Transcriptome data from the AspWood resource showed that in the secondary xylem of P. trichocarpa, PtAP66 transcripts increased from the vascular cambium to the xylem cell expansion region and maintained high levels in the SCW formation region. Fluorescent signals from transgenic Arabidopsis plant roots and transiently transformed P. trichocarpa leaf protoplasts strongly suggested that the PtAP66-fused fluorescent protein (PtAP66-GFP or PtAP66-YFP) localised in the plasma membrane. Compared with the wild-type plants, the Cas9/gRNA-induced PtAP66 mutants exhibited reduced SCW thickness of secondary xylem fibres, as suggested by the scanning electron microscopy (SEM) data. In addition, wood composition assays revealed that the cellulose content in the mutants decreased by 4.90–5.57%. Transcription analysis further showed that a loss of PtAP66 downregulated the expression of several SCW synthesis-related genes, including cellulose and hemicellulose synthesis enzyme-encoding genes. Altogether, these findings indicate that atypical PtAP66 plays an important role in SCW deposition during wood formation.

Characterization of Tilt Boundaries by Ultra High Resolution Electron Microscopy

1984 ◽  
Vol 41 ◽  
Author(s):  
W. Krakow ◽  
J. T. Wetzel ◽  
D. A. Smith ◽  
G. Trafas
Keyword(s):  
High Resolution ◽  
Grain Boundary ◽  
Structural Information ◽  
Theoretical Work ◽  
High Resolution Electron Microscopy ◽  
Point Of View ◽  
Experimental Point ◽  
Structure Information ◽  
Resolution Electron ◽  
Tilt Boundaries

AbstractA high resolution electron microscope study of grain boundary structures in Au thin films has been undertaken from both a theoretical and experimental point of view. The criteria necessary to interpret images of tilt boundaries at the atomic level, which include electron optical and specimen effects, have been considered for both 200kV and the newer 400kV medium voltage microscopes. So far, the theoretical work has concentrated on two different [001] tilt bounda-ries where a resolution of 2.03Å is required to visualize bulk lattice structures on either side of the interface. Both a high angle boundary, (210) σ=5, and a low angle boundary, (910) σ=41, have been considered. Computational results using multislice dynamical diffraction and image simulations of relaxed bounda-ries viewed edge-on and with small amounts of beam and/or specimen inclina-tion have been obtained. It will be shown that some structural information concerning grain boundary dislocations can be observed at 200kV. However, many difficulties occur in the exact identification of the interface structure viewed experimentally for both [001] and [011] boundaries since the resolution required is near the performance limit of a 200kV microscope. The simulated results at 400kV indicate a considerable improvement will be realized in obtain-ing atomic structure information at the interface.

Fuel Cells vs. Competing Technologies

2003 ◽  
Author(s):  
Supramanian Srinivasan ◽  
Lakshmi Krishnan ◽  
Andrew B. Bocarsly ◽  
Kan-Lin Hsueh ◽  
Chiou-Chu Lai ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Proton Exchange Membrane ◽  
Direct Methanol Fuel Cells ◽  
Cell Structure ◽  
Proton Exchange ◽  
Point Of View ◽  
Direct Methanol ◽  
Energy Conversion Systems ◽  
Competing Technologies

Investments of over $1 B have been made for Fuel Cell R&D over the past five decades, for space and terrestrial applications; the latter includes military, residential power and heating, transportation and remote and portable power. The types of fuel cells investigated for these applications are PEMFCs (proton exchange membrane fuel cells), AFCs (alkaline fuel cells), DMFCs (direct methanol fuel cells), PAFCs (phosphoric acid fuel cells), MCFCs (molten carbon fuel cells), SOFCs (solid oxide fuel cells). Cell structure, operating principles, and characteristics of each type of fuel cell is briefly compared. The performances of fuel cells vs. competing technologies are analyzed. The key issues are which of these energy conversion systems are technologically advanced and economically favorable and can meet the lifetime, reliability and safety requirements. This paper reviews fuel cells vs. competing technologies in each application category from a scientific and engineering point of view.

scholarly journals GRIBOV PROBLEM FOR GAUGE THEORIES: A PEDAGOGICAL INTRODUCTION

2004 ◽  
Vol 01 (04) ◽  
pp. 423-441 ◽  
Author(s):  
GIAMPIERO ESPOSITO ◽  
DIEGO N. PELLICCIA ◽  
FRANCESCO ZACCARIA
Keyword(s):  
Cross Sections ◽  
Gauge Theories ◽  
Functional Integral ◽  
Point Of View ◽  
Spherically Symmetric ◽  
Abelian Gauge ◽  
Gauge Transformations ◽  
Recent Developments ◽  
Gribov Ambiguity ◽  
Gribov Copies

The functional-integral quantization of non-Abelian gauge theories is affected by the Gribov problem at non-perturbative level: the requirement of preserving the supplementary conditions under gauge transformations leads to a nonlinear differential equation, and the various solutions of such a nonlinear equation represent different gauge configurations known as Gribov copies. Their occurrence (lack of global cross-sections from the point of view of differential geometry) is called Gribov ambiguity, and is here presented within the framework of a global approach to quantum field theory. We first give a simple (standard) example for the SU(2) group and spherically symmetric potentials, then we discuss this phenomenon in general relativity, and recent developments, including lattice calculations.

Concepts of Disease: A Textbook of Human Pathology, edited by Joel C. Brunson, M.D. and Edward A. Gall, M.D. New York/London/Toronto: The Macmillan Company, 1971, 1134 pp., $23.95

PEDIATRICS ◽  
1972 ◽  
Vol 49 (3) ◽  
pp. 484-484
Author(s):  
Gordon W. Vawter
Keyword(s):  
New York ◽  
Cell Biology ◽  
Organ Systems ◽  
Human Pathology ◽  
Recent Developments ◽  
Concepts Of Disease ◽  
Novel Design

This is a lusty 7½ pound newborn book with most organ systems more than adequately mature to assure a long and fruitful life. The two senior obstetricians enlisted the aid and advice of 36 other especially knowledgeable specialists to assure successful delivery. Concepts of Disease is a textbook of pathology with a novel design, emphasizing pathology as process, and incorporates much of the newer information derived from cell biology, and from the recent developments in ultrastructural and immunofluorescent techniques.

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