The Uptake Properties of the Root System

2000 ◽  
Author(s):  
Peter B. Tinker ◽  
Peter Nye
Keyword(s):  
General Structure ◽  
Root Surface ◽  
Root Cap ◽  
Ion Uptake ◽  
Root Tip ◽  
Detailed Knowledge ◽  
Uptake Mechanism ◽  
Single Root ◽  
System P ◽  
The Subject

The uptake of nutrient and other ions into the root from the surrounding soil is the main topic of this book. To understand it, we need to know how the nutrient uptake and demand of the plant is expressed at the root surface. The main interest is on how the demand at the root surface can be quantitatively defined in terms of its uptake characteristics. For this reason, our explanation of the ion uptake mechanism of the root itself is brief, and is intended mainly for readers who have not studied the subject deeply. The subject has become considerably more complex since 1977, but this detailed knowledge has not yet coalesced into a full model of how ions are absorbed, such as ultimately will allow root uptake properties to be predicted. There have been many good reviews in the recent past, and the following may be consulted: Clarkson & Hanson 1980; Glass 1983; Luttge 1983; Clarkson 1985; Sanders 1990; Clarkson & Luttge 1991; Marschner 1995. We will describe the structure of a single root only briefly here, since this information can be found in standard texts (Troughton 1957; Esau 1965; Cutter 1978; Fahn 1982). Figures 5.1-5.5 show the general structure, but here we stress points that have a special bearing on the process of ion uptake or root behaviour in soil. Byrne (1974) noted that the anatomy of soil-grown roots may differ somewhat from that of solution-grown roots. The architecture of whole root systems in soil is dealt with in chapter 9.The root tip is a highly important part of the root. The apical meristem (the ‘quiescent centre’) is a fraction of a millimetre behind the visible root tip; cells that form behind the centre of this develop into the root, whereas those in front of the centre form the root cap. These cells gradually reach the surface of the cap, and there are rubbed off and lost into the soil at a rate of several thousand per day in maize. Often, these cells are visible in the mucigel that forms from the base of the root cap and covers the young root (section 8.1.3), and can remain alive in the gel for a period.

Clausewitz and the Eighteenth-Century Context of Partisan Warfare

2018 ◽  
Author(s):  
Sibylle Scheipers
Keyword(s):  
Eighteenth Century ◽  
Intellectual Development ◽  
Small Wars ◽  
System P ◽  
The Subject ◽  
Partisan Warfare

Clausewitz was an ardent analyst of partisan warfare. In 1810 and 1811, he lectured at the Berlin Kriegsschule, the war academy, on the subject of small wars. Clausewitz’s lectures focused on the tactical nature of small wars. However, the eighteenth-century context was by no means irrelevant for Clausewitz’s further intellectual development. On the contrary, he extrapolated from his analysis of the tactical nature of small wars their strategic potential, as well as their exemplary nature for the study of war as such. The partisan, in Clausewitz’s eyes, possessed exemplary qualities in that he acted autonomously and, in doing so, had to draw upon all his human faculties. As such, he was the paradigmatic antagonist to the regular soldier who displayed a ‘cog mentality’ fostered by the Frederickian military system.

Cytological and histochemical characteristics of the axenic root surface of Alnus glutinosa

1986 ◽  
Vol 64 (10) ◽  
pp. 2216-2226 ◽  
Author(s):  
Yves Prin ◽  
Mireille Rougier
Keyword(s):  
Cell Wall ◽  
Root Hair ◽  
Root Hairs ◽  
Root Apex ◽  
Alnus Glutinosa ◽  
Root Surface ◽  
Infection Process ◽  
Root Cap ◽  
A Cell ◽  
Histochemical Tests

The aim of the present study was to investigate the Alnus root surface using seedlings grown axenically. This study has focused on root zones where infection by the symbiotic actinomycete Frankia takes place. The zones examined extend from the root cap to the emerging root hair zone. The root cap ensheaths the Alnus root apex and extends over the root surface as a layer of highly flattened cells closely appressed to the root epidermal cell wall. These cells contain phenolic compounds as demonstrated by various histochemical tests. They are externally bordered by a thin cell wall coated by a thin mucilage layer. The root cap is ruptured when underlying epidermal cells elongate, and cell remnants are still found in the emerging root hair zone. Young emerging root hairs are bordered externally by a cell wall covered by a thin mucilage layer which reacts positively to the tests used for the detection of polysaccharides, glycoproteins, and anionic sites. The characteristics of the Alnus root surface and the biological function of mucilage and phenols present at the root surface are discussed in relation to the infection process.

Uniqueness

1996 ◽  
Author(s):  
Craig M. Bethke
Keyword(s):  
Geochemical Modeling ◽  
Theoretical Work ◽  
Input Constraints ◽  
Governing Equations ◽  
Single Root ◽  
Rate Laws ◽  
Starting Point ◽  
The Subject ◽  
Geochemical Models ◽  
Practical Question

A practical question that arises in quantitative modeling is whether the results of a modeling study are unique. In other words, is it possible to arrive at results that differ, at least slightly, from the original ones but nonetheless satisfy the governing equations and honor the input constraints? In the broadest sense, of course, no model is unique (see, for example, Oreskes et al., 1994). A geochemical modeler could conceptualize the problem differently, choose a different compilation of thermodynamic data, include more or fewer species and minerals in the calculation, or employ a different method of estimating activity coefficients. The modeler might allow a mineral to form at equilibrium with the fluid or require it to precipitate according to any of a number of published kinetic rate laws and rate constants, and so on. Since a model is a simplified version of reality that is useful as a tool (Chapter 2), it follows that there is no“correct” model, only a model that is most useful for a given purpose. A more precise question (Bethke, 1992) is the subject of this chapter: in geochemical modeling is there but a single root to the set of governing equations that honors a given set of input constraints? We might call such a property mathematical uniqueness, to differentiate it from the broader aspects of uniqueness. The property of mathematical uniqueness is important because once the software has discovered a root to a problem, the modeler may abandon any search for further solutions. There is no concern that the choice of a starting point for iteration has affected the answer. In the absence of a demonstration of uniqueness, on the other hand, the modeler cannot be completely certain that another solution, perhaps a more realistic or useful one, remains undiscovered. Geochemists, following early theoretical work in other fields, have long considered the multicomponent equilibrium problem (as defined in Chapter 3) to be mathematically unique. In fact, however, this assumption is not correct. Although relatively uncommon, there are examples of geochemical models in which more than one root of the governing equations satisfy the modeling constraints equally well. In this chapter, we consider the question of uniqueness and pose three simple problems in geochemical modeling that have nonunique solutions.

1. Foundations and structure of international law

2019 ◽  
pp. 1-20
Author(s):  
Anders Henriksen
Keyword(s):  
International Law ◽  
Legal System ◽  
Historical Overview ◽  
Public International Law ◽  
Legal Rules ◽  
System P ◽  
Rules And Principles ◽  
The Subject ◽  
International Legal System ◽  
The Relationship

This chapter introduces the subject of public international law and provides an overview of its most important elements. It begins with a brief historical overview of international law. It then presents the international legal system consisting of different structures of legal rules and principles; discusses the basis of international legal obligation; offers a brief overview of the relationship between international law and national law; and deals with the issue of enforcement. The chapter concludes with some remarks about the alleged inadequacies of international law and the tension between notions of justice and order that is so prevalent within the international legal system.

Land Law

2018 ◽  
Author(s):  
Ben McFarlane ◽  
Sarah Nield
Keyword(s):  
Detailed Knowledge ◽  
Land Trusts ◽  
Land Law ◽  
The Subject ◽  
Analytical Tools ◽  
Academic Debate

All books in this flagship series contain carefully selected substantial extracts from key cases, legislation, and academic debate, providing able students with a stand-alone resource. This edition of Land Law: Text, Cases, and Materials covers all core aspects of land law including legal estates, legal interests, equitable interests, acquisition of interests in land, trusts of land, the priority of interests in land, co-ownership and interests in the home, leases, easements, covenants, and security interests in land. The book provides students with the detailed knowledge and analytical tools required to understand and engage fully with the current topical debates surrounding the subject. The book comprises of a number of parts and it looks at the content question, the acquisition question, and priority and the defences question. It also considers the shared home, leases, neighbours and neighbourhoods (including easements, freehold covenants and flat ownership, including commonhold), and lastly security rights.

Economic Approaches to Regulation

2010 ◽  
pp. 16-38 ◽  
Author(s):  
Cento Veljanovski
Keyword(s):  
Legal System ◽  
Law And Economics ◽  
Competition Law ◽  
Regulatory Reform ◽  
Social Regulation ◽  
Economic Regulation ◽  
Economic Theories ◽  
System P ◽  
The Subject ◽  
Simple Economic

Economics has been at the heart of regulatory reform beginning with the wave of deregulation and privatisations of the 1980s. This article focuses on economic theories of regulation, and the way economics has been used to design and evaluate regulation. As the title of this article suggests, there are a number of economic approaches. However, these all share the conviction that relatively simple economic theory can assist in understanding regulation, and providing practical tools for regulators to make regulation more effective and efficient. The subject matter of the economics of regulation covers at least four broad areas — economic regulation, social regulation, competition law, and the legal system. Here a broader view is taken encompassing competition and merger laws, and the field known as law-and-economics or the economics of law is illustrated which looks at the legal system.

scholarly journals Domain-specific and cell type-specific localization of two types of cell wall matrix polysaccharides in the clover root tip.

1992 ◽  
Vol 118 (2) ◽  
pp. 467-479 ◽  
Author(s):  
M A Lynch ◽  
L A Staehelin
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Cellular Differentiation ◽  
Cortical Cell ◽  
Middle Lamella ◽  
Root Cap ◽  
Root Tip ◽  
Cortical Cells ◽  
Peripheral Cell ◽  
Clover Root

Using immunocytochemical techniques and antibodies that specifically recognize xyloglucan (anti-XG), polygalacturonic acid/rhamnogalacturonan I (anti-PGA/RG-I), and methylesterified pectins (JIM 7), we have shown that these polysaccharides are differentially synthesized and localized during cell development and differentiation in the clover root tip. In cortical cells XG epitopes are present at a threefold greater density in the newly formed cross walls than in the older longitudinal walls, and PGA/RG-I epitopes are detected solely in the expanded middle lamella of cortical cell corners, even after pretreatment of sections with pectinmethylesterase to uncover masked epitopes. These results suggest that in cortical cells XG and PGA/RG-I are differentially localized not only to particular wall domains, but also to particular cell walls. In contrast to their nonoverlapping distribution in cortical cells, XG epitopes and PGA/RG-I epitopes largely colocalize in the epidermal cell walls. The results also demonstrate that the middle lamella of the longitudinal walls shared by epidermal cells and by epidermal and cortical cells constitutes a barrier to the diffusion of cell wall and mucilage molecules. Synthesis of XG and PGA/RG-I epitope-containing polysaccharides also varies during cellular differentiation in the root cap. The differentiation of gravitropic columella cells into mucilage-secreting peripheral cells is marked by a dramatic increase in the synthesis and secretion of molecules containing XG and PGA/RG-I epitopes. In contrast, JIM 7 epitopes are present at abundant levels in columella cell walls, but are not detectable in peripheral cell walls or in secreted mucilage. There were also changes in the cisternal labeling of the Golgi stacks during cellular differentiation in the root tip. Whereas PGA/RG-I epitopes are detected primarily in cis- and medial Golgi cisternae in cortical cells (Moore, P. J., K. M. M. Swords, M. A. Lynch, and L. A. Staehelin. 1991. J. Cell Biol. 112:589-602), they are localized predominantly in the trans-Golgi cisternae and the trans-Golgi network in epidermal and peripheral root cap cells. These observations suggest that during cellular differentiation the plant Golgi apparatus can be both structurally and functionally reorganized.

A Pilot Study Applying Digital Radiography for Estimating Ratio of Supported Single-Root Surface Area

2005 ◽  
Vol 76 (2) ◽  
pp. 268-271 ◽  
Author(s):  
Ssu-Kuang Chen ◽  
Ju-Hung Pan ◽  
Chi-Hao Lin ◽  
Liang-Jenq Leu ◽  
Chung-Ming Chen ◽  
...  
Keyword(s):  
Pilot Study ◽  
Surface Area ◽  
Digital Radiography ◽  
Root Surface ◽  
Root Surface Area ◽  
Single Root

FACTORS GOVERNING ZOOSPORE RESPONSES OF PHYTOPHTHORA MEGASPERMA VAR. SOJAE TO PLANT ROOTS

1967 ◽  
Vol 45 (11) ◽  
pp. 1983-1994 ◽  
Author(s):  
H. H. Ho ◽  
C. J. Hickman
Keyword(s):  
Root Exudate ◽  
Chemical Nature ◽  
Root Surface ◽  
Plant Roots ◽  
Root Tip ◽  
Phytophthora Megasperma ◽  
Negative Pole ◽  
New Feature ◽  
Germ Tubes ◽  
Cyst Germination

In the presence of plant roots, zoospores of Phytophthora megasperma var. sojae reacted in general as do other fungal zoospores: they were attracted to, and trapped in the immediate vicinity of the root surface, on which they encysted rapidly. Encysted zoospores formed a continuous sheath around the root, thickest just behind the root tip. Cyst germination was stimulated. Germ tubes were always initiated from the side of cysts closest to the root and grew towards it. In addition, a new feature was observed, suppression of repeated emergence of zoospores. Zoospore accumulation was nonspecific with respect to host and non-host, resistance, and susceptibility.Tests with exudates and extracts from roots of resistant and susceptible soybean varieties and a non-host, pea, confirmed the chemical nature of the stimulus inducing these responses. Zoospores observed in an electric field were not attracted towards either pole, but they were trapped and encysted rapidly around the negative pole. Cyst germination was not stimulated. Nevertheless, since encystment was more pronounced on root exudate agar mounted on the negative pole, electric charges on roots may also contribute to inducing early encystment of zoospores there.In an investigation of ions on zoospore responses, with ionic resins, all phases of zoospore response to roots, with the exception of attraction, occurred in the presence of hydrogen resin particles.

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