Solute Transport in the Soil near Root Surfaces

2000 ◽  
Author(s):  
Peter B. Tinker ◽  
Peter Nye
Keyword(s):  
Soil Solution ◽  
Dynamic Equilibrium ◽  
Pore Solution ◽  
Plant Root ◽  
Unit Length ◽  
Solution Concentration ◽  
Root Surface ◽  
Transport Processes ◽  
Soil Pores ◽  
Intact Root

We discussed in chapter 4 the movement of solute between small volumes of soil, and in chapter 5 some properties of plant roots and associated hairs, particularly the relation between the rate of uptake at the root surface and the concentration of solute in the ambient solution. In the chapters to follow, we consider the plant root in contact with the soil, and deal with their association in increasingly complex situations; first, when the root acts merely as a sink and, second, when it modifies its relations with the surrounding soil by changing its pH, excreting ions, stimulating microorganisms, or developing mycorrhizas. In this chapter, we take the simplest situation that can be studied in detail, namely, a single intact root alone in a volume of soil so large that it can be considered infinite. The essential transport processes occurring near the root surface are illustrated in figure 6.1. We have examined in chapter 3 the rapid dynamic equilibrium between solutes in the soil pore solution and those sorbed on the immediately adjacent solid surfaces. These sorbed solutes tend to buffer the soil solution against changes in concentration induced by root uptake. At the root surface, solutes are absorbed at a rate related to their concentration in the soil solution at the boundary (section 5.3.2); and the root demand coefficient, αa, is defined by the equation . . . I = 2παaCLa (6.1) . . . where I = inflow (rate of uptake per unit length), a = root radius, CLa = concentration in solution at the root surface. To calculate the inflow, we have to know CLa, and the main topic of this chapter is the relation between CLa, and the soil pore solution concentration CL. The root also absorbs water at its surface due to transpiration (chapter 2) so that the soil solution flows through the soil pores, thus carrying solutes to the root surface by mass flow (convection). Barber et al. (1962) calculated whether the nutrients in maize could be acquired solely by this process, by multiplying the composition of the soil solution by the amount of water the maize had transpired.

scholarly journals The impact of four decades of annual nitrogen addition on dissolved organic matter in a boreal forest soil

2013 ◽  
Vol 10 (3) ◽  
pp. 1365-1377 ◽  
Author(s):  
M. O. Rappe-George ◽  
A. I. Gärdenäs ◽  
D. B. Kleja
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Soil Solution ◽  
Mineral Soil ◽  
Solution Concentration ◽  
Oxidative Enzymes ◽  
N Saturation ◽  
N Addition ◽  
Mineral N ◽  
The Impact

Abstract. Addition of mineral nitrogen (N) can alter the concentration and quality of dissolved organic matter (DOM) in forest soils. The aim of this study was to assess the effect of long-term mineral N addition on soil solution concentration of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) in Stråsan experimental forest (Norway spruce) in central Sweden. N was added yearly at two levels of intensity and duration: the N1 treatment represented a lower intensity but a longer duration (43 yr) of N addition than the shorter N2 treatment (24 yr). N additions were terminated in the N2 treatment in 1991. The N treatments began in 1967 when the spruce stands were 9 yr old. Soil solution in the forest floor O, and soil mineral B, horizons were sampled during the growing seasons of 1995 and 2009. Tension and non-tension lysimeters were installed in the O horizon (n = 6), and tension lysimeters were installed in the underlying B horizon (n = 4): soil solution was sampled at two-week intervals. Although tree growth and O horizon carbon (C) and N stock increased in treatments N1 and N2, the concentration of DOC in O horizon leachates was similar in both N treatments and control. This suggests an inhibitory direct effect of N addition on O horizon DOC. Elevated DON and nitrate in O horizon leachates in the ongoing N1 treatment indicated a move towards N saturation. In B horizon leachates, the N1 treatment approximately doubled leachate concentrations of DOC and DON. DON returned to control levels, but DOC remained elevated in B horizon leachates in N2 plots nineteen years after termination of N addition. We propose three possible explanations for the increased DOC in mineral soil: (i) the result of decomposition of a larger amount of root litter, either directly producing DOC or (ii) indirectly via priming of old SOM, and/or (iii) a suppression of extracellular oxidative enzymes.

scholarly journals Developing a method for real-time visualization of cellulase activity

2020 ◽  
Author(s):  
Pallavi Kumari ◽  
Tali Sayas ◽  
Patricia Bucki ◽  
Sigal Brown Miyara ◽  
Maya Kleiman
Keyword(s):  
Real Time ◽  
Plant Cell Wall ◽  
Plant Root ◽  
Cellulase Activity ◽  
Root Surface ◽  
Surface Microstructure ◽  
Root Extract ◽  
Cell Wall Degrading Enzymes ◽  
Real Time Visualization ◽  
Replication Technique

AbstractStudying the interactions between microorganisms and plant roots is crucial for understanding a variety of phenomena concerning crop yield and health. The role of root surface properties in these interactions, is rarely addressed. To this end, we previously built a synthetic system, from the inert polymer polydimethyl siloxane (PDMS), mimicking the root surface microstructure, using a replication technique. This replica enables the study of isolated effects of surface structure on microorganism-plant interactions. Since the root surface is composed mostly of cellulose, using cellulose-like materials as our replica, instead of PDMS, is the next logical step. This will enable following the hydrolysis of such surfaces as a result of microorganisms secreting Plant Cell Wall Degrading Enzymes (PCWDE), and in particular, cellulase. Visualization of such hydrolysis in a synthetic system can assist in studying the localization and activity of microorganisms and how they correlate with surface microtopography, separately from chemical plant signals.In this work, we modified the known carboxymethyl cellulase (CMC) hydrolysis visualization method to enable real-time tracking of cellulase activity of microorganisms on the surface. Surface was formed from pure CMC, rather than CMC incorporated in agar as is often done, and by that, eliminating diffusion issues. Acridine orange dye, which is compatible, at low concentrations, with microorganisms, as opposed to other routinely used dyes, was incorporated into the film. The dye disassociated from the film when hydrolysis occurred, forming a halo surrounding the point of hydrolysis. This enabled real-time visualization since the common need for post hydrolysis dyeing was negated. Using Root Knot Nematode (RKN) as a model organism that penetrates the plant root, we showed it was possible to follow microorganism cellulase secretion on the surface in the form of CMC film hydrolysis. Furthermore, the addition of natural additives, in the form of root extract was also shown to be an option and resulted in an increased RKN response. We tested our newly developed method by changing temperature and pH conditions and by characterization of the hydrolyzed surface using both Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM).This method will be implemented in the future on a root surface microstructure replica. We believe the combination of this new method with our previously developed root surface microstructure replication technique can open a new avenue of research in the field of plant root-microorganism interactions.

scholarly journals Low, Controlled Nutrient Availability Provided by Organic Waste Materials for Chrysanthemum

1992 ◽  
Vol 117 (3) ◽  
pp. 422-429 ◽  
Author(s):  
Kimberly A. Williams ◽  
Paul V. Nelson
Keyword(s):  
Soil Solution ◽  
Release Rate ◽  
Waste Water Treatment ◽  
Poultry Manure ◽  
Solution Concentration ◽  
Application Rate ◽  
Liquid Fertilizer ◽  
Brevibacterium Lactofermentum ◽  
N Release ◽  
Poultry Feathers

Seven organic materials including 1) the bacterium Brevibacterium lactofermentum (Okumura et al.) in a nonviable state, 2) a mixture of two bacteria, Bacillus licheniformis (Weigmann) and Bacillus subtilis (Ehrenberg), plus the fungus Aspergillus niger (van Tieghem) in a nonviable state, 3) an activated microbial sludge from waste-water treatment, 4) sludge from a poultry manure methane generator, 5) unsteamed bonemeal, 6) aged pine needles, and 7) poultry feathers were evaluated to determine their pattern and term of N release and the possibility of using them as an integral part of root media releasing N at a steady, low rate over 10 to 12 weeks for production of Dendranthema × grandiflorum (Ramat.) Kitamura `Sunny Mandalay'. These were compared to the inorganic slow-release fertilizer micro Osmocote (17N-3.9P-10.8K) and a weekly liquid fertilizer control. All organic sources released N most rapidly during the first 2 weeks, followed by a decline, which ended at 6 to 7 weeks. Brevibacterium lactofermentum, bonemeal, and micro Osmocote treatments resulted in about equal growth, which was similar to growth of a weekly liquid fertilizer control for 9 weeks in the first and for 12 weeks in the second experiment. The period of N release could not be extended through increased application rate of source due to the high initial release rate. It was not possible to lower source application rates to achieve an effective, low soil solution concentration due to the large variation in release rate over time. Efficiency of N use varied among plants grown in media treated with various microorganismal sources and was highest in those treated with B. lactofermentum. Nitrogen release from ground poultry feathers was inadequate, and additions of the viable hydrolyzing bacterium B. licheniformis to feathers failed to increase soil solution N levels. Attempts to retard mineralization of B. lactofermentum by cross-linking proteins contained within the bacterium by means of heat treatment at 116C vs. 82C failed. While anaerobic poultry manure sludge proved to be an inefficient source of N, it provided large amounts of P. Organic sources released primarily ammoniacal N, which raised the medium pH by as much as one unit, necessitating the use of less limestone in the medium formulation.

Einfluss der elektrochemischen Doppelschicht auf die Sorption und den Transport von Chlorionen im Zementstein / Influence of the electrochemical double layer on sorption and transport of chlorides in hardened cement paste

2000 ◽  
Vol 6 (4) ◽  
pp. 415-428
Author(s):  
O. Wowra ◽  
M.J. Setzer
Keyword(s):  
Double Layer ◽  
Cement Paste ◽  
Building Materials ◽  
Pore Solution ◽  
Chloride Ions ◽  
Transport Processes ◽  
Cement Matrix ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Electrochemical Double Layer

Abstract Besides the formation of Friedel salt the transport and binding of chlorides in concrete is mainly defined by the electrochemical double layer at the interface between cement matrix and pore solution. Due to the alkaline pore solution the surface of hardened cement paste is negatively charged which may change to positive values by the potential regulating calcium ions. Inverting of the surface charge leads to an attraction of anions and therefore, to an adsorption of chloride ions in the diffuse part of the electrochemical double layer. Influence from outside like sulphates and carbon dioxide may lead to a decomposition of Friedel salt. Apart from these effect temperature, pH-value and certain environmental conditions affects the electrochemical double layer as well. The chloride equilibrium is mainly controlled by adsorbed ions in the electrochemical double layer. The model presented here is relevant for the assessment of ion transport processes in mineral building materials. Continuing investigations may lead to optimize transport models and a better evaluation of the critical chloride threshold value in reinforced concrete.

scholarly journals Hypothetical Protein Avin_16040 as the S-Layer Protein of Azotobacter vinelandii and Its Involvement in Plant Root Surface Attachment

2015 ◽  
Vol 81 (21) ◽  
pp. 7484-7495 ◽  
Author(s):  
Pauline Woan Ying Liew ◽  
Bor Chyan Jong ◽  
Nazalan Najimudin
Keyword(s):  
Cell Surface ◽  
Deletion Mutant ◽  
Azotobacter Vinelandii ◽  
Plant Root ◽  
Hypothetical Protein ◽  
Surface Hydrophobicity ◽  
Root Surface ◽  
Bacterial Cells ◽  
Wild Type ◽  
Content Type

ABSTRACTA proteomic analysis of a soil-dwelling, plant growth-promotingAzotobacter vinelandiistrain showed the presence of a protein encoded by the hypotheticalAvin_16040gene when the bacterial cells were attached to theOryza sativaroot surface. AnAvin_16040deletion mutant demonstrated reduced cellular adherence to the root surface, surface hydrophobicity, and biofilm formation compared to those of the wild type. By atomic force microscopy (AFM) analysis of the cell surface topography, the deletion mutant displayed a cell surface architectural pattern that was different from that of the wild type.Escherichia colitransformed with the wild-typeAvin_16040gene displayed on its cell surface organized motifs which looked like the S-layer monomers ofA. vinelandii. The recombinantE. colialso demonstrated enhanced adhesion to the root surface.

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