Transport of Tritiated Water and 14c-Labelled Assimilate Into Grains of Wheat. III. Diffusion of Tho Through the Stalk

1985 ◽  
Vol 12 (6) ◽  
pp. 595 ◽  
Author(s):  
CF Jenner
Keyword(s):  
Mass Flow ◽  
Short Distance ◽  
Vascular System ◽  
Tritiated Water ◽  
The Self ◽  
Wheat Grain ◽  
Physical Processes ◽  
Self Diffusion ◽  
Separate System ◽  
Flow Through

Measuring the rate at which tritiated water is transported by diffusion through the stalk of the wheat grain is the main purpose of this paper. Diffusion of THO through the stalk is much slower than expected on the basis of the self-diffusion of THO in water, demonstrating that there are substantial resistances to diffusion of water in the stalk. Entry of THO into the grain by physical processes alone (diffusion), as measured in assemblies in which the grain (stripped of its bracts) is sealed into an impermeable capsule, is fast enough to account for the observed rate of transport of THO into normally functioning grains. Metabolically linked transport of water through the stalk is not detectable. Either the volume of water involved in mass flow through the stalk is too low to be detectable - which would require the concentration of sucrose to be about 2 M, or the entry of assimilate is not accompanied by water. Short-distance transfer of solute (only) from the plant's vascular system to a separate system servicing the grain seems the simplest explanation on the basis of the available evidence.

Transport of Tritiated Water and 14C-Labelled Assimilate Into Grains of Wheat. II. Independence of Entry of 14c-Labelled Assimilate and THO

1985 ◽  
Vol 12 (6) ◽  
pp. 587 ◽  
Author(s):  
CF Jenner
Keyword(s):  
Mass Flow ◽  
Tritiated Water ◽  
Grain Filling ◽  
Transport Mechanisms ◽  
Hot Wire ◽  
Wheat Grain ◽  
Pressure Driven

The mechanism involved in the transport of assimilates through the stalk by which the grain is attached to the rachilla has been investigated. Based on the presumption of pressure-driven mass flow, treatments designed to inhibit the import of assimilates would be expected to inhibit also the entry of water into the grain. Detached ears were supplied with solutions of [14C]sucrose in tritiated water (THO), and ears attached to the plant were watered with THO and supplied with 14CO2. The rachilla was heated by contact with a hot wire, and the stalk by steam-girdling. In addition, dinitrophenol (DNP) was used as an inhibitor of metabolically linked transport mechanisms. Heating or treatment with DNP reduced the transport of [14C]sucrose or [14C]-labelled assimilate into the grain, but the entry of THO was not reduced even by treatments which abolished altogether the transport of 14C into the grain. These results cannot be reconciled with mass flow as the means of transporting assimilates through the stalk of the wheat grain during grain filling.

scholarly journals Evolution and palaeophysiology of the vascular system and other means of long-distance transport

2017 ◽  
Vol 373 (1739) ◽  
pp. 20160497 ◽  
Author(s):  
John A. Raven
Keyword(s):  
Mass Flow ◽  
Vascular System ◽  
Terrestrial Ecosystem ◽  
Arbuscular Mycorrhizas ◽  
Organic Solutes ◽  
Long Distance ◽  
Long Distance Transport ◽  
Structural Details ◽  
Flow Through ◽  
And Storage

Photolithotrophic growth on land using atmospheric CO 2 inevitably involves H 2 O vapour loss. Embryophytes greater than or equal to 100 mm tall are homoiohydric and endohydric with mass flow of aqueous solution through the xylem in tracheophytes. Structural details in Rhynie sporophytes enable modelling of the hydraulics of H 2 O supply to the transpiring surface, and the potential for gas exchange with the Devonian atmosphere. Xylem carrying H 2 O under tension involves programmed cell death, rigid cell walls and embolism repair; fossils provide little evidence on these functions other than the presence of lignin. The phenylalanine ammonia lyase essential for lignin synthesis came from horizontal gene transfer. Rhynie plants lack endodermes, limiting regulation of the supply of soil nutrients to shoots. The transfer of organic solutes from photosynthetic sites to growing and storage tissues involves mass flow through phloem in extant tracheophytes. Rhynie plants show little evidence of phloem; possible alternatives for transport of organic solutes are discussed. Extant examples of the arbuscular mycorrhizas found in Rhynie plants exchange soil-derived nutrients (especially P) for plant-derived organic matter, involving bidirectional mass flow along the hyphae. The aquatic cyanobacteria and the charalean Palaeonitella at Rhynie also have long-distance (relative to the size of the organism) transport. This article is part of a discussion meeting issue ‘The Rhynie cherts: our earliest terrestrial ecosystem revisited’.

Variation in the wheat intake of individual sheep measured by use of labelled grain: behavioural influences

1981 ◽  
Vol 21 (111) ◽  
pp. 395 ◽  
Author(s):  
E Juwarini ◽  
B Howard ◽  
BD Siebert ◽  
JJ Lynch ◽  
RL Elwin
Keyword(s):  
Dominance Hierarchy ◽  
Tritiated Water ◽  
Supplementary Feeding ◽  
Previous Experience ◽  
Feed Consumption ◽  
Wheat Grain ◽  
Accurate Calculation ◽  
Early Introduction

A preliminary experiment with sheep in pens demonstrated that wheat grain could be labelled with tritiated water so that when fed it could provide data that would allow accurate calculation of individual feed consumption. This techinque was used with two groups of sheep fed supplementary wheat grain in paddocks. Half of the animals had previous experience of grain feeding some eight months earlier and the others had not eaten grain. Individual diversity of intake could be estimated usefully by tritium labelling of wheat, which was fed to the sheep in a group. The experiment showed that there was a threefold difference in the amount of wheat eaten between the lowest and highest intakes. Further, animals with previous experience of grain feeding consumed the entire ration initially, but those without previous experience did not consume all of the ration until two weeks after wheat feeding began. Over the period of measurement the experienced sheep consumed about 13% more wheat than the non-experienced group. There were insufficient aggressive acts to establish a dominance hierarchy in either group, although the experienced sheep were more aggressive than the others. Aggressiveness by one sheep towards other sheep did not result in higher wheat intakes by the former compared with other sheep in the group. The results are discussed in terms of the variability in acceptance of such supplements by animals, and of the value, later in life, of early introduction of supplementary feeding.

scholarly journals Self-diffusion scalings in dense granular flows

Soft Matter ◽  
2021 ◽  
Author(s):  
Riccardo Artoni ◽  
Michele Larcher ◽  
James T. Jenkins ◽  
Patrick Richard
Keyword(s):  
Shear Rate ◽  
Solid Fraction ◽  
Granular Flows ◽  
The Self ◽  
Granular Temperature ◽  
Restitution Coefficient ◽  
Self Diffusion ◽  
Diffusivity Tensor ◽  
Dense Granular Flows

The self-diffusivity tensor in homogeneously sheared dense granular flows is anisotropic. We show how its components depend on solid fraction, restitution coefficient, shear rate, and granular temperature.

scholarly journals Self-Diffusion Coefficients, Aggregation Numbers and the Range of Existence of Spherical Micelles of Oxyethylated Alkylphenols

2021 ◽  
Author(s):  
Victor P. Arkhipov ◽  
Natalia A. Kuzina ◽  
Andrei Filippov
Keyword(s):  
Aqueous Solutions ◽  
Diffusion Coefficients ◽  
The Self ◽  
Self Diffusion ◽  
Aggregation Numbers ◽  
Temperature Ranges ◽  
Spherical Micelles ◽  
Limiting Values

AbstractAggregation numbers were calculated based on measurements of the self-diffusion coefficients, the effective hydrodynamic radii of micelles and aggregates of oxyethylated alkylphenols in aqueous solutions. On the assumption that the radii of spherical micelles are equal to the lengths of fully extended neonol molecules, the limiting values of aggregation numbers corresponding to spherically shaped neonol micelles were calculated. The concentration and temperature ranges under which spherical micelles of neonols are formed were determined.

Direct determination of the self-diffusion mechanism in bccβ-titanium

1989 ◽  
Vol 39 (8) ◽  
pp. 5025-5034 ◽  
Author(s):  
G. Vogl ◽  
W. Petry ◽  
Th. Flottmann ◽  
A. Heiming
Keyword(s):  
Diffusion Mechanism ◽  
Direct Determination ◽  
The Self ◽  
Self Diffusion

scholarly journals Background Pressure Effects on the Performance of a 20 kW Magnetically Shielded Hall Thruster Operating in Various Configurations

Aerospace ◽  
2021 ◽  
Vol 8 (3) ◽  
pp. 69
Author(s):  
Antonio Piragino ◽  
Farbod Faraji ◽  
Maryam Reza ◽  
Eugenio Ferrato ◽  
Annalisa Piraino ◽  
...  
Keyword(s):  
Mass Flow ◽  
Discharge Current ◽  
Pressure Effects ◽  
Hall Thruster ◽  
Physical Processes ◽  
Linear Behavior ◽  
Mass Flow Rates ◽  
Anode Mass ◽  
Lower Background ◽  
Operating Regimes

The paper reports the characterization results of a 20 kW-class magnetically shielded Hall thruster in three different configurations and operating with a centrally mounted cathode. The characterization was carried out at two different pumping speeds in SITAEL’s IV10 vacuum chamber, resulting in two different background pressure levels for each tested operating point. A linear behavior of discharge current and thrust values versus the anode mass flow rate was noticed for both pumping speeds levels and for all the three configurations. In addition, the thrust and discharge current values were always found to be lower at lower background pressure levels. From the performance levels, a preliminary estimate of the ingested mass flow rates was performed, and the values were then compared to a recently developed background flow model. The results suggested that, for this thruster and in the tested operating regimes, the change in performance due to background pressure could be ascribed not only to the ingestion of external mass flow coming from the chamber but also to other physical processes caused by the flux of residual background neutrals.

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