Translocation velocity and specific mass transfer in the sieve tubes of Fraxinus americana L.

Planta ◽  
1969 ◽  
Vol 84 (3) ◽  
pp. 272-278 ◽  
Author(s):  
Martin H. Zimmermann
Keyword(s):  
Mass Transfer ◽  
Specific Mass ◽  
Fraxinus Americana ◽  
Sieve Tubes ◽  
Translocation Velocity

Specific Mass Transfer and Sink-Controlled Phloem Translocation in Castor Bean

1984 ◽  
Vol 11 (6) ◽  
pp. 483 ◽  
Author(s):  
J Kallarackal ◽  
JA Milburn
Keyword(s):  
Mass Transfer ◽  
Sap Flow ◽  
Ricinus Communis ◽  
Turgor Pressure ◽  
Back Pressure ◽  
Limiting Factor ◽  
Specific Mass ◽  
Phloem Sap ◽  
Phloem Translocation ◽  
Sieve Tubes

The specific mass transfer (SMT) into the fruits of Ricinus communis was measured in three different systems: (1) the intact truss, (2) fruit-thinned truss (all but one fruit removed), and (3) exuding peduncle. We found that the SMT in an intact system accords well with values reported in previous studies. But in the single-fruit and exuding systems the values were 2 and 18 times higher than the intact system, respectively. The inability of a single fruit to achieve a much higher SMT value shows that the assimilate unloading is sink-controlled. The high SMT value of the exuding system demonstrates the capacity of the sieve tubes to transport large volumes of phloem sap when turgor pressure in the sieve tubes at the sink ceases to be a limiting factor. This can be contrasted with the single-fruit system where the sink probably exerts a 'back pressure' while the assimilate supply is unlimited. The twofold increase in SMT shown by a single-fruit system is probably caused by hormone-stimulated assimilate unloading. SMT values have been used also to calculate the velocity of sap flow in the sieve tubes.

Functioning of Conducting Elements of Phloem and Xylem in the Stalk of the Developing Fruit of Lupinus albus L

1978 ◽  
Vol 5 (3) ◽  
pp. 321 ◽  
Author(s):  
JS Pate ◽  
J Kuo ◽  
PJ Hocking
Keyword(s):  
Mass Transfer ◽  
Dry Matter ◽  
Xylem Sap ◽  
Cross Sectional Area ◽  
White Lupin ◽  
Sectional Area ◽  
Weight Changes ◽  
Specific Mass ◽  
Cross Sectional ◽  
Sieve Tubes

The economy of water and dry matter in fruits of white lupin (L. albus L.) was studied by measuring transpiration, CO2 exchange and weight changes over an 8-week growth period. These data were combined with analyses of upper stem tracheal (xylem) sap and fruit tip phloem sap to estimate rates of import of dry matter and water through xylem and phloem. Assuming unidirectional mass flow to operate, phloem carried 97 % of the dry matter and 27 % of the water entering the fruit, and xylem supplied the remainder of the water, 30 % of the minerals and 10 % of the amino compounds. The structure of fruit stalks of various age was examined by light microscopy. Cross-sectional areas occupied by different tissues were measured, and numbers and mean transverse areas of conducting elements estimated. Sieve tubes comprised 0.66-1.13% of the stalk's cross-sectional area, vessels plus tracheids 0.27 - 0.50%. Secondary xylem consisted mainly of fibres. Sieve tubes occupied 18 - 27% of the phloem cross-sectional area. The fully grown stalk showed approximately three times as many sieve tubes in transverse section as vessels plus tracheids. Transfer of dry matter and water through the fruit stalk was highest during the exponential phase of fruit growth. Peak specific mass transfer in sieve tubes was 3.95 g dry matter per square centimetre of sieve tube per hour, in tracheids plus vessels 0.28 g cm2 h-1. Maximum flow velocity in sieve tubes was 22 cm h-1, in tracheids plus vessels, 147 cm h-1. Values for specific mass transfer and flow velocities were several times less in stalks of very young or near-mature fruits.

Numerical Simulation of Supercritical Extraction Processes

2009 ◽  
Vol 4 (4) ◽  
Author(s):  
Carlos Manuel Silva ◽  
Claudia P Passos ◽  
Manuel A. Coimbra ◽  
Francisco A. Da Silva F.
Keyword(s):  
Mass Transfer ◽  
Method Of Lines ◽  
Supercritical Extraction ◽  
Specific Mass ◽  
Experimental Conditions ◽  
The Method Of Lines ◽  
Extraction Unit ◽  
Extraction Processes ◽  
Operating Regimes ◽  
Matrix Series

A mathematical model with two different methods to represent the mass transfer in the biomass matrix, (series and parallel) is proposed to simulate a supercritical extraction unit. The model is solved using the method of lines and finite differences with flow correction. Using experimental extraction curves, both models were fitted fairly well, with equivalent accuracy. Two operating regimes were detected in the selected experimental conditions: equilibrium and mass transfer controlled. The last one is more difficult to simulate, requiring specific mass transfer parameters for series and parallel alternatives, for its accurate representation.

scholarly journals Atenolol removal by nanofiltration: a case-specific mass transfer correlation

2020 ◽  
Vol 81 (2) ◽  
pp. 210-216 ◽  
Author(s):  
Alexandre Giacobbo ◽  
Elisa Veridiani Soares ◽  
Andréa Moura Bernardes ◽  
Maria João Rosa ◽  
Maria Norberta de Pinho
Keyword(s):  
Mass Transfer ◽  
Membrane Fouling ◽  
Concentration Polarization ◽  
Membrane Separation ◽  
Film Theory ◽  
Operating Conditions ◽  
Transfer Coefficients ◽  
Specific Mass ◽  
Mass Transfer Coefficients ◽  
Mass Transfer Correlation

Abstract Concentration polarization is a phenomenon inherent to membrane separation operations and as a precursor of membrane fouling is frequently related to the decrease in the performance of these operations. In the present work, a case-specific mass transfer correlation was developed to assess the concentration polarization when nanofiltration, in different operating conditions, was applied to treat a pharmaceutical wastewater containing atenolol. NF runs with two membranes, two atenolol concentrations and three feed circulating velocities were conducted, and the corresponding experimental mass transfer coefficients were determined using film theory to describe the concentration polarization phenomenon. Higher velocities led to higher mass transfer coefficients and, consequently, lower concentration polarization. These mass transfer coefficients were correlated with the circulating velocity (Re), the solute diffusivity (Sc) and the membrane permeability (LP+) (the membrane is a permeable interface with effect on the concentration profiles developed from the interface towards the bulk feed), yielding the following correlation Sh = 1.98 × 104Re0.5Sc0.33LP+0.32. The good agreement between the calculated and the experimental results makes this correlation a valuable tool for water practitioners to predict and control the concentration polarization during atenolol-rich wastewater treatment by nanofiltration, thereby increasing its productivity and selectivity.

Contractile proteins and hypotheses concerning their role in phloem transport

1980 ◽  
Vol 58 (7) ◽  
pp. 826-832 ◽  
Author(s):  
David P. Aikman
Keyword(s):  
Mass Transfer ◽  
Experimental Evidence ◽  
Strong Evidence ◽  
Cytoplasmic Streaming ◽  
Unit Length ◽  
Phloem Transport ◽  
Surface Flow ◽  
Specific Mass ◽  
Higher Power ◽  
Atpase System

Contractile and motile proteins have been found in plants. Cytoplasmic streaming in Nitella is not inconsistent with several aspects of an actinomyosin system. Several hypotheses have been advanced, invoking the participation of contractile or motile proteins in phloem transport. The peristalsis hypothesis lacks credibility in absence of strong evidence of existence of sufficiently large tubules. Microperistalsis could be responsible for only a small fraction of the specific mass transfer and may require a faster reaction frequency than acceptable for an ATPase system. Undulating filaments would appear to require a much higher power per unit length than could be generated by actinomyosin. Since electroosmosis and surface flow have already been discounted, the Münch hypothesis must be favoured although not all observational or experimental evidence by any means supports it.

Sieve tube longevity in white ash (Fraxinus americana) studied with a new histochemical test for the identification of sugar

1979 ◽  
Vol 57 (6) ◽  
pp. 650-656 ◽  
Author(s):  
E. Zamski ◽  
M. H. Zimmermann
Keyword(s):  
Sieve Tube ◽  
Cambial Activity ◽  
Fraxinus Americana ◽  
Starch Grains ◽  
Active Season ◽  
White Ash ◽  
Histochemical Test ◽  
Short Period ◽  
Young Leaves ◽  
Sieve Tubes

A histochemical test for functioning sieve tubes, based on the 5-diazouracil sugar reaction, has been used to identify functioning sieve tubes in Fraxinus americana L. The plant material was lyophilized, treated with the reagent, and sectioned in a cryostat. Before the resumption of cambial activity, when buds are still closed (late April – early May), starch grains of the storage tissues in bark and wood disappear and rays, cambrium, and phloem are loaded with sugars. In early spring, sugars begin to accumulate in last year's sieve tubes, especially in those which had not been fully differentiated in the previous active season and those which were functioning but had formed toward the end of the active season. Girdling experiments, carried out during May, showed that translocation in the phloem does occur, to some extent, during the period when the buds develop and the young leaves grow. The reactivated sieve tubes provide the channel of translocation to developing buds for sugars, formed of the dissolution of starch grains. The first early-phloem sieve tubes are formed at the end of May and loaded with sugars during June. There seems to be a short period of simultaneous import into young leaves via reactivated phloem and export via new phloem. After this, last year's sieve tubes are crushed. A noticeable pressure flow does not appear in the main stem until mid-June.

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