How do newly matured vessels start conducting water? The significance of lateral pathways for connecting newly matured vessels to the transpiration stream

2019 ◽  
Vol 39 (4) ◽  
pp. 641-649
Author(s):  
Youcef Halis ◽  
Mohammed L Benhaddya ◽  
Hocine Bensaha ◽  
Mohamed M Senoussi
Keyword(s):  
Transpiration Stream

The Xylem Sap of Maize Roots: Its Collection, Composition and Formation

1988 ◽  
Vol 15 (4) ◽  
pp. 557 ◽  
Author(s):  
MJ Canny ◽  
ME Mccully
Keyword(s):  
Amino Acids ◽  
Organic Acids ◽  
Organic Acid ◽  
Aspartic Acid ◽  
Xylem Sap ◽  
Great Variability ◽  
Reduced Pressure ◽  
Transpiration Stream ◽  
Maize Roots ◽  
Total Amino Acids

Three methods of sampling xylem sap of maize roots were compared: sap bleeding from the stem cut just above the ground; sap bleeding from the cut tops of roots still undisturbed in the ground; and sap aspirated from excavated roots under reduced pressure. The bleeding saps were often unobtainable. When their composition was measured with time from cutting, the concentrations of the major solutes approximately doubled in 2 h. Aspirated sap was chosen as the most reliable sample of root xylem contents. Solute concentrations of the saps showed great variability between individual roots for all solutes, but on average the concentrations found (in �mol g-1 sap) were: total amino acids, 1.8; nitrate, 1.8; sugars (mainly sucrose), 5.4; total organic acids, 18.3. Individual amino acids also varied greatly between roots. Glutamine, aspartic acid and serine were generally most abundant. The principal organic acid found was malic, approximately 8 �mol g-1. From these analyses the ratios of carbon in the fractions (sugars : amino acids : organic acids) = (44 : 6 : 50). 14Carbon pulse fed to a leaf appeared in the root sap within 30 min, rose to a peak at 4-6 h, and declined slowly over a week. During all this time the neutral, cation and anion fractions were sensibly constant in the proportions 86 : 10 : 4. The 14C therefore did not move towards the equilibrium of 12C-compounds in the sap. It is argued that the results do not support a hypothesis of formation of amino carbon from recent assimilate and reduced nitrate in the roots and an export of this to the shoot in the transpiration stream.

A Microradioautographic Study of 14C-Diuron Absorption by Cotton

Weed Science ◽  
1971 ◽  
Vol 19 (4) ◽  
pp. 355-362 ◽  
Author(s):  
R. H. Strang ◽  
R. L. Rogers
Keyword(s):  
Gossypium Hirsutum ◽  
Cotton Plant ◽  
Freeze Drying ◽  
Effective Concentration ◽  
Transpiration Stream ◽  
Pigment Glands

The techniques of cryostat sectioning, freeze-drying, and microradioautography were adapted to study the absorption and translocation of radio-labeled 3-(3,4-dichlorophenyl)-1,1-dimethylurea (14C-diuron) in root-treated cotton (Gossypium hirsutum L., var. Coker 201) plants. Diuron appeared to move primarily in the apoplast and to be transported acropetally and laterally in the transpiration stream. Radioactivity was observed to accumulate in striking concentrations in the lysigenous, or pigment, glands and the trichomes of the cotton plant. This accumulation is postulated to be a major factor in lowering the effective concentration of the herbicide in the leaves of cotton as compared to leaves of more susceptible plants, and thus may be a significant factor in the tolerance of cotton to diuron.

Mediation of rapid electrical, metabolic, transpirational, and photosynthetic changes by factors released from wounds. I. Variation potentials and putative action potentials in intact plants

1976 ◽  
Vol 54 (23) ◽  
pp. 2642-2650 ◽  
Author(s):  
Jerome W. Van Sambeek ◽  
Barbara G. Pickard
Keyword(s):  
Action Potentials ◽  
Chemical Substance ◽  
Variation Potential ◽  
Transpiration Stream ◽  
Single Leaf ◽  
Intact Plants

Damaging representative plants from five angiosperm families by heating or crushing a small portion of a single leaf results in an electrical change which may spread throughout the shoot. In Mimosa, similar changes have previously been identified as variation potentials.Except in one of the five plants, a variation potential is often accompanied by brief fluctuations which may propagate either basipetally or acropetally and which have many of the properties of action potentials.The spread of a variation potential as described in Mimosa is due to the concommitant spread of a chemical substance in the transpiration stream. In this paper, it is shown that the spread of the purported variation potential is compatible with movement of material in the transpiration stream. In the next paper causation by a substance or group of substances, at present called Ricca's factor, is demonstrated.

The transpiration stream in the leaf apoplast: water and solutes

1993 ◽  
Vol 341 (1295) ◽  
pp. 87-100 ◽  
Keyword(s):  
Cell Wall ◽  
Cell Membranes ◽  
Gradient Flow ◽  
Pressure Vessels ◽  
Water Soluble ◽  
Fluorescent Tracers ◽  
Transpiration Stream ◽  
Cell Wall Apoplast ◽  
Flow Through ◽  
High Concentrations

Flow of the transpiration stream in the lumen apoplast of the xylem appears hydrodynamically orthodox in being approximately described by the Hagen-Poiseuille Law, and by Murray’s Law for branching pipes. Flow may be followed in the major (supply) veins by labelling the stream with dye solutions. Progress of the dye in the stream into the minor (distribution) veins is obscured by surrounding tissues. Observations of the spread of fluorescent tracers from these veins in living leaves gave results that have been seriously misinterpreted to present a false view of the cell wall apoplast. Microscopy of the stabilized water-soluble fluorescent tracers moving out of the minor veins has revealed that: (i) the dye is separated from the water by filtration through cell membranes, and the water moves through the symplast; and (ii) the dye diffuses in the cell wall apoplast at rates 1/100 to 1/10 000 the rate of diffusion in water. As a consequence of (i), high concentrations of dye build up at sites called sumps. In grasses these sumps may be in the intercellular spaces outside the xylem. In dicotyledons these sumps are within the small tracheary elements. In fact, flow in the lumen apoplast is flow through leaky tubes, and is inadequately described by the Hagen-Poiseuille Law. Leaky tubes have a critical radius, below which (for a given pressure gradient) flow cannot occur. As a consequence of this, a wedge of xylem made up of vessels of different radii acts as a unit to concentrate dye tracers in a sump at its apex. Sumps may also be formed by evaporation of the water in the stream, especially at leaf margins. Investigations with the cryo-analytical scanning electron microscope of the natural ions of the transpiration stream reveal high concentrations of K, Cl, P and Ca in the stream in all the sizes of vessel and vein of sunflower leaves. These high concentrations appear to be produced, not by the mechanisms responsible for the formation of sumps of dyes, but by some other processes, probably occurring in the stem. The absence of sump formation by ions at the places where dyes form sumps is probably due to the more rapid penetration of the ions through the cell membranes. Reasons for the discrepancy between these measurements of salt concentrations in the stream and those obtained from sap expressed from leaves by pressure vessels are discussed. Implications of these facts for the design and interpretation of experiments with leaves are presented.

Transpiration Stream

1910 ◽  
Vol 50 (3) ◽  
pp. 237-238
Author(s):  
William Crocker
Keyword(s):  
Transpiration Stream
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