scholarly journals Long-Distance Water Transport in Aquatic Plants

1993 ◽  
Vol 103 (4) ◽  
pp. 1369-1375 ◽  
Author(s):  
O. Pedersen
Keyword(s):  
Water Transport ◽  
Aquatic Plants ◽  
Long Distance

scholarly journals Roman Water Transport: Pressure Lines

Water ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 28
Author(s):  
Paul M. Kessener
Keyword(s):  
Water Transport ◽  
Common Knowledge ◽  
Construction Materials ◽  
Minor Importance ◽  
Long Distance ◽  
Public And Private ◽  
Technical Problems ◽  
Pax Romana ◽  
And Function ◽  
Political Turmoil

In Roman times long distance water transport was realized by means of aqueducts. Water was conveyed in mortared open channels with a downward slope from spring to destination. Also wooden channels and clay pipelines were applied. The Aqua Appia, the oldest aqueduct of Rome, was constructed in the third Century BCE. During the Pax Romana (second Century CE), a time of little political turmoil, prosperity greatly increased, almost every town acquiring one or more aqueducts to meet the rising demand from the growth of population, the increasing number of public and private bath buildings, and the higher luxury level in general. Until today over 1600 aqueducts have been described, Gallia (France) alone counting more than 300. Whenever a valley was judged to be too wide or too deep to be crossed by a bridge, pressure lines known as ‘inverted siphons’ or simply ‘siphons’ were employed. These closed conduits transported water across a valley according the principle of communicating vessels. About 80 classical siphons are presently known with one out of twenty aqueducts being equipped with a siphon. After an introductory note about aqueducts in general, this report treats the ancient pressure conduit systems with the technical problems encountered in design and function, the techniques that the ancient engineers applied to cope with these problems, and the texts of the Roman author Vitruvius on the subject. Reviewers noted that the report is rather long, and it is. Yet to understand the difficulties that the engineers of those days encountered in view of the materials available for their siphons (stone, ceramics, lead), many a hydraulic aspect will be discussed. Aspects that for the modern hydraulic engineer may be common knowledge and of minor importance when constructing pressure lines, in view of modern construction materials. It was different in Vitruvius’s days.

scholarly journals Long-Distance Water Transport of Land Plants Using the Thermodynamic Sorption Principle

2019 ◽  
Author(s):  
Karlheinz Hahn
Keyword(s):  
Fluid Flow ◽  
Water Transport ◽  
Water Movement ◽  
Bulk Flow ◽  
Long Distance ◽  
Moisture Movement ◽  
Bulk Fluid ◽  
Basic Law ◽  
Vessel Elements ◽  
Cohesion Theory

In the case of vascular plants the process of water loss by leafs and water absorption by the root is well known. There is agreement on the passive nature of long-distance moisture movement in the dead cells of the xylem; however, controversy exists focusing on the long-distance water transport principle. Hales (1726) founded a view of bulk flow based on water suction after experiments with cut twigs. The previous doctrine of long-distance water transport within vessel elements and tracheid of the xylem of intact plants – the relevant cohesion theory in text books – was developed mainly by Boehm (1893), Renner (1911) and Dixon (1914) with plant artefacts.  Water movement according to this theory is based on an assumed hydrodynamic bulk fluid flow in xylem in continuous water columns (free of water vapour space), under tension, according to the law of Poiseuille (see e.g. Dixon 1914). Physically hydrodynamics is part of fluid mechanics, as a result Poiseuille’s law is usually valid only for hydrodynamic bulk flow in ideal capillaries (Sutera & Skalak, 1993). Besides the basic requirement for transport, according to cohesion theory, the existence of ideal capillaries is not compatible with either: “Because vessel elements and tracheid do not stand as ideal capillaries. …” (Bresinsky et al. 2008, translated from German). Unlike ideal capillaries, the walls of vessel elements and tracheid interact with the transported water.  These walls are able to function as a source or as a sink for the transported water because of interaction with the cell walls. With the interaction, vessel elements and tracheid, part of the xylem, can shrink and swell, unlike ideal capillaries. Because the xylem (in woody plants part of the wood) is inconsistent with the basic law of fluid flow, the equation of mass balance (Zimmermann et al. 2004) and cohesion theory are not strictly followed.Many plant physiologists view the cohesion theory as appropriate, however, this theory remains controver­sial, i.e. by Eisenhut (1988), Laschimke (1990) and Hahn (1993). Nultsch (1996) gives doubts referring to the present doctrine of plant water transport. Zimmermann et al. (2004) reject the cohesion theory and conclude: “... that the arguments of the proponents of the Cohesion Theory are completely misleading” (Zimmermann et al. 2004). Hence cohesion theory can be treated as inapplicable and the question arises: how does water transport in fact function?  In the following, it is gone into in more detail.  A sorption hypothesis of actual water transport, based on empirical fact, shall be addressed in this paper.

Embolism Repair and Long Distance Water Transport

2005 ◽  
pp. 375-399 ◽  
Author(s):  
Michael J. Clearwater ◽  
Guillermo Goldstein
Keyword(s):  
Water Transport ◽  
Long Distance
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