Transpirational pull is the main phenomenon driving the flow of water in the xylem tissues of large plants. Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... In vascular plants, xylem is one of the two types of transport tissue in plants, phloem being the other one. ... Divisions Green algae Chlorophyta Charophyta Land plants (embryophytes) Non-vascular plants (bryophytes) Marchantiophyta—liverworts Anthocerotophyta—hornworts Bryophyta—mosses Vascular plants (tracheophytes) †Rhyniophyta—rhyniophytes †Zosterophyllophyta—zosterophylls Lycopodiophyta—clubmosses †Trimerophytophyta—trimerophytes Pteridophyta—ferns and horsetails Seed plants (spermatophytes) †Pteridospermatophyta—seed ferns Pinophyta—conifers Cycadophyta—cycads Ginkgophyta—ginkgo Gnetophyta—gnetae Magnoliophyta—flowering plants...

Transpirational pull results ultimately from the evaporation of water from the surfaces of cells in the interior of the leaves. This evaporation causes the surface of the water to pull back into the pores of the cell wall. Inside the pores, the water forms a concave meniscus. The high surface tension of water pulls the concavity outwards, generating enough force to lift water as high as a hundred meters from ground level to a tree's highest branches. Transpirational pull only works because the vessels transporting the water are very small in diameter, otherwise cavitation would break the water column. Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell. Cells in culture, stained for keratin (red) and DNA (green). ... “Foliage” redirects here. ... A pore, in general, is some form of opening, usually very small. ... A cell wall is a fairly rigid layer surrounding a cell, located external to the cell membrane, that provides the cell with structural support, protection, and a filtering mechanism. ... A: Read the bottom of a concave meniscus. ... In physics, force is an influence that may cause an object to accelerate. ... The coniferous Coast Redwood, the tallest tree species on earth. ... This article or section does not cite any references or sources. ...

Until recently, the negative pressure (suction) of transpirational pull could only be measured indirectly, by applying external pressure with a Scholander bomb to counteract it. The name comes from the inventor, P.F. Scholander, and from its disconcerting tendency to explode in the experimenter's face. When the technology to perform direct measurements with a pressure probe was developed, there was initially some controversy about whether the classic theory was correct, because some workers were unable to demonstrate negative pressures. More recent measurements do tend to validate the classic theory, for the most part. Xylem transport is driven by a combination of transpirational pull from above and root pressure from below, which makes the interpretation of measurements more complicated. Root pressure is one of the phenomena used by vascular plants to move water into the leaves. ...

A common misconception is that water moves in xylem by capillary action—the movement of water along a small-diameter conduit (such as a capillary) as a result of surface tension in the meniscus at the leading surface of the moving water. Surface tension does play a critical role in water movement in xylem, as described above, but the relevant force acts at the surface site of evaporation within leaves, not within the xylem conduits. Water movement within the xylem conduits is driven by a pressure gradient created by such force, not by capillary action. Specifically, the evaporation and transpiration of water in the leaves causes water in the xylem to move from the roots, which have a higher water potential, up the stem of the plant that has a decreasing water potential along its length. Capillary action, capillarity, or capillary motion is the ability of a substance (the standard reference is to a tube in plants but can be seen readily with porous paper) to draw a substance up against gravity. ... This does not cite any references or sources. ...

Cohesion-tension theory

The cohesion-tension theory is a theory of intermolecular attraction commonly observed in the process of water travelling upwards (against the force of gravity) through the xylem of plants. The word theory has a number of distinct meanings in different fields of knowledge, depending on their methodologies and the context of discussion. ... Intermolecular attraction Intermolecular attraction is the strong forces of attraction of the molecules of iron make it hard to break. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... Gravity is a force of attraction that acts between bodies that have mass. ... In vascular plants, xylem is one of the two types of transport tissue in plants, phloem being the other one. ... Divisions Green algae Chlorophyta Charophyta Land plants (embryophytes) Non-vascular plants (bryophytes) Marchantiophyta—liverworts Anthocerotophyta—hornworts Bryophyta—mosses Vascular plants (tracheophytes) †Rhyniophyta—rhyniophytes †Zosterophyllophyta—zosterophylls Lycopodiophyta—clubmosses †Trimerophytophyta—trimerophytes Pteridophyta—ferns and horsetails Seed plants (spermatophytes) †Pteridospermatophyta—seed ferns Pinophyta—conifers Cycadophyta—cycads Ginkgophyta—ginkgo Gnetophyta—gnetae Magnoliophyta—flowering plants...

Water is a polar molecule due to the high electronegativity of the oxygen atom, which is an uncommon molecular configuration whereby the oxygen atom has two lone pairs of electrons. When two water molecules approach one other they form a hydrogen bond. The negatively charged oxygen atom of one water molecule forms a hydrogen bond with a positively charged hydrogen atom in another water molecule. This attractive force has several manifestations. Firstly, it causes water to be liquid at room temperature, while other lightweight molecules would be in a gaseous phase. Secondly, it (along with other intermolecular forces) is one of the principal factors responsible for the occurrence of surface tension in liquid water. This attractive force between molecules allows plants to draw water from the root (via osmosis) and then through the xylem (via capillary action) to the leaf where photosynthesis converts water and carbon dioxide into glucose. A commonly-used example of a polar compound is water (H2O). ... Electronegativity is a measure of the ability of an atom or molecule to attract electrons in the context of a chemical bond. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ... Properties In chemistry and physics, an atom (Greek ἄτομος or átomos meaning indivisible) is the smallest particle still characterizing a chemical element. ... A lone pair is an electron pair without bonding or sharing with other atoms. ... e- redirects here. ... An example of a quadruple hydrogen bond between a self-assembled dimer complex reported by Meijer and coworkers. ... A liquid will usually assume the shape of its container A liquid is one of the main states of matter. ... Room temperature describes a certain temperature within enclosed space that is uses for various purposes by human beings. ... This article does not cite any references or sources. ... In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i. ... This article or section is in need of attention from an expert on the subject. ... In physics, surface tension is an effect within the surface layer of a liquid that causes that layer to behave as an elastic sheet. ... Osmosis is the net movement of water across a partially permeable membrane from a region of high solvent potential to an area of low solvent potential, up a solute concentration gradient. ... In vascular plants, xylem is one of the two types of transport tissue in plants, phloem being the other one. ... Capillary action, capillarity, or capillary motion is the ability of a substance (the standard reference is to a tube in plants but can be seen readily with porous paper) to draw a substance up against gravity. ... The leaf is the primary site of photosynthesis in plants. ... In order to meet Wikipedias quality standards, this article requires cleanup. ... Glucose (Glc), a monosaccharide (or simple sugar), is the most important carbohydrate in biology. ...

Water is constantly lost by transpiration in the leaf. When one water molecule is lost another is pulled along. Transpiration pull, utilizing capillary action and the inherent surface tension of water, is the primary mechanism of water movement in plants. However, it is not the only mechanism involved. Any use of water in leaves produces forces that causes water to move into them. Capillary action, capillarity, or capillary motion is the ability of a substance (the standard reference is to a tube in plants but can be seen readily with porous paper) to draw a substance up against gravity. ...

See also

• secondary xylem
• secondary growth
• soil plant atmosphere continuum
• suction
• vascular tissue
• vascular bundle
• xylem

Secondary xylem is formed by a vascular cambium. ... In vascular plants, secondary growth or, perhaps more accurately, secondary thickening is the result of the activity of the vascular cambium. ... The Soil-Plant-Atmosphere Continuum (SPAC) is the pathway for water moving from soil through the plant to the atmosphere. ... Suction is the creation of a partial vacuum, or region of low pressure. ... Cross section of celery stalk, showing vascular bundles, which include both phloem and xylem. ... Cross section of celery stalk, showing vascular bundles, which include both phloem and xylem. ... In vascular plants, xylem is one of the two types of transport tissue in plants, phloem being the other one. ...

References

• The comprehensive textbook Biology, 6th ed., by Neil A. Campbell and Jane B. Reece, published by Benjamin Cummings, has been used as a source.

• C. WEI, E. STEUDLE, M. T. TYREE3 & P. M. LINTILHAC, The essentials of direct xylem pressure measurement, Plant, Cell and Environment (2001) 24, 549?555, is the main source used for the paragraph on recent research.

• N. Michele Holbrook, Michael J. Burns, and Christopher B. Field, Negative Xylem Pressures in Plants: A Test of the Balancing Pressure Technique, Science 270 (1995), 1193, is the first published independent test showing the Scholander bomb actually does measure the tension in the xylem.

• Pockman, W.T., J.S. Sperry and J.W. O'Leary. Sustained and significant negative water pressure in xylem. Nature 378 (1995) 715-716, , is the second published independent test showing the Scholander bomb actually does measure the tension in the xylem.

• Xylem Structure and the Ascent of Sap, 2nd ed. by Melvin T. Tyree & Martin H. Zimmermann (ISBN 3-540-43354-6) recent update of the classic book on xylem transport by the late Martin Zimmermann

Science is the journal of the American Association for the Advancement of Science (AAAS). ... Nature is one of the most prominent scientific journals, first published on 4 November 1869. ...

External links

• Research reported by E. Steudle

• Research reported by N. Holbrook

• Research reported by M. Tyree

• Research reported by J. Sperry