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Topic: Xylem vessels

	Xylem - Wikipedia, the free encyclopedia
		The xylem is the principal water-conducting tissue of vascular plants.
		However, the occurrence of vessel elements is not restricted to angiosperms, and they are absent in some archaic or "basal" lineages of the angiosperms: (e.g., Amborellaceae, Tetracentraceae, Trochodendraceae, and Winteraceae), and their secondary xylem is described by Arthur Cronquist as "primitively vesselless".
		Whether the absence of vessels in basal angiosperms is a primitive condition is contested, the alternative hypothesis being that vessel elements originated in a precursor to the angiosperms and were subsquently lost.
	en.wikipedia.org /wiki/Xylem (841 words)

	Root pressure - Wikipedia, the free encyclopedia
		Root pressure occurs in the xylem of some vascular plants when the soil moisture level is high either at night or when transpiration is low during the day.
		Root pressure is caused by this accumulation of water in the xylem pushing on the rigid cells.
		Sugar maple accumulates high concentrations of sugars in its xylem early in the spring, which is the source of maple sugar.
	en.wikipedia.org /wiki/Root_pressure (772 words)

	Xylem (Site not responding. Last check: 2007-10-29)
		Xylem is a complex tissue composed of xylem vessels, xylem tracheids, xylem fibres and xylem parenchyma.
		The secondary walls of vessels are impregnated with lignin and are thickened unevenly.
		Xylem fibres are sometimes separated by thin cross walls and the walls of xylem parenchyma are sometimes thicker than those of normal parenchyma.
	www.botany.uwc.ac.za /SCI_ED/grade10/plant_tissues/xylem.htm (199 words)

	Leucostoma Anatomy
		The mycelium was intracellular in the xylem vessels and pith.
		The walls of xylem vessels located up to 2 cm beyond the margin of the cankers exhibited a brown discoloration, primarily in the vessels near the pith but extending throughout the wood with increased proximity to the canker margin (Figs.
		Xylem colonization was ahead of that in bark by 1 cm proximal to the visible canker margin but equal to that in bark distally.
	www.caf.wvu.edu /bark/leucostoma.htm (6898 words)

	Water movement through a plant
		Xylem vessels are long, narrow, hollow tubes containing no living material and impregnated with bands or spirals of lignin.
		The narrow diameters of the xylem vessels increase the capillarity forces, however once again, this only makes a small contribution to water's upward movement.
		Xylem vessels* in stem LS Looking at leaf structure provides the clues to what is the main force involved in maintaining a continuous flow of water from root to leaf through the xylem.
	www.microscopy-uk.org.uk /mag/artmar00/watermvt4.html (272 words)

	[No title]
		It is important to recognize that the mature xylem and its contents must be considered as apoplast in the root, stem or leaf tissue; whereever the xylem vascular tissues are present.
		Xylem Transport: Movement of solutes within the xylem is facilitated primarily by mass flow of water in the water transport system of the plant, in other words convective forces.
		However, it is important to remember that the hydraulic conductance of the xylem is a function of the radius of the xylem elements, trachieds or vessels.
	www.msu.edu /course/hrt/853/NUTLEC8.html (2444 words)

	BiologyMad A-Level Biology
		In dicot plants (the broad-leafed plants), the vascular tissue is arranged in vascular bundles, with phloem on the outside and xylem on the inside.
		The very strong lignin walls of the xylem vessels stops them collapsing under the suction pressure, but in fact the xylem vessels (and even whole stems and trunks) do shrink slightly during the day when transpiration is maximum.
		Since the phloem vessels are outside the xylem vessels, they can be selectively removed by cutting a ring in a stem just deep enough to cut the phloem but not the xylem.
	www.biologymad.com /PlantTransport/PlantTransport.htm (2342 words)

	Botany online: Supporting Tissues - Vascular Tissues - Xylem
		Wood vessels are the chief water-conducting elements of angiosperms.
		During ontogenesis the wood vessels increase strongly in width.They are usually round in cross-section and have a larger diameter than the tracheids, a feature that enhances their capacity for water-conduct.
		Vessels are marked by characteristically structured secondary wall coatings (lignin) at the inner surface of the primary walls.
	www.biologie.uni-hamburg.de /b-online/e06/06b.htm (856 words)

	Harvard Forest Symposium Abstract Submission
		Air seeding threshold (Pa) of xylem vessels from current year growth rings were measured along the vertical axis of mature sugar maple trees (Acer saccharum Marsh.), with sampling points in primary leaf veins, petioles, 1, 3, and 7-year-old branches, large branches, the trunk and roots.
		Mean xylem vessel diameter increased basipetally, with the widest vessels occurring in the trunk and roots.
		The difference in Pa between primary and secondary xylem was attributed the greater area of primary cell wall (pit membrane) exposed in primary xylem conduits with helical or annular thickening (Fig3).
	harvardforest.fas.harvard.edu /asp/hf/showsymposium.html?id=2 (317 words)

	Root Xylem Embolisms and Refilling. Relation to Water Potentials of Soil, Roots, and Leaves, and Osmotic Potentials of ...
		The proportion of embolized, LMX vessels peaked in the
		The face of the block passes through an embolized LMX vessel that is refilling (as indicated by the convex shape of the frozen drops).
		Some pits in the lateral wall of this vessel (toward the right of the micrograph) are not yet flooded, but drops of xylem sap were entering the vessel lumen through pits closer to the left of the micrograph (arrowheads).
	www.plantphysiol.org /cgi/content/full/119/3/1001 (5017 words)

	module 3 notes (Site not responding. Last check: 2007-10-29)
		The substances that are transported in the phloem and the xylem
		The xylem vessels are found in a star shaped formation in the centre of the stele, with phloem vessels found in between the points of the stars.
		The evaporation creates a WP gradient and the properties of water and the xylem vessels allow this pressure to be transmitted all the way to the roots even in the tallest trees.
	www.mrothery.co.uk /plants/planttransportnotes.htm (1446 words)

	Vasular wilt diseases (Site not responding. Last check: 2007-10-29)
		Vascular wilt diseases are caused by pathogenic fungi or bacteria that enter the water-conducting xylem vessels of a plant, then proliferate within the vessels, causing water blockage.
		For example, the blockage of the xylem vessels is not necessarily caused by the pathogens themselves but often by the host reactions to invasion - the production of gel-like materials which serve as potential barriers to spread of the pathogens in the vessels.
		Panama disease is a classic vascular wilt disease, in which a fungus, Fusarium oxysporum, gains entry to the water-conducting xylem vessels, then produces spores that are carried upwards in the water stream.The upwards spread is blocked temporarily when the spores lodge on the perforated vessel end walls that occur at intervals up the plant.
	helios.bto.ed.ac.uk /bto/microbes/panama.htm (1075 words)

	Anatomy of the vessel network within and between tree rings of Fraxinus lanuginosa (Oleaceae) -- Kitin et al. 91 (6): ... (Site not responding. Last check: 2007-10-29)
		Identical earlywood vessels are indicated by the same number, and identical vessel multiples in the latewood are indicated by the same letter.
		The vessel network was reconstructed by analysis of a series of transverse sections, some of which are shown in Fig.
		vessel is mediated by the concentration of ions in the xylem
	www.amjbot.org /cgi/content/full/91/6/779 (5526 words)

	Cryo-Scanning Electron Microscopy Observations of Vessel Content during Transpiration in Walnut Petioles. Facts or ...
		Vessels were either entirely water filled (vessels on the left side of the picture) or one-half-filled with sap (right side).
		The water stress was induced in the xylem by the transpiration pull for leaves collected in the field (squares) or by exposing excised petioles to different centrifugal forces (circles).
		A VC is a graph of the degree of xylem embolism versus the xylem water potential that induced the embolism.
	www.plantphysiol.org /cgi/content/full/124/3/1191 (7125 words)

	Transcription switches for protoxylem and metaxylem vessel formation -- Kubo et al. 19 (16): 1855 -- Genes and ...
		Xylem vessels, a conductive component of the vascular tissues
		of the primary xylem tissue that differentiates from the procambium
		xylem vessel elements were actively forming (6 d after induction).
	www.genesdev.org /cgi/content/full/19/16/1855 (3445 words)

	Bordered Pit Structure and Vessel Wall Surface Properties. Implications for Embolism Repair -- Zwieniecki and Holbrook ...
		The primary function of the xylem is to provide a pathway for water movement through the plant.
		Each frame shows the superposition of the vessel with water droplet in place over the same image after the droplet had been retracted into the capillary tube such that the outline of the vessel wall was more distinct.
		Zimmermann MH (1983) Xylem Structure and the Ascent of Sap.
	www.plantphysiol.org /cgi/content/full/123/3/1015 (2724 words)

	Hydraulic vulnerability, vessel refilling, and seasonal courses of stem water potential of Sorbus aucuparia L. and ...
		), xylem sap in the vessels of transpiring
		Xylem dysfunction during winter and recovery of hydraulic conductivity in diffuse-porous and ring-porous trees.
		Drought tolerance, xylem sap abscisic acid and stomatal conductance during soil drying: a comparison of young plants of four temperate deciduous angiosperms.
	jxb.oxfordjournals.org /cgi/content/full/52/360/1527 (4663 words)

	[No title]
		Capillarity or adhesion is responsible for some water creeping up the xylem vessels simply because they are very narrow and so the water molecules stick to the walls of the xylem cells.
		Transpiration pull is caused by the surroundings which cause water molecules to transpire from the leaves of the plant.
		This causes water to leave the xylem and enter the leaves by osmosis and so more water enters the xylem to replace that which is lost.
	www.trinity.nottingham.sch.uk /biology/transport.doc (447 words)

	Functional Imaging of Plants: A Nuclear Magnetic Resonance Study of a Cucumber Plant -- Scheenen et al. 82 (1): 481 -- ...
		The amount of flowing water can be recalculated in the cross-sectional area of flow for every pixel, assuming that a vessel is homogeneous along the direction of the plant stem over the thickness of the slice (3 mm).
		A non-invasive measurement of phloem and xylem water flow in castor bean seedlings by nuclear magnetic resonance microimaging.
		Milburn, J. Sap ascent in vascular plants: challengers to the cohesion theory ignore the significance of immature xylem and the recycling of Munch water.
	www.biophysj.org /cgi/content/full/82/1/481 (6439 words)

	Seasonal conductivity and embolism in the roots and stems of two clonal ring-porous trees, Sassafras albidum ... (Site not responding. Last check: 2007-10-29)
		Ewers, F. 1985 Xylem structure and water conduction in conifer trees, dicot trees, and lianas.
		Gartner, B. 1995 Patterns of xylem variation within a tree and their hydraulic and mechanical consequences.
		The vulnerability to freezing-induced xylem cavitation of Larrea tridentata (Zygophyllaceae) in the Chihuahuan desert
	www.amjbot.org /cgi/content/full/88/2/206 (4839 words)

	Bundle sheath cells of small veins in maize leaves are the location of uptake from the xylem -- Keunecke et al. 52 ...
		of ions from the xylem vessels to the symplast of leaves.
		The symbols in (A) and (B) denote the borders between cell (or vessel) and cell as defined in Fig.
		Wegner LH, Raschke K. Ion channels in xylem parenchyma cells from barley roots: a procedure to isolate protoplasts from this tissue and a patch-clamp exploration of salt passageways into xylem vessels.
	jxb.oxfordjournals.org /cgi/content/full/52/357/709 (2982 words)

	The following represent questions from Chapter 36
		A) Weak bonding between water molecules and the walls of xylem vessels or tracheids helps support the columns of water in the xylem.
		C) Water molecules are transpired from the cells of the leaves, and replaced by water molecules in the xylem pulled up from the roots due to the cohesion of water molecules.
		E) In the morning, sap in the xylem begins to move first in the twigs of the upper portion of the tree, and later in the lower trunk.
	www.mvcc.edu /~rthomas/Bi101/Prac_Ques_Ch36.cfm (1458 words)

	Control of Cellulose Synthase Complex Localization in Developing Xylem -- Gardiner et al. 15 (8): 1740 -- THE PLANT CELL
		Kobayashi, H., Fukuda, H., and Shibaoka, H. Reorganization of actin filaments associated with the differentiation of tracheary elements in Zinnia mesophyll cells.
		Turner, S.R., and Somerville, C.R. Collapsed xylem phenotype of Arabidopsis identifies mutants deficient in cellulose deposition in the secondary cell wall.
		The Xylem and Phloem Transcriptomes from Secondary Tissues of the Arabidopsis Root-Hypocotyl
	www.plantcell.org /cgi/content/full/15/8/1740 (4819 words)

	The structure of xylem vessels in grapevine (Vitaceae) and a possible passive mechanism for the systemic spread of ...
		The structure of xylem vessels in grapevine (Vitaceae) and a possible passive mechanism for the systemic spread of bacterial disease -- Thorne et al.
		The structure of xylem vessels in grapevine (Vitaceae) and a possible passive mechanism for the systemic spread of bacterial disease
		vessels from the petiole into the veins in leaves of both varieties.
	www.amjbot.org /cgi/content/abstract/93/4/497 (316 words)

	Wilt diseases
		C. Some of the current year's xylem on affected branches becomes discolored, though it may be covered by newer, non-discolored xylem.
		B. Once established in the vessels, small spores are produced which travel freely in the sap column.
		Hyphae and spores accumulate at the xylem end-walls.
	www.csupomona.edu /~froth/hor427/treewilts.html (1286 words)

	BBC - GCSE Bitesize - Biology \| Green plants \| The transport system
		The cells of these vessels are modified to make them suited to performing their special functions.
		The two types of vessel are always found together, but they occupy slightly different locations in the root and the stem:
		Water is taken up the plant from the roots to the leaves (for photosynthesis and transpiration) - in xylem vessels.
	www.bbc.co.uk /schools/gcsebitesize/biology/greenplantsasorganisms/1watertransportrev3.shtml (531 words)

	Movement of rice yellow mottle virus between xylem cells through pit membranes -- Opalka et al. 95 (6): 3323 -- ...
		In this study, we observed the accumulation of large amounts of RYMV in xylem parenchyma cells and vessels.
		in xylem vessels to allow their spread throughout the plant.
		between a vessel and a living parenchyma cell remains to be examined.
	www.pnas.org /cgi/content/full/95/6/3323 (3157 words)

	2002F_lect7_stem2 (Site not responding. Last check: 2007-10-29)
		Heartwood = made of old xylem that are no longer conductive of water, but are filled with resins etc.
		Sapwood = made of xylem that are conductive of water (i.e., xylem whose tracheary elements are not cavitated).
		On average, conductive tubes are much narrower for gymnosperms than angiosperms, and thus gymnosperms have slower rate of flow for both water and sugar sap.
	www.clas.ufl.edu /users/kitajima/BOT2010/2002F_lect7_stem2.html (465 words)

	Term Test 2 (11-Mar-03)
		Secondary xylem vessels with simple perforations found only in the roots.
		All seven genera are flowering plants, but genus 1 has wood resembling that of gymnosperms in that it consists exclusively of tracheids and fibers; vessels are completely lacking.
		Where vessels are present they vary with respect to perforation plate structure (scalariform - thought to be more primitive; e.g.
	www.botany.utoronto.ca /courses/Bot300/300TermTest2.html (888 words)

	Cooksonia (2)
		The presence of xylem vessels with annular or spiral-shaped thickenings at the walls counts as characteristic for higher plants.
		D. Edwards (1992) was the first one to publish photos of xylem vessels of Cooksonia (Photo with permission of Nature Publishing Group).
		Some of the axes show a fl line, probably pointing at the presence of xylem vessels.
	www.xs4all.nl /~steurh/engcook/ecooks2.html (882 words)

	Chapter 32 (Site not responding. Last check: 2007-10-29)
		Figure 32.2B: Routes of water andsolutes from soil to root xylem
		as water enters xylem it pushes the xylem sap upward ahead of it
		which means movement of phloem sap is not unidirectional as in the upward movement of xylem sap
	www.nv.cc.va.us /home/klargen/104lecturech32.htm (1021 words)

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