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Topic: Phloem

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In the News (Sat 19 Apr 14)

 Phloem - Wikipedia, the free encyclopedia
The movement in phloem is bidirectional, whereas, in xylem cells, it is unidirectional (upward).
Phloem of pine trees has been used in Finland as a substitute food in times of famine, and even in good years in the northeast, where supplies of phloem from earlier years helped stave off starvation somewhat in the great famine of the 1860s.
Phloem is dried and milled to flour (pettu in Finnish) and mixed with rye to form a hard dark bread.
en.wikipedia.org /wiki/Phloem   (869 words)

Phloem tissue is usually found close to the other transport tissue in plants, xylem, which transports water and minerals.
Phloem is composed of sieve elements and their associated companion cells, together with some sclerenchyma and parenchyma cell types.
Phloem is usually found in association with xylem, the water-conducting tissue, but unlike the latter it is a living tissue.
www.tiscali.co.uk /reference/encyclopaedia/hutchinson/m0007061.html   (432 words)

 Index Phloem
Phloem and xylem derive from a common precursor: the procambium (for primary tissues) and the cambium (for secondary tissues).
In the phloem, enucleate sieve tubes are associated with companion cells and phloem parenchyma cells (Oparka and Turgeon, 1999).
In addition to this pivotal role in plant life, the phloem reaches all the plant organs and is therefore a privileged way for the propagation of phytopathogens, such as viruses, nematodes, fungi or phytoplasmas.
www-biocel.versailles.inra.fr /phloem/Background.html   (610 words)

 Steve's place - Phloem
In deciduous trees, sugars are moved from storage in the roots and trunk to the buds during spring, and from the photosynthesising shoot and leaves to the roots in summer.
Phloem transports photosynthate from sink to source in the same way as xylem transfers water from sources (soil) to sinks (leaves); and that arteries transfer oxygen from sources (lungs) to sinks (respiring cells); and that veins transfer sugars from sources (ileum) to sinks (liver).
The rate of phloem loading is controlled by the pressure in the sieve tubes: cutting the phloem (which releases the pressure) increases the rate of loading.
www.steve.gb.com /science/phloem.html   (2015 words)

 G7254 Elm Phloem Necrosis, MU Extension
Phloem necrosis of American elm is a disease of unknown origin of many years standing, which is now widespread in the region of the central and lower Ohio River watershed.
Phloem necrosis is caused by a mycoplasma-like organism (formerly believed to be a virus infection), and is usually spread from diseased to healthy elms by an insect, a leaf hopper, Scaphoideus leuteolus (Van Duzee).
If the discoloration seems typical for phloem necrosis but the wintergreen odor is difficult to detect, secure a new sample from another part of the tree and confine it in the stoppered container for several hours in a warm place.
muextension.missouri.edu /xplor/agguides/pests/g07254.htm   (767 words)

 [No title]
The rate of phloem flow is estimated by monitoring the movement of the front of radio activity in the plant.
Phloem import: Phloem import is import for both supplying young growing tissues with mineral nutrients before the xylem have matured.
Phloem export/remobilization is influenced by: a) Ability of nutrients to be converted from an insoluble to a soluble form, or to be released from subcellular compartments (vacuoles).
www.msu.edu /course/hrt/853/NUTLEC9.html   (1958 words)

 Botany online: Supporting Tissues - Vascular Tissues - Phloem
The phloem is the principal food-conducting tissue of vascular plants.
Phloem elements may be of primary or secondary origin though the early primary phloem, the
Phloem elements of the roots are normally organized in a more progressive and thus more efficient way than their equivalents in the shoots.
www.biologie.uni-hamburg.de /b-online/e06/06d.htm   (758 words)

 ARS | Publication request: Phloem and Xylem in the Vascular Sutures of the Soybean Pod
The xylem and phloem of the pod was investigated as a preliminary to the understanding of water and nutrient movement in the deposition and mobilization of storage compounds destined to be utilized by the developing seed.
Phloem is generally external to xylem and the presence of internal phloem is a rare occurrence in plants.
The phloem consists of sieve elements and adjoining companion cells and the xylem consists of tracheary elements.
www.ars.usda.gov /research/publications/publications.htm?SEQ_NO_115=107405&pf=1   (369 words)

 MSN Encarta - Search Results - Phloem
Phloem, in higher plants, vascular tissue that conducts sugars and other synthesized food materials from the regions of manufacture in the plant to...
The phloem, or food-conducting tissue, consists of cells that are living at maturity.
The principal cells of phloem, the sieve elements, are so...
ca.encarta.msn.com /Phloem.html   (99 words)

 Translocation of Food
Translocation through the phloem is dependent on metabolic activity of the phloem cells (in contrast to transport in the xylem).
Finally, relatively pure water is left in the phloem, and this leaves by osmosis and/or is drawn back into nearby xylem vessels by the suction of transpiration-pull.
The osmotic pressure of the fluid in the phloem of the leaves must be greater than that in the phloem of the food-receiving organs such as the roots and fruits.
users.rcn.com /jkimball.ma.ultranet/BiologyPages/P/Phloem.html   (815 words)

 Index Phloem
Events occurring in the phloem tissue are key to understand a range of developmental and physiological processes in vascular plants.
While molecular information on phloem genes has emerged in the past decade, a unified picture of the basic mechanisms involved in phloem differentiation and function is still lacking.
In the phloem of celery, major classes of mRNAs predominantly found encoded proteins related to structure, metal homeostasis or distribution, stress responses and degradation or turnover of proteins [4], that were further confirmed for phloem protein PP2 in other species [9].
www-biocel.versailles.inra.fr /phloem/poitiers-abst-Dinant.html   (942 words)

 Tuberization in Potato Involves a Switch from Apoplastic to Symplastic Phloem Unloading -- Viola et al. 13 (2): 385 -- ...
transport phloem of the stolon and the unloading phloem of the
The induction of symplastic phloem unloading in tuberizing stolons
Oparka, K.J. (1986) Phloem unloading in the potato tuber.
www.plantcell.org /cgi/content/full/13/2/385   (6861 words)

 Ecology: Nitrogen Budgets Of Phloem-Feeding Bark Beetles With And Without Symbiotic Fungi - Statistical Data Included
Bark beetles face a particularly severe challenge because the phloem that they consume is very low in nitrogen and phosphorus relative to their requirements.
Spatial variation in phloem N was mostly at the level of trees within sites (a scale of meters) while P mostly varied among sites (a scale of kilometers).
Prior to infestation by beetles, phloem nutrient concentrations were very uniform within trees and very low relative to that of the bark beetles (N and P concentrations of D. frontalis adults were 28 and 8 times greater, respectively).
www.findarticles.com /p/articles/mi_m2120/is_8_81/ai_65197825   (1066 words)

 FRST 200 - Phloem Transport   (Site not responding. Last check: 2007-10-21)
Phloem sap can be collected from the mouth-parts (stylets) of severed aphids.
Because phloem sap is freely exuded from these severed stylets, we know that it is under pressure.
It decreases the solute potential of the water in the phloem and, as a consequence, more water (from the xylem and other adjacent cells) enters the phloem by osmosis.
courses.forestry.ubc.ca /frst200/lectures/Phloem.htm   (334 words)

 Translocation in the Phloem   (Site not responding. Last check: 2007-10-21)
Phloem transport moves solutes from a source (more solutes then required for metabolism) to a sink, including a storage organ to an actively growing organ.
Phloem usually is located outside of the xylem in both primary and secondary vascular systems 
Solution movement in the phloem is based on the pressure gradient and not the water potential gradient because it is a bulk flow process
www.hort.purdue.edu /hort/courses/HORT301/MikesLectures/TranslPhloem.html   (1392 words)

 Search Results for phloem - Encyclopædia Britannica
Phloem is composed of various specialized cells called sieve tubes, companion cells, phloem fibres, and phloem...
In the leaf, transpiration, the evaporation of water and taking in of carbon dioxide for photosynthesis, is effected through pores called stomata, which are regulated by valve cells called guard...
In the secondary growth of the root, cell division in the primary xylem produces a cambium, which abuts the pericycle over the protoxylem ridges and passes between the phloem strands and the xylem in...
www.britannica.com /search?query=phloem&submit=Find&source=MWTAB   (368 words)

 Phloem - Phloem-specific homeobox gene   (Site not responding. Last check: 2007-10-21)
Nymph of whitebanded leafhopper, vector of elm phloem necrosis.
Its conducting cells are known as sieve elements, but phloem may also include companion As a vascular tissue, phloem is spatially associated with xylem,
phloem specific homeobox The vascular system is composed of two kinds of conducting We reported the first isolation of an immature phloem-specific gene,
phloem.siteslinks.com   (182 words)

 IngentaConnect How nutritionally imbalanced is phloem sap for aphids?   (Site not responding. Last check: 2007-10-21)
Phloem sap data from severed stylets of two aphid species, Rhopalosiphum padi (L.) (Homoptera: Aphididae) feeding on wheat, and Uroleucon sonchi (L.) (Homoptera: Aphididae) feeding on Sonchus oleraceus (L.), together with published information on phloem sap compositions from other plant species were used.
However, methionine and leucine in phloem sap are in general low in these comparisons, suggesting a higher dependence on the symbiont for synthesis of these amino acids.
Concentrations of several essential amino acids in phloem from different plant species seem to vary together, suggesting that levels of symbiont provisioning of different amino acids are adjusted in parallel.
www.ingentaconnect.com /content/klu/ento/1999/00000091/00000001/00207746   (409 words)

 Phloem Transport
Transport of photosynthate occurs mainly in the phloem
Phloem sap in most plants is very high in sucrose-the main translocated photosynthate
Mechanism of phloem translocation: pressure-flow hypothesis of Ernst Munch (1930)
www.esf.edu /efb/course/EFB530/lectures/phloem.htm   (650 words)

 An in vivo Experimental System to Study Sugar Phloem Unloading in Ripening Grape Berries During Water Deficiency Stress ...
that the sugar unloaded from the phloem is accumulated in the
Thereafter, the sugar efflux represents the sugar phloem unloading of the grape berry.
Phloem unloading of C and N assimilates in developing seeds.
aob.oxfordjournals.org /cgi/content/full/92/4/523   (3352 words)

 The evolution of minor vein phloem and phloem loading -- Turgeon et al. 88 (8): 1331 -- American Journal of Botany
Phloem parenchyma cells lie between the intermediary cell-sieve element complexes and the tracheary elements.
Wherever possible, genera for which phloem anatomy is known were coded directly in the matrix, but for some representatives there was no equivalent genus in the molecular matrix.
All taxa scored as missing for the phloem loading character were automatically pruned from the consensus tree, producing a tree topology that is a fully congruent subset of the topology with all taxa.
www.amjbot.org /cgi/content/full/88/8/1331   (4602 words)

Phloem differentiation is hard to follow because the
However, careful inspection leads to the conclusion that the tissue immediately opposite the xylem arose from the same shaft of cells (Procambium) as the xylem.
Thus, the Phloem can be located between the Fibers and the Xylem.
www.biologie.uni-hamburg.de /b-online/library/webb/BOT311/Phloem/Phloem-1.htm   (257 words)

 Phloem Transport of Fructans in the Crassulacean Acid Metabolism Species Agave deserti -- Wang and Nobel 116 (2): 709 ...
19% in the phloem sap (fructose for 24% and Suc for 53%).
The fructans in the phloem sap of A.
Turgeon R (1991) Symplastic phloem loading and the sink-source transition in leaves: a model.
www.plantphysiol.org /cgi/content/full/116/2/709   (3833 words)

 Phloem   (Site not responding. Last check: 2007-10-21)
We will concentrate on phloem translocation in angiosperms - although you should know that process varies considerably among angiosperms and is quite different in most gymnosperms.
Excluded from phloem and not moved - nitrate, calcium, sulfur and iron.
Phloem - on outer side of both primary and secondary vascular tissues.
www.bio.mtu.edu /~mrgretz/bl4140_www/phloem.htm   (753 words)

 Phloem loading and unloading of Cowpea mosaic virus in Vigna unguiculata -- Silva et al. 83 (6): 1493 -- Journal of ...
Phloem loading and unloading of Cowpea mosaic virus in Vigna unguiculata -- Silva et al.
Kempers, R. and Van Bel, A. Symplasmic connections between sieve element and companion cell in the stem phloem of Vicia faba L. have a molecular exclusion limit of at least 10 kDa.
Murant, A. and Roberts, I. Virus-like particles in phloem tissue of chervil (Anthriscus cerefolium) infected with carrot red leaf virus.
vir.sgmjournals.org /cgi/content/full/83/6/1493   (5844 words)

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