phloem

/floh"em/, n.
the part of a vascular bundle consisting of sieve tubes, companion cells, parenchyma, and fibers and forming the food-conducting tissue of a plant.
[ < G (1858), irreg. < Gk phló(os) bark (var. of PHLOIÓS) + -ema deverbal n. ending]

* * *

or bast

Plant tissues that conduct foods made in the leaves to all other parts of the plant.

Phloem is composed of several types of specialized cells, including sieve-tube cells and phloem fibers. Sieve tubes (columns of sieve-tube cells), which have perforated areas in their walls, provide the main channels in which food substances travel. Phloem fibers are long, flexible cells that make up the soft fibers used commercially (e.g., flax and hemp).

* * *

▪ plant tissue
also called  bast 
 tissues in plants that conduct foods made in the leaves to all other parts of the plant. Phloem is composed of various specialized cells called sieve tubes (sieve tube), companion cells, phloem fibres, and phloem parenchyma cells. Primary phloem is formed by the apical meristems (zones of new cell production) of root and shoot tips; it may be either protophloem, the cells of which are matured before elongation (during growth) of the area in which it lies, or metaphloem, the cells of which mature after elongation. Sieve tubes of protophloem are unable to stretch with the elongating tissues and are torn and destroyed as the plant ages. The other cell types in the phloem may be converted to fibres. The later maturing metaphloem is not destroyed and may function during the rest of the plant's life in plants such as palms but is replaced by secondary phloem in plants that have a cambium.

      Sieve tubes, which are columns of sieve-tube cells having perforated, sievelike areas in their lateral or end walls, provide the channels in which food substances travel. Phloem parenchyma cells, called transfer cells and border parenchyma cells, are located near the finest branches and terminations of sieve tubes in leaf veinlets, where they also function in the transport of foods. Phloem fibres are flexible long cells that make up the soft fibres (e.g., flax and hemp) of commerce.

* * *


Universalium. 2010.

Look at other dictionaries:

  • phloem — 1875, from Ger. phloëm (1858), from Gk. phloos, phloios bark + passive suffix ema …   Etymology dictionary

  • Phloem — Phlo [ e]m, n. [Gr. ? bark.] (Bot.) That portion of fibrovascular bundles which corresponds to the inner bark; the liber tissue; distinguished from xylem. [1913 Webster] …   The Collaborative International Dictionary of English

  • Phloëm — (griech.), s. Leitbündel, S. 390 …   Meyers Großes Konversations-Lexikon

  • Phloem — Phloēm (grch.), in der Botanik die Gewebepartien, in denen die eiweißleitenden Elemente (Siebröhren etc.) enthalten sind …   Kleines Konversations-Lexikon

  • Phloem — Phloem, Bastteil, Siebteil, dem Transport der Assimilate und einiger organischer Nährstoffe dienendes Leitgewebe in Cormophyten. Zu ihm gehören als Leitungselemente bei Pteridophyten (Farnpflanzen) und Gymnospermen (Nacktsamern) ⇒ Siebzellen, bei …   Deutsch wörterbuch der biologie

  • phloem — ► NOUN Botany ▪ the tissue in plants which conducts food materials downwards from the leaves. ORIGIN from Greek phloos bark …   English terms dictionary

  • phloem — [flō′em΄] n. [Ger < Gr phloos, bark, akin to phloiein, to swell: for IE base see PHLEBO ] the vascular tissue in vascular plants, that conducts and distributes sugars and other dissolved foods from the places where the food is produced to the… …   English World dictionary

  • Phloem — Gefärbter Querschnitt durch eine Sprossachse einer Einkeimblättrigen Pflanze. Das Phloem ist mit einem Pfeil markiert und kaum gefärbt. Oben befindet sich das Xylem. Das Phloem ([flo e:m], von gr. φλοῦς < φλό ος phlóos = Bast, Rinde) oder der… …   Deutsch Wikipedia

  • Phloem — Cross section of a flax plant stem: 1. Pith, 2. Protoxylem, 3. Xylem I, 4. Phloem I, 5. Sclerenchyma (bast fibre), 6. Cortex, 7. Epidermis In vascular plants, phloem is the living tissue that carries organic …   Wikipedia

  • Phloem — Phlo|em 〈n. 11; bei Pflanzen〉 Siebteil der Leitbündel; Sy Leptom [zu grch. phloios „Bast“] * * * Phlo|em, das; s, e [zu griech. phlóos = Bast, Rinde] (Bot.): Teil des Leitbündels, der zum Transport der in den Blättern gebildeten Stoffe innerhalb… …   Universal-Lexikon

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.