Name: how phloem moves sugars in plants
Uploaded: 2026-08-26T08:21:05.159Z
Duration: 2 min 10 s
Channel: JoVE

K12 Standards

Florida Department of Education

High School

Life Science

SC.912.L.14

SC.912.L.14.7

Phloem and Sugar Transport

Photosynthese generiert
Zucker in Pflanzenbl&#xE4;ttern.
Der Zucker wird allerdings
oft in entfernten Teilen
der Pflanze ben&#xF6;tigt.
Die Translokation ist der
Prozess, der die Produkte
der Photosynthese an andere
Pflanzengeweben
verteilt.
Bl&#xE4;tter werden normalerweise
als Zuckerquellen bezeichnet,
welche die Standorte sind, die
mehr Zucker produzieren, als sie konsumieren.
Im Gegensatz dazu sind die Wurzeln,
St&#xE4;mme und Fr&#xFC;chte typischerweise
Konsumenten von Zucker,
die als Zuckersenken bezeichnet werden.
Der Transport von Zucker
zwischen den Quellen und den Senken
geschieht im
Pflanzengewebe genannt Phloem.
Bei Angiospermen besteht das
Phloem aus spezialisierten Zellen,
die Siebrohrelemente
genannt werden, die durchgehend
angeordnet sind, um lange Rohre zu erzeugen.
Begleiterzellen sind
entlang jedes
Siebrohrelements befindlich.
Zucker kann das Phloem
&#xFC;ber mehrere Routen erreichen.
Er kann durch den
extrazellul&#xE4;ren Raum und die
Zellw&#xE4;nde oder durch Poren wandern, die
das Zytoplasma direkt mit
benachbarten Zellen verbindet.
Sobald der Zucker die
Begleiterzellen erreicht,
laden die Saccharin-Wasserstoff-
Cotransporter ihn aktiv
in die
Siebrohrelemente.
Eine w&#xE4;ssrige L&#xF6;sung
genannt Phloemsaft,
die aus Zucker, Aminos&#xE4;uren,
Hormonen und Mineralien besteht,
flie&#xDF;t durch die
Siebrohrelemente.
Entsprechend der
Druckflusshypothese flie&#xDF;t
Wasser dem Zucker folgend in
das Phloem durch Osmose,
was den Druck
innerhalb des Phloems erh&#xF6;ht
und daher die
Phloemsaftbewegung vorantreibt.
Phloemsaft flie&#xDF;t dann zum
nahesten Senkengewebe, das
eine geringe Zuckerkonzentration aufweist.
Der Zucker diffundiert entweder
oder wird aktiv
aus dem Phloem heraus transportiert.
Wenn der Zucker abgeladen wird, folgt
das Wasser durch Osmose nach und entl&#xE4;sst
Druck innerhalb des Phloem.
Indem sie Translokation
durch den Phloem verwenden,
k&#xF6;nnen Pflanzen die Ressourcen
an die Gewebe verteilen,
in denen sie zu einem bestimmten
Zeitpunkt oder Saison ben&#xF6;tigt werden.

Heo JO, Roszak P, Furuta KM, Helariutta Y. Phloem-Entwicklung: aktuelles Wissen und Zukunftsperspektiven. Am J Bot. September 2014; 101(9):1393-402. [<a href="https://www.ncbi.nlm.nih.gov/pubmed/25253700" target="_blank">Quelle</a>]

Liesche J, Patrick J. Ein Update zum Phloemtransport: ein einfacher Massengutfluss unter komplexer Regulierung. F1000Res. 2017 Dez 6;6:2096. [<a href="https://www.ncbi.nlm.nih.gov/pubmed/29259777" target="_blank">Quelle</a>]

phloem und zuckertransport

Wie viele andere Lebewesen besitzen Pflanzen Gewebe, die auf bestimmte Pflanzenfunktionen spezialisiert sind. Beispielsweise sind Sprosse gut an ein schnelles Wachstum angepasst, w&#xE4;hrend Wurzeln so aufgebaut sind, dass sie Ressourcen effizient aufnehmen. Die Zuckerproduktion ist jedoch haupts&#xE4;chlich auf die photosynthetischen Gewebe beschr&#xE4;nkt, die sich in den Bl&#xE4;ttern von Bedecktsamern befinden. Zucker und andere Ressourcen werden durch einen Prozess, der als Translokation bezeichnet wird, von photosynthetischen Zellen zu anderen spezialisierten Geweben transportiert.
Innerhalb einer Pflanze werden Gewebe, die mehr Zucker produzieren, als sie verbrauchen, als Zuckerquellen bezeichnet &#x2013; Bl&#xE4;tter sind das wichtigste Beispiel hierf&#xFC;r. Wurzeln, Sprosse, Bl&#xFC;ten und Fr&#xFC;chte gelten gew&#xF6;hnlich als Zuckersenken, da sie mehr Zucker ben&#xF6;tigen, als sie selbst produzieren k&#xF6;nnen. Die Translokation verteilt Zucker, Hormone, Aminos&#xE4;uren und einige Signalmolek&#xFC;le von Zuckerquellen zu Zuckersenken durch eine r&#xF6;hrenf&#xF6;rmige Struktur in Gef&#xE4;&#xDF;pflanzen, die als Phloem bezeichnet wird. Der Fluss kann im Phloem bidirektional verlaufen. Das Phloem besteht aus Zellen, die durch Siebplatten an ihren Enden miteinander verbunden sind und die Siebr&#xF6;hrenglieder bilden. Diese Zellen besitzen verdickte Zellw&#xE4;nde, die ihnen mechanische Stabilit&#xE4;t verleihen, und werden von benachbarten Geleitzellen begleitet, die zur Funktionsf&#xE4;higkeit des Phloems beitragen und die Beladung des Phloems mit L&#xF6;sungen aus den umliegenden Geweben erleichtern.
Die Phloembeladung kann &#xFC;ber den apoplastischen oder den symplastischen Weg erfolgen und entweder passiv oder aktiv sein. Diese Transportwege zum Phloem k&#xF6;nnen gleichzeitig oder nacheinander genutzt werden, und es gibt Hinweise darauf, dass Pflanzen abh&#xE4;ngig vom Wasser- und Energiebedarf der Pflanze zwischen den Beladungsmodi wechseln k&#xF6;nnen. In vielen F&#xE4;llen koppelt der Saccharose/H+-Symporter die Beladung des Phloems mit Saccharose an den Transport eines Wasserstoffions.
Gem&#xE4;&#xDF; der Druckstromhypothese f&#xF6;rdert der Zuckerkonzentrationsgradient den Einstrom von Wasser in das Phloem, wodurch es zur Druckerzeugung kommt. Infolgedessen bewegt sich der Phloemsaft zur n&#xE4;chstgelegenen Zuckersenke, in deren Bereich ein niedrigerer Druck herrscht. An der Zuckersenke wird Saccharose in den Bereich mit der niedrigeren Zuckerkonzentration transportiert, wodurch ihr Austritt aus dem Phloem angetrieben wird. Das Wasser folgt der Saccharose und verringert den Druck im Phloem.

Phloem und Zuckertransport

Like many living organisms, plants have tissues that specialize in specific plant functions. For example, shoots are well adapted to rapid growth, while ...

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Education

Lehre

JoVE Core

Biology

Biologie

Plant Biology

Pflanzenbiologie

Plant Structure, Growth and Function

Pflanzenstruktur, Wachstum und Ernährung

KEY TERMS AND CONCEPTS

KERNBEGRIFFE UND KONZEPTE

how phloem moves sugars in plants

Phloem moves sugars and other materials through plants. In angiosperms, sugar production is mostly limited to photosynthetic cells in the leaves. These leaves act as sugar sources because they make more sugar than they use. Roots, shoots, flowers, and fruits are usually sugar sinks because they need more sugar than they can make.

This movement is called translocation. It carries sugar, hormones, amino acids, and some signaling molecules from source tissues to sink tissues. The transport pathway is a tube-like part of the vascular system called phloem. Flow in the phloem can move in both directions, depending on where the plant needs resources.

Phloem is built from sieve-tube elements that are joined end to end by plasmodesmata. These cells have thickened cell walls, which help support the tissue. Companion cells sit next to them and help keep the phloem healthy. They also help load solutions into the phloem from nearby tissues.

Phloem loading can happen through the apoplastic route or the symplastic route. It may be passive or active. These pathways can work at the same time or one after the other. Some evidence suggests that plants can switch loading modes based on water needs and energy demands. In many cases, a sucrose/H+ symporter helps move sucrose into the phloem together with a hydrogen ion.

The pressure-flow hypothesis explains how sap moves through phloem. As sugar builds up, water moves into the phloem by osmosis and creates pressure. The sap then flows toward the nearest sugar sink, where pressure is lower. At the sink, sucrose moves out into the area with lower sugar concentration. Water follows the sucrose, and pressure in the phloem is reduced.

How Phloem Moves Sugars in Plants

introduction to plant diversity

Plant Adaptations for Life on Land

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basic plant anatomy: roots, stems, and leaves

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Plant Organs and Their Specialized Roles

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xylem and transpiration-driven transport of resources

xylem-and-transpiration-driven-transport-of-resources

How Xylem Moves Water in Plants

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How Guard Cells Open Plant Stomata

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phloem and sugar transport

Phloem moves sugars and other materials through plants. In angiosperms, sugar production is mostly limited to photosynthetic cells in the leaves. These leaves act as sugar sources because they make more sugar than they use. Roots, shoots, flowers, and fruits are usually sugar sinks because they need more sugar than they can make. This movement is called translocation. It carries sugar, hormones, amino acids, and some signaling molecules from source tissues to sink tissues. The transport...

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key terms and concepts

Learn how phloem carries sugar, hormones, and amino acids from leaves to sink tissues using sieve tubes, companion cells, and pressure-flow transport.

How Phloem Moves Sugars in Plants | JoVE K12

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new-york-state-science-learning-standards

New York State Science Learning Standards

Structure and Function

HS-LS1-2.

Georgia Standards of Excellence

9-12

Botany

SBO1.

Transport

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How Phloem Moves Sugars in Plants

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