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

Fotosynthese maakt suiker in bladeren.
 Maar de suiker is vaak nodig in andere delen van de plant.
 Translocatie is het proces dat de producten van fotosynthese verspreidt naar andere plantenweefsels.
Bladeren worden suikerbronnen genoemd, plekken die meer suiker produceren dan consumeren.
 Wortels, stengels en vruchten daarentegen zijn suikerconsumenten.
 Suikertransport van bron naar consument gebeurt in weefsel genaamd flo&#xEB;em.
In bedektzadigen bestaat flo&#xEB;em uit gespecialiseerde cellen genaamd zeefcellen, die in elkaars verlengde liggen om lange buizen te vormen.
 Begeleidende cellen liggen langs elke zeefcel.
 Suiker kan via verschillende routes bij het flo&#xEB;em komen.
Het kan door de extracellulaire ruimte en celwanden bewegen of door poren die het cytoplasma van buurcellen direct verbinden.
 Als het suiker bij de begeleidende cellen komt, brengen sucrose-waterstof- cotransporters het actief in de zeefcellen.
 Een waterige oplossing genaamd flo&#xEB;emsap, bestaande uit suiker, aminozuren, hormonen en mineralen, stroomt door de zeefcellen.
Volgens de pressure-flowhypothese volgt water de suiker het flo&#xEB;em in door osmose, waardoor de druk in het flo&#xEB;em toeneemt en het flo&#xEB;emsap in beweging komt.
 Het flo&#xEB;emsap stroomt dan naar het dichtstbijzijnde consumerende weefsel, dat een lage suikerconcentratie heeft.
 Het suiker diffundeert of wordt actief uit het flo&#xEB;em getransporteerd.
Als het suiker uit het flo&#xEB;em gaat, volgt water door osmose, zodat de druk in het flo&#xEB;em afneemt.
 Door translocatie in het flo&#xEB;em kunnen planten middelen naar de weefsels brengen waar ze nodig zijn op een bepaald moment of seizoen.

floëem en suikertransport

Net als veel andere levende organismen hebben planten weefsels die gespecialiseerd zijn in specifieke plantfuncties. Scheuten zijn bijvoorbeeld goed aangepast aan snelle groei, terwijl wortels zo zijn opgebouwd dat ze hulpbronnen effici&#xEB;nt opnemen. De suikerproductie is echter voornamelijk beperkt tot de fotosynthetische weefsels in de bladeren van bedektzadige planten. Suiker en andere hulpbronnen worden via een proces dat translocatie wordt genoemd van fotosynthetische cellen naar andere gespecialiseerde weefsels getransporteerd.
Binnen een plant zijn weefsels die meer suiker produceren dan ze verbruiken suikerbronnen - bladeren zijn hiervan het belangrijkste voorbeeld. Wortels, scheuten, bloemen en vruchten worden doorgaans beschouwd als suikersinks, omdat ze meer suiker nodig hebben dan ze zelf kunnen produceren. Translocatie verdeelt suiker, hormonen, aminozuren en bepaalde signaalmoleculen vanuit suikerbronnen naar suikersinks via een buisvormige structuur in vaatplanten die flo&#xEB;em wordt genoemd. De stroming in het flo&#xEB;em kan bidirectioneel zijn. Het flo&#xEB;em bestaat uit cellen die via zeefplaten met hun uiteinden aan elkaar zijn verbonden en zo de zeefbuiselementen vormen. Deze cellen hebben verdikte celwanden, die hun mechanische ondersteuning bieden, en worden vergezeld door aangrenzende begeleidende cellen die het goed functioneren van het flo&#xEB;em en het inladen van oplossingen in het flo&#xEB;em vanuit omliggende weefsels bevorderen.
Het laden van het flo&#xEB;em kan via de apoplastische of symplastische routes plaatsvinden en kan passief of actief zijn. Deze routes naar het flo&#xEB;em kunnen gelijktijdig of na elkaar functioneren, en er zijn aanwijzingen dat planten tussen laadwijzen kunnen wisselen, afhankelijk van de water- en energiebehoeften van de plant. In veel gevallen koppelt de sacharose/H+-symporter het laden van sacharose in het flo&#xEB;em aan het transport van een waterstofion.
Volgens de drukstroomhypothese bevordert de suikerconcentratiegradi&#xEB;nt de instroom van water in het flo&#xEB;em, wat resulteert in de opbouw van druk. Als gevolg daarvan stroomt het flo&#xEB;emsap naar gebieden met een lagere druk, bij de dichtstbijzijnde suikersink. Bij de suikersink wordt sacharose naar het gebied met een lagere suikerconcentratie getransporteerd, waardoor sacharose uit het flo&#xEB;em stroomt. Het water volgt de sacharose en vermindert de druk in het flo&#xEB;em.

Floëem en suikertransport

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

JoVE Core

Biology

Biologie

Plant Biology

Plantenbiologie

Plant Structure, Growth and Function

Plantstructuur, groei en voeding

KEY TERMS AND CONCEPTS

BELANGRIJKE TERMEN EN CONCEPTEN

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

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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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biology

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New York State Science Learning Standards

Structure and Function

HS-LS1-2.

Georgia Standards of Excellence

9-12

Botany

SBO1.

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How Phloem Moves Sugars in Plants

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