7.2.8

Phloem Structure

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Phloem Structure

The phloem are plant vessels that are responsible for transporting sugars. The structure of the phloem is specialised for this role.

Sieve tube elements

Sieve tube elements

  • Sieve tube elements are the cells that make up the phloem vessel.
  • The vessel consists of many sieve tube elements that run up the stem on top of one another.
  • Sieve tube elements are living cells that contain a cytoplasm but no nucleus.
  • The walls of sieve tube elements are made of cellulose.
Companion cells

Companion cells

  • Companion cells are connected to sieve tube elements via plasmodesmata.
    • Plasmodesmata allows the cytoplasm to be shared between companion cells and sieve tube elements.
  • Companion cells have a nucleus.
Sieve plates

Sieve plates

  • At either end of the sieve tube elements are sieve plates.
  • Sieve plates have large pores that allow sap to move through the sieve tube elements.
  • Sieve plates allow sugars to be transported through the phloem.
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Water

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Unity & Diversity - Cells

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Introduction to Cells

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DNA Replication, Transcription & Translation

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2.7

Cell Respiration

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Photosynthesis

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Viruses

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3

Unity & Diversity - Organisms

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Diversity of Organisms

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Natural Selection

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5

Form & Function - Molecules

5.1

Carbohydrates & Lipids

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5.2

Proteins

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6

Form & Function - Cells

6.1

Membranes & Membrane Transport

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Form & Function - Organisms

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Gas Exchange

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8

Form & Function - Ecosystems

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Carbon Cycle

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Interaction & Interdependence - Molecules

9.1

Enzymes

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9.2

Metabolism

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Cell Respiration

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9.4

Photosynthesis

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Ecological Niches

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Interaction & Interdependence - Organisms

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Integration of Body Systems

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Defence Against Disease

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Continuity & Change - Molecules

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Continuity & Change - Cells

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Continuity & Change - Organisms

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Continuity & Change - Ecosystems

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Practice questions on Phloem Structure

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  1. 1
    Which of the following statements about phloem structure are true?True / false
  2. 2
    What is the role of sieve plates?Multiple choice
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Investigating Transpiration Rate

Translocation