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Biology AS CIE

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  1. 1-cell-structure
    10 主题
  2. 2-biological-molecules
    19 主题
  3. 3-enzymes
    13 主题
  4. 4-cell-membranes-and-transport
    16 主题
  5. 5-the-mitotic-cell-cycle
    8 主题
  6. 6-nucleic-acids-and-protein-synthesis
    9 主题
  7. 7-transport-in-plants
    11 主题
  8. 8-transport-in-mammals
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  9. 9-gas-exchange
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  10. 10-infectious-diseases
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  11. 11-immunity
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课 7, 主题 11
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7-1-structure-of-transport-tissues AS plant-transverse-sections

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Exam code:9700

Transverse sections: stems, roots & leaves

Transport systems

  • Plants need transport systems to:

    • Meet their metabolic demands (glucose, hormones, mineral ions are required for various processes within plants)

    • Efficiently move substances up and down, e.g.

      • Glucose from photosynthesis needs to be transported to parts of the plant that cannot photosynthesise

      • Water from the roots needs to be transported to the upper parts of a plant

      • Plants may store glucose in storage organs, e.g. tubers, and need to release this glucose and transport it to metabolically active parts of the plant

  • Plants consist of many layers of cells and so cannot rely on diffusion from cell to cell to supply all their needs, as this would be too slow

  • Plants therefore have a vascular system which involves a network of vessels (vascular tissue) running through the leaves, stem and roots

    • These three parts are the main organs involved in transport

  • The vascular system is comprised of two distinct types: 

    • Xylem transports water and mineral ions from the roots to the rest of the plant

    • Phloem transports substances from the source (e.g. a leaf) to the sink (e.g. root)

  • The xylem and phloem are arranged together in vascular bundles

  • The bundles are laid out differently in the leaves, stem and roots

Diagram of a plant showing parts of a leaf and root. Labels detail leaf veins, tap root, palisade and spongy mesophyll, xylem, phloem, and epidermis layers.
Diagram of plant stem structure, labelled with parts: stem, network of veins, tap root, vascular bundle, pith, epidermis, cortex, cambium, phloem, xylem.
Diagram of a plant showing parts of a root and leaf. Labels: network of veins, tap root, root, cortex, epidermis, phloem, xylem, pericycle, endodermis.
Tissue plan diagrams of a dicotyledonous leaf, stem and root

Worked Example

The micrograph below shows a transverse section of root tissue. 

Draw a plan diagram of this section of root tissue. 

Electron micrograph of transverse root tissue
Electron micrograph of transverse root tissue

Step 1 Draw the outlines of each section 

Use a sharp pencil with no shading or sketching

Use a continuous line

Step 2 Add in a few required cells or structures

As this is to be a drawing of an image at high power you can add some simple details to distinguish between sections such as the xylem tissue at the centre of the root

Step 3 Add labels

Use a ruler to draw horizontal lines to each structure of interest

Label clearly with correct spelling

Step 4 Add magnification (if present on micrograph or question)

Diagram of a plant root cross-section showing labelled layers: epidermis, cortex, endodermis, xylem, and phloem arranged from outer to inner.
Plan diagram of transverse root tissue

The ‘before-and-after’ images look like this side-by-side:

<img alt=”Cross-section of a plant root showing layers: cortex, phloem, xylem, endodermis, and epidermis. Left: coloured detail; right: labelled diagram.” data-nimg=”1″ decoding=”async” height=”483″ loading=”lazy” sizes=”(max-width: 320px) 320w, (max-width: 640px) 640w, (max-width: 960px) 960w, (max-width: 1280px) 1280w, 1920w” src=”https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=3840/https://cdn.savemyexams.com/uploads/2025/09/53254_httpscdn-savemyexams-comuploads202310root-transverse-sections.png” srcset=”https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=16/https://cdn.savemyexams.com/uploads/2025/09/53254_httpscdn-savemyexams-comuploads202310root-transverse-sections.png 16w, https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=32/https://cdn.savemyexams.com/uploads/2025/09/53254_httpscdn-savemyexams-comuploads202310root-transverse-sections.png 32w, https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=48/https://cdn.savemyexams.com/uploads/2025/09/53254_httpscdn-savemyexams-comuploads202310root-transverse-sections.png 48w, https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=64/https://cdn.savemyexams.com/uploads/2025/09/53254_httpscdn-savemyexams-comuploads202310root-transverse-sections.png 64w, https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=96/https://cdn.savemyexams.com/uploads/2025/09/53254_httpscdn-savemyexams-comuploads202310root-transverse-sections.png 96w, https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=128/https://cdn.savemyexams.com/uploads/2025/09/53254_httpscdn-savemyexams-comuploads202310root-transverse-sections.png 128w, https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=256/https://cdn.savemyexams.com/uploads/2025/09/53254_httpscdn-savemyexams-comuploads202310root-transverse-sections.png 256w, https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=384/https://cdn.savemyexams.com/uploads/2025/09/53254_httpscdn-savemyexams-comuploads202310root-transverse-sections.png 384w, https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=640/https://cdn.savemyexams.com/uploads/2025/09/53254_httpscdn-savemyexams-comuploads202310root-transverse-sections.png 640w, https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=750/https://cdn.savemyexams.com/uploads/2025/09/53254_httpscdn-savemyexams-comuploads202310root-transverse-sections.png 750w, https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=828/https://cdn.savemyexams.com/uploads/2025/09/53254_httpscdn-savemyexams-comuploads202310root-transverse-sections.png 828w, https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=1080/https://cdn.savemyexams.com/uploads/2025/09/53254_httpscdn-savemyexams-comuploads202310root-transverse-sections.png 1080w, https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=1200/https://cdn.savemyexams.com/uploads/2025/09/53254_httpscdn-savemyexams-comuploads202310root-transverse-sections.png 1200w, https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=1920/https://cdn.savemyexams.com/uploads/2025/09/53254_httpscdn-savemyexams-

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