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First teaching 2023

First exams 2025

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Plant Transverse Sections (CIE AS Biology)

Revision Note

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Cara Head

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Cara Head

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Transverse Sections: Stems, Roots & Leaves

Dicotyledonous (dicots) plants

  • Dicotyledonous (dicots) plants have:
    • Seeds that contain two cotyledons (seed leaves)
    • Network of veins
    • Leaves that typically have broad blades (leaf surface) and petioles (stalks)
    • Tap root with lateral branches
  • Herbaceous dicots have a relatively short life cycle (one growing season) and non-woody tissue

Transport systems

  • Plants need transport systems to meet their metabolic demands (glucose, hormones, mineral ions are required for various processes within plants), to 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

Dicotyledons Plan Diagrams

Transverse sections_Stems, roots and leaves (leaf), downloadable AS & A Level Biology revision notes

Transverse sections_Stems, roots and leaves (stem)

Transverse sections_Stems, roots and leaves (root)

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. 

plant transverse section to draw

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)

plant transverse section example drawing

Plan diagram of transverse root tissue

So, the 'before-and-after' images look like this side-by-side:

root-transverse-sections

Examiner Tip

When drawing tissue plan diagrams (which is common in the practical paper 3) you need to:

  • Read the instructions carefully
  • Draw a large diagram
  • Use a sharp pencil and do not shade (including the nucleus)
  • Use clear, continuous lines
  • When using an eyepiece graticule, use it to ensure you have correct proportions or if you are not using a microscope then endeavour to keep the proportions between tissues to scale
  • If drawing from a low-power image:
    • Do not draw individual cells
    • Read the question carefully as you may only have to draw a portion of the image
    • Include the magnification on the drawing
  • If drawing from a high-power image:
    • Draw only a few of the required cells
    • Draw the cell wall of the plant cells
    • Include the magnification on the drawing
  • When labelling, remember:
    • Use a ruler for label lines (and scale line if appropriate)
    • Label-lines should stop exactly at the structure (do not use arrows)
    • Don't cross label-lines over each other
    • Label all tissues and relevant structures (those requested)

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Cara Head

Author: Cara Head

Expertise: Biology

Cara graduated from the University of Exeter in 2005 with a degree in Biological Sciences. She has fifteen years of experience teaching the Sciences at KS3 to KS5, and Psychology at A-Level. Cara has taught in a range of secondary schools across the South West of England before joining the team at SME. Cara is passionate about Biology and creating resources that bring the subject alive and deepen students' understanding