Locate transport tissues in a dicot root diagram
Recognise central xylem and phloem between its arms in a young non-woody dicot root.
Section B8.1 · Xylem and phloem
Cross-referenced to the 2028–2029 0653 section using original teaching from the related single-science courses. A 0653-specific objective-by-objective and Core/Supplement review is in progress. Written practice is self-checked and does not demonstrate supervised laboratory competence or award an official Cambridge grade.
Before you begin
- Distinguish an organ from a tissue.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What does a transverse section show?
What you will learn
- Locate xylem relative to the root centre
- Locate phloem between xylem arms
Read the whole section first
A transverse section cuts across the root, so it shows tissue positions rather than the direction of flow along the root. In this young non-woody dicot model, a central star-shaped region represents xylem. Phloem occupies patches between the xylem arms.
The outer epidermis and the cortex surround the central transport region. Establish the centre before labelling; the ring of outer cells is not phloem merely because it encircles the root.
Connect position with function
Once the position is identified, add the function: xylem transports water/mineral ions and supports; phloem transports sucrose/amino acids. A diagram label and a function are different tasks and both can be requested.
This model applies to the stated dicot root. Do not copy the same central-star arrangement onto a stem, a leaf or every monocot root. Schematic colour helps distinguish the drawn regions but is not a universal microscope stain key.
Sources for this lesson
Pause and explain
Where is phloem in this dicot root model?
Worked example
A dicot root diagram marks A at the central star and B between two star arms. Identify A and B.
Show the worked solution
- Find the central star-shaped transport region: A is xylem.
- B lies between its arms: B is phloem.
Answer A: xylem. B: phloem. The cortex surrounds the central transport region.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Identify the central star and the small patches between its arms in the model.
Give me a hint
Use position, then tissue names.
Compare my reasoning
- The central star marks xylem.
- The inter-arm patches mark phloem.
Central star: xylem; patches between arms: phloem.
Look for these in your work
- Locate xylem centrally
- Locate phloem between arms
A label points to the cortex outside the central tissues. A learner calls it phloem. Explain the error.
Give me a hint
Locate the phloem patches more precisely.
Compare my reasoning
- The cortex is outside the central transport region.
- In the supplied model, phloem patches lie between xylem arms.
The label is cortex, not phloem; the phloem is between the central xylem arms.
Look for these in your work
- Distinguish cortex from transport tissue
- Use a positional explanation
The same diagram is rotated 90°. Which tissue labels change, and why?
Give me a hint
Rotation changes the page orientation, not the organ.
Compare my reasoning
- The star remains central xylem.
- The between-arm patches remain phloem.
Neither tissue identity changes. Use relative position, not “top of page”.
Look for these in your work
- Keep identities unchanged
- Explain rotation using relative positions
Common mistakes
- Using the stem bundle-ring arrangement for a root.
- Confusing the outer cortex with phloem.
What can you explain now?
Where is phloem in this dicot root model?
Compare with the explanation
Between the central xylem arms
This is the stated young dicot arrangement.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Sketch a dicot root cross-section and place phloem relative to the xylem arms.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.