Plan a stain investigation of the shoot water pathway
Design a supervised investigation that follows a suitable stain through conducting tissues.
Section B8.2 · Water uptake
Mapped to the named 0654 section using teaching from the corresponding single-science course. A 0654-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade.
Before you begin
- Recall the water route and controlled investigations.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What is a comparison control?
What you will learn
- Describe a suitable above-ground water-path investigation
- Explain controls, sectioning and practical limits
Follow the coloured solution
In a teacher-supervised investigation, place freshly cut, suitable leafy shoots in a safe prepared water-soluble stain. Keep an unstained water-only shoot for comparison. Record the starting state and allow a stated interval under matched light, temperature and air movement.
The teacher prepares thin stem and leaf-vein sections using the laboratory’s safe blade procedure. Compare the coloured regions with a tissue key. Staining of xylem provides evidence that the solution travelled along that tissue in the shoot.
Keep the question narrow
Match shoot type, size, initial condition, immersion depth, stain concentration and elapsed time. Prevent coloured solution from splashing onto outside surfaces; otherwise external colour can mimic transported stain. Replicate with comparable shoots and record variation.
A cut shoot tests an above-ground pathway; it bypasses the intact root. Stain movement is a tracer observation and may differ from pure-water behaviour. Reading and explaining this method does not establish that you have performed the investigation competently.
Sources for this lesson
Pause and explain
Which result supports the shoot water pathway?
Worked example
Why include a water-only shoot when looking for stain in stem sections?
Show the worked solution
- It shows the tissue appearance without added tracer.
- Comparison helps distinguish ordinary tissue colour from introduced stain.
Answer The water-only comparison provides an unstained baseline, helping identify introduced stain rather than natural or preparation colour.
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.
List three main stages of the supervised stain method.
Give me a hint
Follow setup, elapsed time and tissue observation.
Compare my reasoning
- Place a suitable cut shoot in prepared stain with a water-only comparison.
- After a stated matched interval, examine teacher-prepared stem/vein sections and identify stained tissues.
Set up stain and control; allow recorded time; inspect sections against a tissue key.
Look for these in your work
- Describe setup and comparison
- Localise the stain in sections
Give four conditions to match between comparable shoots.
Give me a hint
Keep differences other than the stain treatment controlled.
Compare my reasoning
- Match shoot type/size and starting condition.
- Match time, light, temperature and air movement.
For example: shoot type/size, elapsed time, temperature and light; also control air movement and immersion details.
Look for these in your work
- Give four suitable conditions
- Explain that matching limits alternative causes
A teacher wants to test the complete intact-root route. Why is the cut-shoot investigation insufficient?
Give me a hint
Identify the tissues removed from the setup.
Compare my reasoning
- The cut shoot omits root hairs and root cortex.
- It can still test above-ground xylem movement.
It bypasses root uptake and cortex movement; an intact-plant design is needed for evidence about those stages.
Look for these in your work
- Identify the bypassed stages
- Retain the valid shoot-path conclusion
Common mistakes
- Calling surface dye proof of internal transport.
- Claiming a cut shoot demonstrates intact root uptake.
What can you explain now?
Which result supports the shoot water pathway?
Compare with the explanation
Stain within identified xylem in sections
Internal position links the tracer with the conducting tissue.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Explain what an internal stain result supports and what a cut shoot cannot establish.
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.