In this lab, how will you measure how high the eosin orange dye travels up the stem?

Question

BlackTom AI · Accepted Answer

Xylem vessels within vascular bundles conduct water and dissolved dye upward, so observing eosin orange in those bundles is the direct way to measure how far the dye has traveled up the stem.

1) Relevant knowledge points and concepts
- Plant vascular tissue: xylem (part of vascular bundle) transports water and dissolved substances from roots upward; phloem transports sugars downward and laterally.
- Dyes like eosin orange move with the transpiration stream through xylem, staining the xylem elements in vascular bundles.
- Measuring travel distance requires identifying the highest location where xylem (vascular bundle) is stained.

2) Step-by-step experimental reasoning
- Place the cut stem in eosin orange solution and allow transpiration to pull the dye upward.
- After a set period, remove the stem and make transverse or longitudinal sections at known distances from the cut base.
- Examine each section for orange staining specifically in the vascular bundle (xylem) tissue.
- Record the highest section where dye is visible within the vascular bundle; that distance is the dye travel height.

3) Intermediate steps and measurements
- Mark the stem at regular intervals (e.g., every 1 cm).
- After staining, check marks: if xylem at 5 cm is stained but at 6 cm is not, the dye traveled to 5 cm.
- If using microscopy, confirm staining is inside xylem cells of the vascular bundle, not surface residue.

4) Why the correct answer is correct
- The vascular bundle contains the xylem channels that actually conduct the dye; presence of dye there directly indicates how far the transpiration stream transported the dye.

5) Why other options are incorrect
- Mitochondria: intracellular organelles, not the pathway for bulk upward transport; dye movement is tissue-level, not mitochondrial.
- Leaves: dye may reach leaves, but leaf staining alone doesn’t specify how far up the stem the dye moved through vascular bundles at particular stem heights.
- Flowers: like leaves, flower staining is not a precise measure of stem transport height and may be affected by local distribution.

Conclusion: Observing the presence of dye in the vascular bundle is the correct method to measure how high eosin orange travels up the stem, matching the provided answer.

In this lab, how will you measure how high the eosin orange dye travels up the stem?单项选择题

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