Investigating translocation

• Complete the following about investigating translocation.

  • Can be investigated using tracer and ringing experiments
  • proves phloem transports sugars not xylem
• How does tracing work?

  • Involves radioactively labelling carbon - used in photosynthesis
  • create sugars with this carbon
  • thin slices from stems are cut and placed on X-ray film which turns black when exposed to radioactive material
  • stems will turn black as that is where phloem are
• Describe what happens in ringing experiments.

  • Ring of bark (and phloem) is peeled and removed off a trunk
  • consequently, the trunk swells above the removed section
  • analysis will show it contains sugar
  • when phloem removed, sugar cannot be transported