Experiments that show the movement of substances in xylem and phloem
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Transcript of Experiments that show the movement of substances in xylem and phloem
Using these materials…
• Red ink • A plant (eg celery)• Microscope• Knife
Transverse sectioning of stem
Examine the section under microscope
Under the microscope……
Evidence
• Xylem stained red.
• Water is being transported in the xylem.
Translocation
• Transportation of manufactured food products (sugars and amino acids) in the phloem is known as translocation.
Leaves •Source•Location where food is manufactured
Fruits/roots •Sink •Location where food is being transported to.
Movement of sugars in the phloem
• Using aphids• Using carbon-14 isotopes. • Using the ’ringing experiment’
Using aphids
Feed on the stems
Carbon dioxide
Sieve tubes
Evidences
• Liquid the exude out of the cut end of the proboscis contain sugar and amino acid.
• Viewed under microscope, proboscis found embedded in the sieve tube.
Think about it!
• Why do plantations infested with aphids have reduced fruit yield?
Using the ringing experiment
• Remove the bark of the tree would remove the phloem and the cambium.
• Predict what would happen at the cut region?
Using the ringing experiment
• The region above the cut end swells due to the accumulation of sugar.
Evidences from ‘ringing’ expt
• Removing of bark remove phloem.
• Swelling above the cut region shows that sugar is being accumulated in that region as phloem transport is being disrupted.
Use of radioactive Carbon-14 isotopes
12CO2
14CO2Radioactive
14CO2 + H20 14C6H1206 + C02 + H20
Use of radioactive Carbon-14 isotopes
Sugar transported in the phloem also show radioactivity.
Cross section of stem
Put an x ray film on top
Evidences
• Plants exposed to radioactive 14CO2 would contain radioactive sugar in the phloem.
• The presence of radioactive sugars is detected by an x-ray film.
Think about it!
Young leaf exposed to carbon dioxide.
No radioactivity detected . Why?