experiments that show the movement of substances in xylem and phloem
DESCRIPTION
Experiments that show the movement of substances in xylem and phloem. How can we show that water is being transported in the xylem?. Using these materials…. Red ink A plant (eg celery) Microscope Knife. Examine the section under microscope. Transverse sectioning of stem. - PowerPoint PPT PresentationTRANSCRIPT
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Using these materials…
• Red ink • A plant (eg celery)• Microscope• Knife
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Transverse sectioning of stem
Examine the section under microscope
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Under the microscope……
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Evidence
• Xylem stained red.
• Water is being transported in the xylem.
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Translocation
• Transportation of manufactured food products (sugars and amino acids) in the phloem is known as translocation.
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Leaves •Source•Location where food is manufactured
Fruits/roots •Sink •Location where food is being transported to.
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Movement of sugars in the phloem
• Using aphids• Using carbon-14 isotopes. • Using the ’ringing experiment’
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Using aphids
Feed on the stems
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Carbon dioxide
Sieve tubes
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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.
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Think about it!
• Why do plantations infested with aphids have reduced fruit yield?
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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?
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Using the ringing experiment
• The region above the cut end swells due to the accumulation of sugar.
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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.
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Use of radioactive Carbon-14 isotopes
12CO2
14CO2Radioactive
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14CO2 + H20 14C6H1206 + C02 + H20
Use of radioactive Carbon-14 isotopes
Sugar transported in the phloem also show radioactivity.
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Cross section of stem
Put an x ray film on top
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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.
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Think about it!
Young leaf exposed to carbon dioxide.
No radioactivity detected . Why?