9.2 Transport in the phloem of plants
IB Syllabus Statements
Understandings:
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Plants transport organic compounds from sources to sinks.
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Incompressibility of water allows transport along hydrostatic pressure gradients.
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Active transport is used to load organic compounds into phloem sieve tubes at the source.
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High concentrations of solutes in the phloem at the source lead to water uptake by osmosis.
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Raised hydrostatic pressure causes the contents of the phloem to flow towards sinks.
Applications and skills:
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Application: Structure–function relationships of phloem sieve tubes.
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Skill: Identification of xylem and phloem in microscope images of stem and root.
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Skill: Analysis of data from experiments measuring phloem transport rates using aphid stylets and radioactively-labelled carbon dioxide.
Videos
Phloem and Hydrostatic Gradients
Measuring phloem transport rates
Phloem Structure and Function
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Topic 9.2 Transport in the phloem of plants HookED SOLO Hexagons
Topic 9.2 Transport in the phloem of plants SSaQ (Syllabus Statement as Questions)
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Explain the phrase ‘plants transport organic compounds from sources to sinks’.
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Explain how hydrostatic pressure gradients can be formed because of the incompressibility of water.
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What process allows organic compounds (e.g. Sucrose) to be loaded into phloem sieve tubes?
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What is responsible for water being taken up into phloem sieve tubes?
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How does hydrostatic pressure contribute to movement of the content inside phloem sieve tubes?
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Outline the relationship between the structure and function of phloem sieve tubes.
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Outline how you would use visual cues to identify xylem and phloem in microscope images of stems and roots.
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Explain how radioactively-labeled carbon dioxide is used in combination with aphid stylets to measure phloem transport rates.