chapter 30.5
DESCRIPTION
Chapter 30.5. How Do Organic Compounds Move Through Plants?. AP Biology Spring 2011. Conducting Tubes in Phloem. Phloem: living vascular tissue with organized arrays of conducting tubes, fibers, and parenchyma cells. Conducting Tubes in Phloem. - PowerPoint PPT PresentationTRANSCRIPT
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CHAPTER 30.5How Do Organic Compounds Move Through Plants?
AP BiologySpring 2011
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CONDUCTING TUBES IN PHLOEM
Phloem: living vascular tissue with organized arrays of conducting tubes, fibers, and parenchyma cells
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CONDUCTING TUBES IN PHLOEM
Sieve tube cells: alive at maturity and are interconnected side by side and end to end from the roots to the leaves
Companion cells: located next to sieve tubes and function to actively transport the products of photosynthesis into the sieve tubes
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CONDUCTING TUBES IN PHLOEM
Carbohydrates are mainly stored as insoluble starch molecules that must be converted to more soluble carbohydrates Such as sucrose before being transported
throughout the plant
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TRANSLOCATION
Translocation: transport of sucrose and other compounds through phloem
Movement of molecules through phloem is from sources to sinks Source: mostly leaves Sink: flowers and fruits
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TRANSLOCATION
Observations of plant-sucking insects demonstrates that the sugary fluid in the phloem is under high pressure
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TRANSLOCATION
Pressure flow theory: translocation depends on pressure gradients Solutes are loaded by active transport into the
phloem from a source (ex. Leaves) Water enters by osmosis due to increase in
solutes Pressure builds in sieve tubes pushing the
sucrose-laden fluid out of the source, into the stems, and on the sink (ex. Fruit)
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