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Title: The movement of organic solutes through plants
Description: includes movement through the Phloem tissues and the mass flow hypothesis, this is from my first year of A level biology
Description: includes movement through the Phloem tissues and the mass flow hypothesis, this is from my first year of A level biology
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The movement of organic solutes through the plant
Scientists and models
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Scientific advances begin with a model to explain something
Based on available evidence at that time
Debates stimulate, make predictions (what would happen if model is correct)
Collaboration, ingenuity, think objectively= reliable investigations to test a model
More predictions shown correct= widely accepted
Sometimes it takes just one investigation to show a prediction is incorrect
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Cohesion-tension model offers a wide range of scientific explanations= widely accepted
Transport in the phloem is less clear and mass-flow model has many unanswered
questions/incomplete explanation or better explanations out there
The movement of solutes through phloem tissue
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Transport of sugars (sucrose) through sieve tubes is easily demonstrated using radioactively
labelled carbon dioxide
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The mass-flow hypothesis of phloem transport
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Method of transport in which pressure differences are used to move a fluid to carry
substances in one direction
Pressure differences generated in different parts of the plant
Sugars made by photosynthesis dissolve in cytoplasm= lowered water potential
So, water enters cell by osmosis= high hydrostatic pressure (source area)
Sugars used up rapidly in respiration/converted to starch (insoluble, forms starch grains
which have no osmotic effect)
Water potential raises- water flows out= low hydrostatic pressure (sink area)
Pressure difference forces sugars into sieve tubes at source, induces mass-flow through
phloem towards sink
Title: The movement of organic solutes through plants
Description: includes movement through the Phloem tissues and the mass flow hypothesis, this is from my first year of A level biology
Description: includes movement through the Phloem tissues and the mass flow hypothesis, this is from my first year of A level biology