TRANSLOCATION Flashcards

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1
Q

describe phloem

A

alive but few organelles
rely on companion cells (carry out respiration) to keep them alive
have ends that form sieve plates where cytoplasm can pass
no lignin in walls so walls are permeable to water and solutes

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2
Q

what is translocation

A

process where organic and some inorganic ions are transported from one part of a plant to another
sugars (formed during photosynthesis) at a source need to be transported to be used or stored at a sink

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3
Q

describe the mass flow theory

A
  1. sucrose are actively transported from source cells to companion cells to sieve tubes
  2. this lowers the water potential so water moves into the sieve tubes via osmosis
  3. a high pressure is created in sieve tubes near source cells
  4. since solutes are used in respiration / stored in sink cells a pressure gradient is created
    water and solutes move down the pressure gradient
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4
Q

what three evidences are there for the mass flow theory

A

ringing experiment
radioactive tracers
aphids

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