OCR - A-Level - Biology - Transport in Plants


A level Biology (To Be Printed) Flowchart on OCR - A-Level - Biology - Transport in Plants, created by Josh Anderson on 25/03/2017.
Josh Anderson
Flowchart by Josh Anderson, updated more than 1 year ago
Josh Anderson
Created by Josh Anderson over 6 years ago

Resource summary

Flowchart nodes

  • Transport in Plants
  • Xylem
  • Phloem
  • Types of Xylem cell
  • Xylem vessel consist of dead hollow cells with lignified walls, making them waterproof
  • Linked end to end to create a hollow tube, with sidewalls that allow lateral movement of water
  • Parenchyma
  • Living cells with thin walls
  • Can store water, turgidity for support
  • Fibres
  • Lignified walls to provide strength
  • Water enters through root hair cells. Moves into xylem in the centre. All due to osmosis (cell sap has (in)organic molecules dissolved so low Ψ.
  • Moves through symplast or apoplast pathway. Through cell cytoplasm or between cell walls respectively
  • Continuous movement due to next cell having lower Ψ than current.
  • Water evaporates in leaf, then leaves through stomata (transpiration).
  • When water leaves, water from the top of the xylem is pulled into the leaf down water concentration gradient
  • Results in pressure at top being lower than pressure at bottom, pushing water up xylem
  • Surface tension, adhesion, etc. keeps water moving up xylem
  • All due to osmosis
  • Types of Phloem cell
  • Sieve tube elements - living tubular cells connected end to end. Ends have perforations (sieve plates)
  • Companion cells are next to sieve tube elements (one each)
  • Contains the organelles that sieve tube elements lack
  • Controls movement of solutes and provides ATP
  • Connected via plasmodesmata (strands of cytoplasm)
  • Parenchyma and Fibres
  • See Types of Xylem cell
  • Translocation
  • Movement of organic substances around the plant
  • Requires energy(active process)
  • Sucrose loaded (actively) into phloem at source (photosynthesising leaf)
  • Hydrogen ions pumped out of the companion cell (ATP), creating a concentration gradient
  • H+ ions diffuse back in through cotransporter proteins that allow H+ in if with sucrose molecules
  • Cotransport(secondary active transport)
  • Sucrose diffuses down the concentration gradient
  • Water moves in by osmosis because Ψ decreases
  • Sucrose unloaded into a sink, usually by diffusion before being converted to something else to maintain the concentration gradient
  • Mass flow of substances in phloem
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