Module 3: Transport Systems in Plants

These free OCR A Level Biology Transport Systems in Plants revision notes have been written for specification points 3.1.3(a).

  1. Exchange Surfaces
  2. Mammalian Gaseous Exchange System
  3. Mammalian Ventilation
  4. Oxygen Uptake in Mammals
  5. Measuring Oxygen Uptake in Mammals
  6. Ventilation and Gas Exchange in Gills
  7. Ventilation and Gas Exchange in Insects
  8. Transport Systems in Animals
  9. Blood Vessels
  10. The Heart
  11. Haemoglobin and Red Blood Cells
  12. Tissue Fluid Formation
  13. Transport Systems in Plants
  14. Plant Vascular Systems
  15. Plant Transport of Water
  16. Plant Adaptations to Water
  17. Translocation
The Need For Transport Systems

Multicellular plants cannot fulfil their metabolic needs or excrete all waste by diffusion alone.

The table below outlines the limitations which make diffusion insufficient:

LimitationExplanation
Low surface area to volume ratioAs plants increase in size, diffusion of substances via the outer
surface cannot keep up with internal demands.
Metabolic activityRegions of high growth (e.g. meristems, leaves and storage organs)
need a constant supply of substrates and to remove excess products.
Diffusion distanceMany specialised cells are too far away from the source of a metabolic
input (e.g. leaves from water, or roots from sucrose).
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