Transport systems in dicotyledonous plants

• Need for transport systems in multicellular plants - Size:

  • Need an effect transport system to move substances up and down from tip of the roots to topmost leaves
• Need for transport systems in multicellular plants - Metabolic demands:

  • Many internal parts don't photosynthesise
  • Transport of oxygen and glucose
  • Waste products of metabolism removed
  • Transports of hormones made in one part of the body needing to transported to another
  • Mineral ions absorbed by roots - Transport to all cells for protein production - For enzymes and structure of the cell
• Need for transport systems in multicellular plants - SA:V ratio:

  • Leaves - Large SA:V ratio for gaseous exchange
  • Stems, trunks and roots have small SA:V ratio - Cannot be heavily relied on
• Structure and function of xylem

  • Transport water and mineral ions
  • Support of the plant
  • Non living tissue
  • Long and hollow - Columns of cells fusing together
  • Parenchyma packs - Store food + Contain tannin deposits (Bitter tasting warding away herbivores)
  • Lignified walls - Extra mechanical strength + Don't transport water
  • Unlignified walls - Water leaves xylem to move to other parts of the plant
• Structure and function of the phloem

  • Transports food through organic solutes around the plant from the leaves where they are made during photosynthesis

  Sieve tube elements:

  • Cell joined end to end forming long, hollow structure
  • Unlignified
  • Sieve plates - Perforated areas in between STE

  Companion cells:

  • Form with STE
  • Linked by plasmodesmata - Microscopic channels through cell walls - Link cytoplasm with adjacent cells
  • Life support systems for sieve tube cells