Transport system in plants

• Plants require water for


  • Transporting materials such as minerals
  • Photosynthesis
  • Maintenance of turgidity
• Plants take up water and minerals

  1. Osmosis into root epidermis

  2. Through root hair cells

  3. Into xylem vessels
• Xylem cells


  • Made of dead cells
  • Walls contain lignin to withstand pressure changes
• Water and minerals transported

  1. From roots and stems

  2. To leaves through xylem vessels
• Water enters leaves

  1. Into xylem vessels

  2. Passes into spongy mesophyll cells by osmosis

  3. Evaporates into spaces

  4. Diffuses out through stomata
• Transpiration


  Process of water moving through a plant and evaporating through stomata
• Transpiration rate affected by

  • Wind speed
  • Humidity
  • Temperature
  • Plant surface area
• Sugars transported


  1. From photosynthetic tissues

  2. Through phloem tubes

  3. To all parts of plant
• Phloem cells


  • Living cells
  • Able to transport sugars
• Xylem


  Transports water and minerals into leaves
• Phloem


  Transports sugars around the plant
• Key words


  • Companion cell
  • Guard cells
  • Leaf epidermis
  • Lignin
  • Minerals
  • Palisade mesophyll
  • Phloem
  • Potometer
  • Root epidermis
  • Root hair cell
  • Sieve tube cell
  • Spongy mesophyll
  • Stomata
  • Transpiration
  • Transpiration rate
  • Vein
  • Xylem vessels
• The xylem transports water from the roots to the leaves, while phloem transports sugars made by photosynthesis.
• Xylem is composed of tracheids or vessel elements that are dead cells with thickened walls containing lignin.
• Water is absorbed through root hairs and moves upwards through the xylem vessels towards the leaves.
• As water evaporates from the leaf surface, it creates negative pressure (tension) within the xylem vessels, which pulls more water upwards.
• The phloem consists of sieve-tube elements joined together by perforated plates, allowing solutes to pass freely between them.
• Sugar molecules move downward along the concentration gradient from source to sink tissues via active transport.
• Plants need water to maintain turgidity, for photosynthesis, and to keep cool
• Turgidity


  The state of plant cells being swollen and rigid, which keeps the plant upright
• Water entry into plants

  1. Water enters roots by osmosis

  2. Water moves up through xylem vessels
• Xylem


  • Hollow, dead tubes that transport water upwards
  • Supported by lignin rings
• Phloem


  • Transports sugars up and down the plant
  • Living cells with companion cells that provide energy
• Parts of a leaf

  • Cuticle
  • Upper epidermis
  • Palisade mesophyll
  • Spongy mesophyll
  • Lower epidermis
  • Veins
• Stomata


  Small pores on the underside of leaves that allow gas exchange
• Guard cells


  Cells that control the opening and closing of stomata
• Transpiration


  1. Water enters roots

  2. Water moves up through xylem

  3. Water evaporates from open stomata
• High light intensity


  Increases transpiration rate
• High temperature


  Increases transpiration rate
• Low light intensity


  Decreases transpiration rate
• Low temperature


  Decreases transpiration rate
• Wind


  Increases transpiration rate
• High humidity


  Decreases transpiration rate
• Pollution


  Decreases transpiration rate