transport in plants

• the epidermis…

  covers the outer surfaces of the plant for protection
• the palisade mesophyll…

  is the main site of photosynthesis in the leaf
• the spongy mesophyll…

  is the air spaces between cells that allow gases to diffuse through the leaf
• the xylem vessels…

  • transport water and minerals through the plant
  • support the plant
• the phloem vessels…

  transport dissolved food materials through the plant
• the meristem tissue…

  • is found mainly at the tips of the roots and shoots
  • produces new cells for growth
• The leaf is…

  a plant organ
• water and minerals are..

  transported up by xylem vessels
• the loss of water from the leaves is called..

  transpiration
• factors that affect the rate of transpiration

  • increased temperature - increase
  • faster air flow - increase
  • increased light intensity - increase
  • increase in humidity - decrease
• an increase in temperature will…

  • increase the rate
  • more energy is transferred to the water to allow it to evaporate
• faster air flow will..

  • increase the rate
  • blows away water vapour allowing more evaporation to occur
• increased light intensity will…

  • increase the rate
  • causes the stomata to open
• increase in humidity will…

  • decrease the rate
  • air contains more water vapour, concentration gradient for diffusion is lower
• what is the role of guard cells

  • to open and close stomata
• At night the stomata are…

  • closed
  • why? - carbon dioxide isnt needed for photosynthesis so closing the stomata reduces water loss
• when water is plentiful guard cells…

  • take up water to bend
  • this causes the stomata to open so gases for photosynthesis are free to move in and out of the stomata
• when water is scarce…

  • losing water makes the stomata change shape and it closes
  • this stops the plant from losing water through transpiration
• translocation

  • movement of food through phloem
  • eg. phloem transports dissolved sugars from the leaves to the rest of the plant