transpiration

• transpiration


  = loss of water from the leaves of a plant.
• process of transpiration 


  -leaves have a large surface area to absorb sunlight for photosynthesis

  -covered in a waxy cuticle- makes them waterproof to prevent rapid water loss by evaporation.

  • stomata= co2 and o2 move in and out the leaf by diffusion through microscopic pores in the leaf.
  • stomata open and closed by guard cells.
  • when stomata is opened for gas exchange, water vapour also moves out.
  • stomata open and close to control amount of water lost.
• transpiration stream

  1. water enters roots by osmosis and is transported up the xylem to the leaves. It moves by osmosis across membranes and diffusion across cell walls.
  2. water evaporates freely from permeable cellulose cell walls of the mesophyll cells in leaves into air spaces.
  3. water moves into external air through stomata along diffusion gradient.