The role of water

• In photosystem two, there is an enzyme that when in the presence of light will split molecules fo water to produce protons, electrons and oxygen.
• Some of the oxygen produced in photolysis is used by plant cells for aerobic respiration, but during periods of high light intensity, the rate of photosynthesis is greater than the rate of respiration in the plant, so much so that the oxygen by-product will diffuse out of the leaves via the stomata into the atmosphere
• Water:

  • Is the source of protons that is used for photophosphorylation
  • donates electrons to chlorophyll to replace the electrons that are lost when light strikes chlorophyll
  • water is the source of oxygen
  • water keeps plant cells turgid so that they can function