12 photosynthesis - part 09 - CAM-Crassulacean Acid Metabolism

 

12 photosynthesis - part 09 - CAM-Crassulacean Acid Metabolism


CAM-Crassulacean Acid Metabolism:


  • It is one more alternative pathway of carbon fixation found in desert plants. 
  • It was first reported in the family Crassulaceae, so called as CAM (Crassulacean Acid Metabolism).
  • In CAM plants, stomata are scotoactive i.e. active during night, so initial CO2 fixation occurs in night.
  • Thus C4 pathway fix CO2 at night and reduce CO2 in day time via the C3 pathway by using NADPH formed during the day. 
  • PEP caboxylase and Rubisco are present in the mesophyll cell (no Kranz anatomy).
  • Formation of malic acid during dark is called acidification (phase I).
  • Malate is stored in vacuoles during the night.
  •  Malate releases CO2 during the day for C3 pathway within the same cell is called deacidification (phase II).
  • Examples of CAM plants : Kalanchoe, Opuntia, Aloe etc. 
  • The Chemical reactions of the carbon di-oxide fixation and its assimilation are similar to that of C4 plants.

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