cam pathway


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cam pathway

  1. 1. Crassulacean Acid Metabolism (CAM Pathway) Prepared by Priyanka Khare
  2. 2. Historical Background  CAM was first discovered in the late 1940s. It was observed by the botanists Ranson and Thomas, in the Crassulaceae family of succulents (which includes jade plants and Sedum). Its name refers to acid metabolism in Crassulaceae, not the metabolism of Crassulacean acid.
  3. 3. Identifying a CAM plant  CAM can be considered an adaptation to arid conditions.  CAM plants often display other xerophytic characters, such as thick, reduced leaves with a low surface-area-to-volume ratio; thick cuticle; and stomata sunken into pits. Some shed their leaves during the dry season; others (the succulents) store water in vacuoles.  CAM plants not only are good at retaining water but also use nitrogen very efficiently.
  4. 4.  CAM plants can also be recognized as plants whose leaves have an increasing sour taste during the night yet become sweeter-tasting during the day. This is due to malic acid stored in the vacuoles of the plants' cells during the night and then used up during the day.
  5. 5. Crassulacean acid metabolism (CAM)  Crassulacean acid metabolism, also known as CAM photosynthesis, is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions (drought).  the stomata in the leaves closed during the day to reduce evapotranspiration and but open at night to collect carbon dioxide (CO2).  The CO2 is stored as the four-carbon acid malate, and then react with RuBisco, produce sugar through photosynthesis at day.  Example: cactus, pine apple etc.
  6. 6. Overview of CAM: a two- part cycle
  7. 7. NIGHT PROCESS  When the stomata open, the CO2 is absorb into the cell.  The PEP carboxylase, carbon dioxide in fixing-enzyme react with CO2 to produce malate, the organic acid will stored in vacuole of the cell in low concentration.  The malate will go trough Calvin cycle during the day because the Calvin cycle cannot operate during the night while it still need ATP and NADPH.
  8. 8. DAY PROCESS  During day process, its prevent the loss of water vapour in the plant, the stomata is closed.  Then, the malate is release from the vacuole because high concentration inside and break down into CO2. The CO2 reacts with the RuBP( ribulose bisphosphate) and went trough the standard Calvin cycle. The the sugar were produced
  9. 9. The benefits of CAM  The most important benefit to the plant is the ability to leave most leaf stomata closed during the day.  Being able to keep stomata closed during the hottest and driest part of the day reduces the loss of water through evapotranspiration, allowing CAM plants to grow in environments that would otherwise be far too dry.
  10. 10. o The C4 pathway bears resemblance to CAM; both act to concentrate CO2 around RuBisCO, there by increasing its efficiency. o CAM concentrates it in time, providing CO2 during the day, and not at night, when respiration is the dominant reaction. o C4 plants, in contrast, concentrate CO2 spatiallly, with a RuBisCO reaction centre in a "bundle sheath cell" being inundated with CO2.