Plant Physiology and Growth

C3, C4 or CAM plant?

Aloe vera is a CAM plant. CAM stands for  Crassulacean Acid Metabolism. But what does this mean? I will explain the difference between C3, C4 and CAM plants to you. As can be seen in the name: 

• C3 plants incorporate carbon dioxide into a three-carbon compound. 
• C4 plants incorporate carbon dioxide into a four-carbon compound. 
• CAM plants first store carbon dioxide as an acid. After this, it is used in photosynthesis.  

Another difference is that C3 and C4 plants have open stomata during the day, while for CAM plants it is the opposite. Their stomata open at night. The carbon dioxide is turned into acid before it is stored. During the day, the acid is used for photosynthesis. It is broken down, while the carbon dioxide is released.

C3 plants are most efficient under cool and wet conditions. However, C4 plants and CAM plants are most efficient within dry conditions.

• In C3 plants, photosynthesis happens in the leaf. 
• In C4 plants photosynthesis occurs in the inner cells.
• Finally, CAM plants can go into a stage where the stomata are closed during both day and night. This happens only when extreme weather conditions occur, for example in desserts. The reason for this is to minimize water loss. In figure 5, we are able to see Aloe vera plants in a dessert. 

  

  Figure 5: Aloe vera in dessert