What is the Difference Between C4 and CAM Plants?

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C4 and CAM plants are two types of adaptations that plants have evolved to adapt to hot and dry environments. The primary difference between C4 and CAM plants lies in how they minimize water loss while photosynthesizing.

C4 Plants:

  • C4 plants have evolved to increase the efficiency of photosynthesis by reducing photorespiration, which occurs when RuBisCO, an enzyme responsible for fixing CO2, mistakenly binds with oxygen instead of CO2.
  • C4 plants spatially concentrate CO2 around RuBisCO by using a specialized cell called a bundle sheath cell, which is inundated with CO2.
  • C4 plants release fewer molecules of water per CO2 molecule fixed, making them more water-efficient than C3 plants.

CAM Plants:

  • CAM plants have evolved to fix CO2 at night and store it in the form of malic acid, which is then reduced to malate.
  • During the day, CAM plants release the stored CO2 inside the leaves, allowing carbon fixation to occur by RuBisCO.
  • CAM plants have a different leaf anatomy from C3 plants and fix CO2 at night when their stomata (small pores on the plant's surface) are open, reducing water loss.

In summary, C4 plants concentrate CO2 spatially to reduce photorespiration, while CAM plants temporally separate CO2 fixation and the Calvin cycle to minimize water loss during photosynthesis. Both adaptations allow plants to thrive in hot and dry environments, but they use different mechanisms to achieve this.

Comparative Table: C4 vs CAM Plants

The main differences between C4 and CAM plants are the location of carbon fixation within the plant and the method of handling carbon dioxide. Here is a table of key features of C4 and CAM plants:

Feature C4 Plants CAM Plants
Carbon Fixation Occurs in both mesophyll and bundle sheath cells Occurs only in mesophyll cells
Photorespiration Releases fewer molecules of water per CO2 molecule, reducing water loss Releases more molecules of water per CO2 molecule, increasing water loss
Water Efficiency Higher Lower
Carbon Fixation Product 4-carbon compound Not a 4-carbon compound
Kranz Anatomy Present Absent
Storing Water Cannot store water Can store water
Environmental Adaptation Found in hot, dry environments like deserts Adapted to handle irregular water supply, found in very wet environments

C4 plants have evolved to adapt to dry regions with limited water availability, while CAM plants are more suited for environments with irregular water supply. Both types of plants utilize specific carbon fixation pathways to fix carbon and conserve water, but their mechanisms differ.