CAM Photosynthesis

Definition

CAM (Crassulacean Acid Metabolism) photosynthesis is a specialized photosynthetic pathway used by certain plants to conserve water in arid conditions. During this process, these plants open their stomata at night to absorb carbon dioxide, which is then stored as malate. In the daytime, the stomata close to reduce water loss while the stored malate is converted back to carbon dioxide for use in the Calvin cycle, facilitating photosynthesis even in dry environments.

5 Must Know Facts For Your Next Test

1. CAM photosynthesis is primarily found in succulent plants, such as cacti and some orchids, which are adapted to extremely dry environments.
2. By opening stomata at night instead of during the day, CAM plants significantly reduce water loss through transpiration compared to those that follow the typical C3 pathway.
3. The process involves two main steps: nighttime fixation of CO2 into malate and daytime release of CO2 from malate for the Calvin cycle.
4. Despite being less efficient in carbon fixation compared to C3 photosynthesis, CAM allows plants to thrive in conditions where water is scarce.
5. The ability to switch between CAM and C3 photosynthesis depending on environmental conditions is present in some species, providing flexibility for adaptation.

Review Questions

• How does CAM photosynthesis allow plants to survive in arid environments compared to traditional photosynthetic pathways?
  • CAM photosynthesis enables plants to survive in arid environments by allowing them to open their stomata at night, minimizing water loss while still capturing carbon dioxide. This adaptation lets them store CO2 as malate overnight and use it during the day for photosynthesis without exposing themselves to the harsh conditions of daytime heat and dryness. This method contrasts with traditional pathways where stomata are open during the hotter day, leading to higher water loss.
• Discuss the role of malate in CAM photosynthesis and its importance during both nighttime and daytime processes.
  • Malate plays a critical role in CAM photosynthesis as it serves as a storage form of carbon dioxide captured at night. During the nighttime, CO2 is fixed into malate, which accumulates until daylight. When daytime arrives and the stomata are closed to conserve water, malate is converted back into CO2 for use in the Calvin cycle. This mechanism allows plants to perform photosynthesis efficiently without losing significant amounts of water.
• Evaluate how the ability to switch between CAM and C3 photosynthesis can benefit certain plant species in fluctuating environmental conditions.
  • The ability to switch between CAM and C3 photosynthesis provides significant advantages for certain plant species facing fluctuating environmental conditions. For instance, during periods of drought or high temperatures, switching to CAM allows these plants to conserve water effectively while still carrying out essential photosynthesis. Conversely, when conditions are more favorable with ample water availability, reverting to C3 can maximize carbon fixation efficiency. This flexibility enhances their survival and adaptability in varying climates, giving them a competitive edge over other plant types.

Related terms

Stomata: Small openings on plant leaves that regulate gas exchange and transpiration, playing a crucial role in photosynthesis.

Calvin Cycle: The series of light-independent reactions that take place in the chloroplasts where carbon dioxide is fixed into glucose using energy from ATP and NADPH.

Malate: An intermediate compound in the metabolism of carbohydrates that serves as a storage form of carbon dioxide during CAM photosynthesis.