Explain How and Why Cacti Perform Cam Photosynthesis.

Explain How and Why Cacti Perform Cam Photosynthesis

Cacti are unique and fascinating plants that have evolved to thrive in some of the harshest environments on Earth, such as deserts. One of the key adaptations that have allowed cacti to survive in these arid conditions is their ability to perform Crassulacean Acid Metabolism (CAM) photosynthesis. CAM photosynthesis is a specialized form of photosynthesis that enables plants to conserve water while still producing energy.

To understand how and why cacti perform CAM photosynthesis, let’s delve into the process and its benefits:

The Process of CAM Photosynthesis:
1. Stomata Closure: During the day, when temperatures are high and water availability is limited, cacti keep their stomata, small openings on their surface, tightly closed to minimize water loss through transpiration.
2. Nighttime CO2 Uptake: Instead of absorbing carbon dioxide (CO2) during the day like most plants, cacti open their stomata at night to take in CO2. This allows them to avoid excessive water loss through evaporation.
3. Storage of CO2: Once inside the plant, the CO2 molecules are converted into organic acids, primarily malic acid, which are stored in vacuoles within the cells.
4. Daytime CO2 Release: During the day, when temperatures are lower, cacti close their stomata to prevent water loss. However, they can still perform photosynthesis by breaking down the stored organic acids into CO2, which is then used in the Calvin cycle to produce glucose and other carbohydrates.

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The Benefits of CAM Photosynthesis for Cacti:
1. Water Conservation: By only opening their stomata at night, cacti reduce water loss through evaporation. This adaptation is crucial for survival in arid environments where water is scarce.
2. Temperature Regulation: Closing their stomata during the day also helps cacti to regulate internal temperatures. By preventing hot air from entering the plant, they minimize the risk of overheating.
3. Efficient Use of CO2: By storing CO2 as organic acids at night and releasing it during the day, cacti can maximize their use of this essential gas for photosynthesis.
4. Adaptation to Harsh Environments: CAM photosynthesis is an energy-efficient strategy that allows cacti to survive in habitats with intense sunlight, high temperatures, and low water availability.
5. Increased Drought Tolerance: CAM photosynthesis helps cacti withstand prolonged periods of drought by reducing water loss and maintaining essential metabolic processes.


1. Why do cacti perform CAM photosynthesis?
Cacti perform CAM photosynthesis to conserve water in their arid habitats and maximize their ability to produce energy.

2. How do cacti store CO2 during CAM photosynthesis?
Cacti convert CO2 into organic acids, primarily malic acid, which are stored in vacuoles within their cells.

3. What is the advantage of opening stomata at night?
Opening stomata at night allows cacti to take in CO2 without losing excessive amounts of water through transpiration.

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4. How do cacti regulate their internal temperature?
By closing their stomata during the day, cacti prevent hot air from entering the plant, helping to regulate internal temperatures.

5. Can all plants perform CAM photosynthesis?
No, CAM photosynthesis is a specialized adaptation found in certain plants, including cacti, orchids, and some bromeliads.

6. Are there any disadvantages to CAM photosynthesis?
While CAM photosynthesis is highly beneficial for cacti in arid environments, it can limit their growth rate compared to plants that perform standard C3 photosynthesis.

7. Can cacti switch between CAM and C3 photosynthesis?
Under certain conditions, such as when water availability increases, cacti can switch to C3 photosynthesis temporarily. However, CAM photosynthesis remains their primary mode of photosynthesis.

In conclusion, CAM photosynthesis is a remarkable adaptation that allows cacti to survive and thrive in harsh desert environments. By conserving water, regulating temperature, and efficiently using CO2, cacti have developed a unique strategy to maximize their chances of survival in arid conditions.