Why does Photorespiration not occur in CAM Plants?

Why does Photorespiration not occur in CAM Plants?: A CAM (Crassulacean acid metabolism) plant is a type of plant that fixes carbon dioxide through the CAM pathway, which evolved in some plants to adapt to arid conditions. Let’s read why does photorespiration not occur in CAM plants.

What are CAM Plants?

CAM plants, like cacti and succulents, use a different photosynthetic pathway where stomata open at night to uptake carbon dioxide, which is converted to organic acids and stored. Stomata closes during the day to minimize water loss, while organic acid is broken down to release CO₂ for photosynthesis. This adaptation allows CAM plants to conserve water in arid environments and thrive in limited water availability, making them well-suited for desert or arid conditions.

What is Photorespiration?

Photorespiration is a process in plant metabolism that involves the uptake of oxygen and the release of carbon dioxide from organic compounds.  It is the reverse of photosynthesis, which fixes carbon dioxide and releases oxygen. Photorespiration occurs when the enzyme RuBisCO reacts with oxygen instead of carbon dioxide and this can happen on warm, arid days when plants close their stomata to prevent excess water loss.  Photorespiration is harmful to C3 plants because it reduces plant productivity.

Why Does Photorespiration Not Occur in CAM Plants?

Photorespiration is a metabolic process that occurs in plants during photosynthesis, where the Rubisco enzyme binds with oxygen instead of carbon dioxide. This leads to the production of toxic by-products and the wastage of energy. However, CAM plants have developed anatomical and physiological adaptations to avoid photorespiration. The reasons photorespiration does not occur in CAM plants are:

• CAM plants perform carbon fixation at night when stomata are open and minimize water loss. It prevents oxygen uptake, thus avoid photorespiration.
• Carbon dioxide is stored as organic acids during the night and released during the day for photosynthesis. It bypasses the need for the Calvin cycle during daylight.
• CAM plants exhibit control over stomatal openings. It allow them to conserve water during the day while still allowing gas exchange. It reduces the chance of oxygen entering and initiating photorespiration.
• CAM plants have evolved in water-limited environments, where minimizing water loss is important.

CO₂ Uptake in CAM Plants at Night

CO₂ Uptake in CAM Plants at night take place in the following steps:

1. CAM plants open stomata during the night and fiix atmospheric CO₂ using PEP carboxylase enzyme. This enzyme has a higher affinity for CO₂ than oxygen, reducing the chance of photorespiration.
2. CO₂ is fixed and converted into organic acids during the night which is then stored in vacuoles within plant cells until daylight.
3. During the day, organic acids are broken down and releases CO₂ for use in the Calvin cycle of photosynthesis.
4. Stomata remain closed during the day to minimize water loss, preventing both water loss and photorespiration.

CO₂ Release During Daytime

CO₂ release during the day time and photosynthesis in CAM Plants take place in the following steps:

1. Organic acids stored in vacuoles are decarboxylated and releases CO₂.
2. Released CO₂ is utilized in the Calvin cycle to produce sugars and CO₂ fixation occurs via the Calvin-Benson cycle in the chloroplast stroma.
3. ATP and NADPH generated during the light-dependent reactions are used in the Calvin cycle to convert CO₂ into carbohydrates.
4. Stomata remain closed during the day to minimize water loss through transpiration.
5. Photosynthesis occurs during the day when light energy is available. It allow CAM plants to efficiently utilize carbon dioxide for sugar synthesis without photorespiration.

Examples of CAM Plants

Some examples of CAM plants include:

• Cacti
• Quillworts
• Water lobelia
• Tape grass
• Water pygmyweed
• Hydrilla
• Vallisneria

CAM Plants and Use of Water

In CAM plants water is efficiently used in the following way:

• CAM plants shows control over stomatal openings. Stomata open during the night for CO₂ uptake and close during the day to minimize water loss through transpiration.
• CO₂ uptake occurs predominantly at night when temperatures are cooler and atmospheric humidity is higher. It reduces water loss.
• CAM plants store water in their succulent tissues. It allow them to withstand during drought.
• CAM photosynthesis minimizes water loss by fixing CO₂ at night when stomata are open and temperatures are lower. It reduces the need for daytime gas exchange.
• The ability of CAM plants to close stomata during the day while still performing photosynthesis enables them to maintain high water use efficiency. It make them well-adapted to arid and semi-arid environments.

Conclusion – Why does Photorespiration not Occur in CAM Plants?

In conclusion, CAM plants avoid photorespiration by taking in carbon dioxide at night when it’s cooler and storing it for use during the day, bypassing the need for gas exchange when water loss is high. This efficient strategy enables CAM plants to thrive in water-limited environments by conserving water while still performing photosynthesis. Their ability to maximize carbon uptake while minimizing water loss makes CAM photosynthesis advantageous in arid habitats, ensuring their survival and ecological resilience in challenging conditions.

FAQs on Why does Photorespiration not Occur in CAM Plants?

Why Photorespiration Does Not Occur in CAM Plants?

CAM plants avoid photorespiration because they use PEP carboxylase instead of RUBISCO to absorb carbon dioxide. CAM plants open their stomata at night and incorporate CO₂ into organic acids, preventing photorespiration.

Do CAM Plants Use RuBisCO?

Yes, CAM plants use RuBisCO. RuBisCO, or rubisco, is a key enzyme in photosynthesis.

Which Cycle Lacks Photorespiration?

The C4 cycle avoids photorespiration. C4 plants, such as sugarcane, maize, and sorghum, use the PEP enzyme during the first step of carbon fixation to avoid photorespiration.

How is Photorespiration Avoided in CAM Plants?

CAM plants avoid photorespiration by separating initial fixation and the Calvin cycle in space, performing these steps in different cell types. 

Why do CAM Plants Grow Slowly?

CAM plants grow slowly because of their low photosynthetic capacity, which is limited by vacuolar storage capacity and ATP costs.