During day time, CAM plants procure carbon dioxide for photosynthesis from

Options

A. pyruvic acid
B. oxaloacetic acid
C. oxalic acid
D. malic acid

Answer

**Step-by-Step Solution:**

1. **Understanding CAM Plants**: CAM (Crassulacean Acid Metabolism) plants have a unique mechanism for photosynthesis that allows them to adapt to arid conditions. They open their stomata at night to take in carbon dioxide (CO2) and close them during the day to minimize water loss.

2. **Nighttime CO2 Fixation**: During the night, CAM plants fix CO2 into organic acids, primarily malic acid, which is stored in vacuoles. This process is crucial because it allows the plant to store carbon for use during the day.

3. **Daytime Stomatal Closure**: During the daytime, the stomata of CAM plants remain closed to prevent water loss. As a result, they cannot directly take in CO2 from the atmosphere.

4. **Conversion of Malic Acid**: In the daytime, the stored malic acid in the vacuoles is converted back into CO2. This conversion is facilitated by specific enzymes that break down malic acid into malate, which then releases CO2.

5. **Utilization of CO2 in Photosynthesis**: The CO2 released from malate is then utilized in the Calvin cycle for photosynthesis, allowing the plant to produce glucose and other carbohydrates.

6. **Conclusion**: Therefore, during the daytime, CAM plants procure carbon dioxide for photosynthesis from malic acid that was stored during the night.

**Final Answer**: During daytime, CAM plants procure carbon dioxide for photosynthesis from malic acid.

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