Which of the following statement is true about Stomata of plants in crassulaceae

Options

A. are always open
B. Open during the day and close at night
C. Open during the night and close during the day
D. Never open

Answer

**Step-by-Step Text Solution:**

1. **Understanding Crassulaceae Plants**:
- Crassulaceae is a family of plants that includes succulents like cacti and euphorbias, which are adapted to dry habitats (xeric conditions).

2. **Stomatal Behavior**:
- In Crassulaceae plants, a special photosynthetic pathway known as Crassulacean Acid Metabolism (CAM) is utilized. This adaptation helps these plants conserve water.

3. **Stomata Opening and Closing**:
- During the night, the stomata of these plants open, allowing carbon dioxide (CO2) to enter. This is crucial because it helps in the fixation of carbon during the cooler night hours when water loss through transpiration is minimized.

4. **Carbon Dioxide Fixation**:
- The enzyme PEP carboxylase plays a key role in this process. It helps in fixing the absorbed CO2 with phosphoenolpyruvate (PEP) to form malic acid, which is stored in the vacuoles of the cells.

5. **Daytime Process**:
- During the day, the stomata remain closed to prevent water loss. The stored malic acid is then decarboxylated (removal of CO2) to release CO2 for the Calvin cycle, which occurs in the presence of light.

6. **Photosynthesis**:
- The released CO2 is fixed in the Calvin cycle using ribulose bisphosphate (RuBP), allowing the plant to perform photosynthesis while minimizing water loss.

7. **Conclusion**:
- Therefore, the true statement about the stomata of plants in Crassulaceae is that they open at night and close during the day, which is characteristic of CAM plants.

**Final Answer**: The stomata of plants in Crassulaceae open at night and close during the day.

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