In cactus stomata remains open during the night and closed during the day.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question states that in cacti, stomata remain open during the night and closed during the day. We need to determine if this statement is true or false.

2. **Identifying the Plant Type**: Cacti are classified as xerophytic plants, which means they are adapted to survive in extremely dry environments, such as deserts. This adaptation is crucial for their survival in conditions with high temperatures and low water availability.

3. **Function of Stomata**: Stomata are small openings found on the leaves (or green parts) of plants. They play a vital role in gas exchange, allowing carbon dioxide to enter the plant for photosynthesis and oxygen to exit. They also facilitate water vapor loss during transpiration.

4. **Stomatal Behavior in Cacti**: In cacti, stomata are adapted to open at night instead of during the day. This behavior is a strategy to minimize water loss. During the day, when temperatures are high, if the stomata were to remain open, the plant would lose a significant amount of water through transpiration.

5. **CAM Metabolism**: Cacti utilize a specific type of photosynthesis known as Crassulacean Acid Metabolism (CAM). This process allows them to fix carbon dioxide at night when temperatures are cooler and humidity is higher, thereby reducing water loss. The carbon dioxide is stored in the form of organic acids and is used during the day for photosynthesis when the stomata are closed.

6. **Conclusion**: Since cacti do indeed open their stomata at night and close them during the day to conserve water, the statement in the question is true.

**Final Answer**: True, in cacti, stomata remain open during the night and closed during the day.

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