The stomata of most plants …………………..... in the evening and .................. in the morning.

Explanation

**Step-by-Step Solution:**

1. **Understanding Stomata:** Stomata are small openings found on the surface of leaves that allow for gas exchange. They play a crucial role in the process of photosynthesis and transpiration.

2. **Role of Guard Cells:** Each stoma is surrounded by two guard cells that regulate its opening and closing. The guard cells control the size of the stomatal pore based on environmental conditions and the plant's needs.

3. **Stomatal Behavior:** The opening and closing of stomata are influenced by various factors, including light, humidity, and carbon dioxide concentration. Generally, stomata open during the day when there is sunlight for photosynthesis and close at night to conserve water.

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