What are subsidiary or accessory cells?

Explanation

**Step-by-Step Solution:**

1. **Definition of Stomata**: Stomata are small pore-like structures found on the surface of leaves and stems. They play a crucial role in the processes of transpiration and gas exchange.

2. **Function of Stomata**: The primary functions of stomata include the loss of water vapor (transpiration) and the exchange of gases (such as oxygen and carbon dioxide) between the plant and the atmosphere.

3. **Guard Cells**: Stomata are surrounded by two specialized cells known as guard cells. These cells are responsible for regulating the opening and closing of the stomatal pores based on the plant's needs and environmental conditions.

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