In land plants guard cells differ from other epidermal cells in the possession of .........

Explanation

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

1. **Understanding Epidermal Tissue System**: The epidermal tissue system forms the outermost covering of the plant body. It is primarily a single layer of cells that provides protection to the plant.

2. **Presence of Stomata**: In land plants, the epidermis of aerial parts (like leaves and stems) contains minute pores called stomata, which are essential for gas exchange. Stomata are absent in roots.

3. **Function of Stomata**: Stomata facilitate gaseous exchange during respiration and photosynthesis. They allow the intake of carbon dioxide and the release of oxygen during photosynthesis, and they also play a role in transpiration, which is the release of excess water vapor.

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