The .........................pressure of guard cells is responsibel for the opening of stomata.

Explanation

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

1. **Understanding Guard Cells**: Guard cells are specialized cells that surround the stomata (the pores on the leaf surface). They are typically kidney-shaped and play a crucial role in regulating the opening and closing of stomata.

2. **Function of Stomata**: Stomata are responsible for gas exchange and transpiration in plants. They allow water vapor to exit the plant and enable the intake of carbon dioxide necessary for photosynthesis.

3. **Mechanism of Opening Stomata**: The opening of stomata is primarily controlled by the turgidity of the guard cells. When guard cells take up water, they become turgid (swollen), which causes them to bend and open the stomatal pore.

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