The hormones which help in the intake of `K^(+)` ions by guard cells and hence speed up the opening of stomata are

Options

A. cytokinins
B. auxins
C. gibberellins
D. ethylene

Answer

**Step-by-Step Solution:**

1. **Understanding Guard Cells**: Guard cells are specialized cells located in the leaf epidermis that surround the stomatal pores. Their primary function is to regulate the opening and closing of these pores, which allows for gas exchange (like CO2 intake) and regulates water loss through transpiration.

2. **Role of Potassium Ions (K⁺)**: The opening of stomata is closely linked to the movement of potassium ions (K⁺) into the guard cells. When K⁺ ions enter the guard cells, they cause the cells to become turgid (swollen with water), leading to the opening of the stomatal pores.

3. **Hormonal Regulation**: Various plant hormones influence the movement of K⁺ ions into guard cells. The question asks which hormones specifically aid in this process.

4. **Identifying the Correct Hormone**: Among the hormones listed (cytokinins, auxins, gibberellins, and ethylene), cytokinins are known to promote the uptake of K⁺ ions in guard cells, thereby facilitating the opening of stomata.

5. **Conclusion**: Therefore, the hormone that helps in the intake of K⁺ ions by guard cells and speeds up the opening of stomata is **cytokinins**.

**Final Answer**: Cytokinins.

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