A plant requires potassium mainly for?

Explanation

**Step-by-Step Solution:**

1. **Understanding the Role of Potassium in Plants:**
- Potassium is an essential macronutrient for plants, playing a critical role in various physiological processes.

2. **Key Functions of Potassium:**
- **Regulation of Stomatal Opening:**
- Potassium ions help in the opening and closing of stomata, which are small pores on the leaf surface. This regulation is crucial for gas exchange, particularly the uptake of carbon dioxide (CO2) during photosynthesis.
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