Who propsed `K^(+)` ion hypthesis of stomatal opening and closure ?

Explanation

**Step-by-Step Solution:**

1. **Identify the Hypothesis**: The question asks about the potassium ion hypothesis related to stomatal opening and closure.

2. **Recall the Scientist**: The potassium ion hypothesis was proposed by a scientist named Levitt.

3. **Understand the Mechanism**: According to Levitt's hypothesis, the opening and closing of stomata depend on the potassium ion (K⁺) gradient in the guard cells.

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