Potassium (K) is a mobile nutrient in plants. Deficiency symptoms typically appear first in older leaves because the plant translocates potassium to younger, growing tissues. Common symptoms of potassium deficiency include chlorosis (yellowing) along the margins and tips of older leaves, which progresses inwards. As the deficiency worsens, these yellow areas often develop into necrotic spots (dead tissue), giving the appearance of scorched or brown margins and tips.