Which symptom is a clear sign of potassium deficiency in tomato leaves?

• A. Marginal Leaf Scorch and Curling
• B. Pale Yellow Older Leaves
• C. Interveinal Chlorosis
• D. Leaf Burn from Salt Toxicity

Answer: (C)

Potassium deficiency shows up most clearly on the oldest leaves because potassium is mobile in the plant and is moved to new growth when it’s short. The hallmark symptom is marginal scorch and curling: yellowing or pale tissue along the leaf margins with brown, necrotic edges, and often leaves that curl at the tips or edges. This edge scorch is a strong clue that potassium is lacking, since potassium’s role supports water regulation and enzyme activity across the leaf margins.

Other patterns don’t fit potassium deficiency as neatly: pale yellow older leaves are more typical of nitrogen deficiency; interveinal chlorosis (yellowing between veins) points to magnesium or iron deficiencies; and leaf burn from salt toxicity comes from excess salts and tends to show a different, more general burn pattern rather than the distinct marginal scorch seen with potassium deficiency.