Potassium deficiency in plants shows which symptom?

• A. Purplish leaves
• B. Leaf margins scorched/browned
• C. Yellowing older leaves
• D. Leaf curling upward

Answer: (B)

Potassium is a mobile nutrient, so when plants are deficient, symptoms show up first in older leaves as the plant moves potassium to new growth. The most characteristic sign of potassium deficiency is leaf margins scorched or browned, sometimes with brown tips, because the cells at the edges lose function without enough potassium to regulate water and enzyme activity. This margin scorch is the key clue that matches the correct choice.

Other patterns described tend to point to different issues: purplish leaves are more typical of phosphorus-related problems, yellowing of older leaves is often linked to nitrogen deficiency, and leaf curling upward can occur from various stresses but isn’t the hallmark of potassium deficiency.