Question

Chlorosis along the leaf margins followed by scorching and browning of tips of older leaves, is a symptom of which essential plant nutrient deficiency?

• A. Nitrogen
• B. Phosphorus
• C. Potassium
• D. Calcium

Hint:

Associate the terms "marginal scorching" or "firing/burning of older leaf tips and margins" directly with Potassium (K) deficiency.
This is one of the most frequently asked diagnostic symptoms in crop nutrition exams.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Essential plant nutrients are classified as mobile or immobile within the plant.
Deficiency symptoms of highly mobile nutrients (like Nitrogen, Phosphorus, and Potassium) appear first on older leaves because the plant translocates these elements to young, developing tissues.

Step 2: Detailed Explanation:
Potassium (K) is a highly mobile nutrient inside plants that regulates stomatal opening, osmotic potential, and enzyme activation.
When potassium is deficient, the plant mobilizes it from older, mature leaves to the younger growing tips.
The characteristic deficiency symptoms of potassium include:
- Marginal chlorosis: Yellowing starts at the leaf margins of the older leaves.
- Leaf scorch: This yellowing is rapidly followed by necrosis, giving the margins and tips a burned, scorched, or brown appearance.
- Curling: The leaf edges may curl upward or downward.
In contrast:
- Nitrogen deficiency causes uniform light green to yellow coloring across the entire older leaf surface (general chlorosis), starting from the tip and moving down the midrib.
- Phosphorus deficiency causes older leaves to turn abnormally dark green or develop a purple/bronze coloration due to anthocyanin accumulation.
- Calcium is highly immobile, and its deficiency symptoms (cup-shaped leaves, hooked tips) appear on young leaves and growing tips.

Step 3: Final Answer:
The described symptom is caused by Potassium deficiency.