Question

Mineral elements are classified on the basis of their movement within a plant and their affinity to retranslocate during deficiencies. Highly immobile element in plant system is:

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

Hint:

Mobile = N, P, K, Mg (Symptoms in old leaves).
Immobile = Ca, S, Fe, B (Symptoms in young leaves).
Calcium is "stuck" in the cell wall glue (middle lamella).

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question focuses on the mobility of minerals within a plant. When a soil is deficient in an element, mobile elements move from old leaves to young ones, while immobile elements stay locked in older tissues.
Detailed Explanation:

• Mobile Elements:
Elements like Nitrogen, Phosphorus, and Potassium (NPK) are highly mobile.
Plants can easily relocate these from older, senescing leaves to the younger, growing tips.
Therefore, deficiency symptoms for these appear first in older leaves.

• Immobile Elements:
Calcium is a structural component of the plant cell wall (it forms calcium pectate in the middle lamella).
Once deposited, it cannot be solubilized and retranslocated through the phloem to other parts of the plant.
Therefore, when the soil is deficient in Calcium, the plant cannot move it to the new growing tips, and deficiency symptoms (like "tip hook" or necrosis) appear first in younger leaves.

• Other Elements:
Sulfur, Iron, and Boron are also considered relatively immobile compared to NPK.

Step 2: Final Answer:
Calcium is the classic example of a highly immobile mineral element in the plant system.