Question

Before the leaf fall readily mobilized element and not remobilised element respectively are

• A. Nitrogen and Nickel
• B. Sulphur and Calcium
• C. Potassium and Phosphorus
• D. Phosphorus and Calcium

Hint:

Deficiency symptoms of mobile elements first appear in older leaves, while deficiency symptoms of immobile elements such as calcium appear in younger leaves.

Answer 1

The Correct Option is D

Concept: Before senescence and leaf fall, plants remobilize several nutrients from old leaves and transport them to young growing tissues. Elements are classified into:
• Mobile elements
• Immobile elements Mobile nutrients can be transported from older tissues to younger tissues, whereas immobile nutrients remain fixed.

Step 1: Identify mobile nutrients. Highly mobile nutrients include: \[ N,\; P,\; K,\; Mg \] Among these, phosphorus is readily remobilized before leaf abscission.

Step 2: Identify immobile nutrients. Calcium is largely immobile because it becomes incorporated into cell walls and other stable structures. Once deposited, it is not easily transported to other plant parts.

Step 3: Analyze options. Option (A): Nickel is not considered the classic immobile nutrient in this context. Incorrect. Option (B): Sulphur shows limited mobility. Incorrect combination. Option (C): Both phosphorus and potassium are mobile. Incorrect. Option (D): Phosphorus is mobile and calcium is immobile. Correct.

Step 4: Final conclusion. The correct pair is: \[ \boxed{\text{Phosphorus and Calcium}} \] Hence option (D) is correct.