Question

Identify the sequence of nutrient elements in crops, capable of getting re-distributed under deficiency conditions in ascending order: [Question ID = 703][Question Description = 203_34_PLB_AUG22_Q103]

• A. N < Fe < B [Option ID = 2809]
• B. K < Mn < Ca [Option ID = 2810]
• C. P < Mg < B [Option ID = 2811]
• D. B < Fe < N [Option ID = 2812]

Hint:

Mobile Elements (symptoms on old leaves): N, P, K, Mg, Mo.
Immobile Elements (symptoms on young leaves/buds): Ca, B, Fe, Mn, Cu, S.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Nutrient mobility within the plant determines where deficiency symptoms first appear and how effectively an element can be re-translocated from older tissues to actively growing sinks (like young leaves or fruits). Elements are classified as mobile, partially mobile, or immobile. Ascending order of redistribution capability means moving from the least mobile (immobile) to the most mobile elements.

Step 2: Detailed Explanation:
Let's analyze the redistribution capacity of the elements in Option D:
1. Boron (B): Boron is considered highly immobile in the phloem of most plant species. Once it is incorporated into the cell wall structure or stored in tissues, it cannot be easily redistributed. Consequently, deficiency symptoms appear first at the growing tips (apical meristems). Thus, it has the lowest redistribution capacity.
2. Iron (Fe): Iron is generally considered immobile or only slightly mobile. While it is not as strictly locked as Boron or Calcium, its redistribution from older leaves to younger ones is very limited, which is why young leaves show interveinal chlorosis during deficiency. It occupies an intermediate position in this list.
3. Nitrogen (N): Nitrogen is highly mobile in the plant. When soil nitrogen is scarce, the plant readily degrades proteins in older leaves and transports the resulting amino acids to younger, developing parts. This is why nitrogen deficiency symptoms (yellowing) appear first on older, lower leaves. It has the highest redistribution capacity.
Therefore, the sequence B (Immobile) < Fe (Less mobile) < N (Highly mobile) correctly follows the ascending order of redistribution capability.

Step 3: Final Answer:
The ascending sequence for redistribution is B < Fe < N.