Question

According to Bray's Nutrient Mobility concept, which among following element is mobile in plants but immobile in soil?

• A. Nitrogen
• B. Phosphorus
• C. Boron
• D. Zinc

Hint:

Remember that mobile nutrients in plants show deficiency symptoms first on older leaves (like Phosphorus and Nitrogen), whereas immobile nutrients show symptoms first on younger leaves.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Roger H. Bray developed the nutrient mobility concept, which classifies essential plant nutrients based on their relative movement within the soil profile and their internal translocation within the plant tissue.

Step 2: Detailed Explanation:
Nutrients like nitrogen (mainly as nitrate, \(\text{NO}_3^-\)) and boron (as boric acid, \(\text{H}_3\text{BO}_3\)) are highly mobile in both the soil and the plant.
Zinc is highly immobile in both the soil and within the plant.
Phosphorus (primarily as orthophosphate ions, \(\text{H}_2\text{PO}_4^-\) and \(\text{HPO}_4^{2-}\)) is highly mobile within the plant, meaning it easily translocates from older leaves to growing points during deficiency.
However, phosphorus is highly immobile in soil because it readily undergoes chemical precipitation and adsorption reactions with iron, aluminum, and calcium compounds.

Step 3: Final Answer:
Therefore, phosphorus is the nutrient that is mobile in plants but immobile in soil.