Question

Which of the following is NOT true about phosphorus nutrition in plant?

• A. Phosphorus is not a constituent of nucleoproteins.
• B. Phosphorus plays important role in transfer of energy in plant.
• C. Large part of phosphorus is absorbed by plants in the form of dihydrogen orthophosphate.
• D. Deficiency symptoms of phosphorus in plants first appear on the older leaves.

Hint:

Remember that phosphorus is a component of "P" in ATP (energy), DNA/RNA (nucleic acids and nucleoproteins), and phospholipids (cell membranes).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Phosphorus is an essential macronutrient that plays a structural and functional role in plant metabolism, energy transfer, and membrane integrity.

Step 2: Detailed Explanation:
Let us analyze each statement to identify the incorrect one:
- Option A: Nucleoproteins are conjugated proteins composed of nucleic acids and proteins.
Since nucleic acids (DNA and RNA) contain a sugar-phosphate backbone, phosphorus is a major, essential constituent of nucleoproteins.
Therefore, the statement "Phosphorus is not a constituent of nucleoproteins" is false.
- Option B: Phosphorus is a constituent of ATP, ADP, and other high-energy phosphate compounds.
It is essential for energy storage and transfer in cellular respiration and photosynthesis. This is correct.
- Option C: Plants absorb phosphorus primarily as orthophosphate ions, specifically dihydrogen orthophosphate ($\text{H}_2\text{PO}_4^-$) in slightly acidic soils, and hydrogen orthophosphate ($\text{HPO}_4^{2-}$) in alkaline soils. This is correct.
- Option D: Like nitrogen, phosphorus is highly mobile in plants.
During deficiency, it is translocated to younger tissues, causing deficiency symptoms (such as dark green or purplish coloration) to appear first on older leaves. This is correct.

Step 3: Final Answer:
The statement "Phosphorus is not a constituent of nucleoproteins" is the incorrect statement.