Phosphorus (P) is an important essential nutrient.
(A) Plant roots absorb P in the \(H_2PO_4^-\) form, but under neutral to alkaline environments, \(HPO_4^{2-}\) and or \(PO_4^{3-}\) ions could also be taken up.
(B) In normal P-sufficient plants, P-content varies from 0.1% to 0.4% by weight.
(C) It is an essential ingredient for Rhizobium bacteria to convert atmospheric N (\(N_2\)) into the ammonium (\(NH_4\)) form usable by plant.
(D) Because of being immobile in plants, first signs of its deficiency appear on the older leaves.
Choose the correct answer from the options given below:

Question

Which of the following statements is false?

Answer 1

We are given four statements about phosphorus nutrition and need to sort out which ones are actually correct.

(A), on uptake forms: true. Roots mostly take up phosphorus as \(H_2PO_4^-\) in acidic to neutral soil, but as the soil turns more alkaline, the forms \(HPO_4^{2-}\) and \(PO_4^{3-}\) become more available and are absorbed as well.
(B), on tissue content: true. A healthy plant with enough phosphorus normally carries about 0.1% to 0.4% P by dry weight, which is the standard sufficiency range used in plant analysis.
(C), on nitrogen fixation: true. The nitrogenase enzyme in Rhizobium nodules needs a large, steady flow of ATP to split the tough triple bond of atmospheric \(N_2\) and turn it into ammonium, and phosphorus is what ATP is built from, so it is essential fuel for this reaction.
(D), on deficiency location: false. The statement blames immobility, but phosphorus is actually a mobile element inside the plant. Because it is mobile, older leaves give up their phosphorus to younger growth when supply is tight, which is exactly why deficiency shows on the older leaves, not because the nutrient cannot move.

Only statement (D) breaks down, and it breaks down specifically because it mislabels phosphorus as immobile when it is mobile, so the three sound statements are (A), (B) and (C).

Let's summarize:

Phosphorus uptake form shifts with soil pH, and normal tissue phosphorus sits around 0.1 to 0.4 percent.
Phosphorus fuels nitrogen fixation through ATP, and it is a mobile nutrient, so its deficiency shows on old leaves for the opposite reason stated in (D).

So the correct combination is (A), (B) and (C) only, option 1.

Answer 2

We are given four statements about phosphorus nutrition and need to sort out which ones are actually correct.

(A), on uptake forms: true. Roots mostly take up phosphorus as \(H_2PO_4^-\) in acidic to neutral soil, but as the soil turns more alkaline, the forms \(HPO_4^{2-}\) and \(PO_4^{3-}\) become more available and are absorbed as well.
(B), on tissue content: true. A healthy plant with enough phosphorus normally carries about 0.1% to 0.4% P by dry weight, which is the standard sufficiency range used in plant analysis.
(C), on nitrogen fixation: true. The nitrogenase enzyme in Rhizobium nodules needs a large, steady flow of ATP to split the tough triple bond of atmospheric \(N_2\) and turn it into ammonium, and phosphorus is what ATP is built from, so it is essential fuel for this reaction.
(D), on deficiency location: false. The statement blames immobility, but phosphorus is actually a mobile element inside the plant. Because it is mobile, older leaves give up their phosphorus to younger growth when supply is tight, which is exactly why deficiency shows on the older leaves, not because the nutrient cannot move.

Only statement (D) breaks down, and it breaks down specifically because it mislabels phosphorus as immobile when it is mobile, so the three sound statements are (A), (B) and (C).

Let's summarize:

Phosphorus uptake form shifts with soil pH, and normal tissue phosphorus sits around 0.1 to 0.4 percent.
Phosphorus fuels nitrogen fixation through ATP, and it is a mobile nutrient, so its deficiency shows on old leaves for the opposite reason stated in (D).

So the correct combination is (A), (B) and (C) only, option 1.

Show Hint

The Correct Option is A

Solution and Explanation

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