Question

Which inorganic form(s) of nitrogen do plants assimilate?
A. Amino acids
B. $NH_{4}^{+}$
C. ${NO_{3}}^{-}$
D. ${NO_{2}}^{-}$
Choose the correct answer from the options given below:

• A. A and C only
• B. B and C only
• C. C and D only
• D. D and A only

Hint:

Plants prefer their inorganic Nitrogen in two flavors: Ammonium ($NH_4^+$) and Nitrate ($NO_3^-$). Everything else is either organic or an intermediate.

Answer 1

The Correct Option is B

Concept: Plants can take up various forms of nitrogen from the soil, but only specific inorganic ions are the primary sources for large-scale assimilation into plant proteins.

Step 1: Identifying Primary Inorganic Forms.
The two main inorganic forms of nitrogen that plants actively uptake and assimilate are Ammonium ($NH_4^+$) (B) and Nitrate ($NO_3^-$) (C).

Step 2: Eliminating Organic and Toxic Forms.
Amino acids (A) are organic forms of nitrogen, not inorganic. While plants can absorb them in small amounts, they are not the "standard" inorganic source. Nitrite ($NO_2^-$) (D) is an intermediate in the soil and is generally toxic to plants if it accumulates; plants typically do not assimilate large amounts of nitrogen directly from the soil in this form.

Step 3: Conclusion.
Therefore, the correct pair of inorganic ions used for plant nitrogen assimilation is $NH_4^+$ and $NO_3^-$, making option (2) the correct choice.