Q.66 Nitrogen, the main element contributing to the growth of plants in vitro and in-vivo is the constituent of
A. Amino acids
B. Certain hormones
C. Co-factor of many enzymes
D. Chlorophyll
E. In storage and transfer of energy in plants
Choose the most appropriate answer from the options given below:
(A) A, B and C only
(B) A, B and D only
(C) B, C and D only
(D) C, D, E only
The correct answer is (A) A, B, and C only.
Detailed Analysis of Options
Nitrogen is essential for plant growth in vitro and in vivo, forming key biomolecules. Here’s each component:
A. Amino acids: True—N is in amine groups; proteins (20% N by weight) drive growth.
B. Certain hormones: True—cytokinins (zeatin), some auxins contain N in purine rings.
C. Co-factor of many enzymes: True—N in heme (cytochromes), biotin, ATP, enzyme activation.
D. Chlorophyll: False—Mg-central, N in porphyrin ring but not defining constituent (question implies primary role).
E. Storage/transfer of energy: False—C, H, O, P (ATP); N absent from carbohydrates, lipids.
Option Breakdown
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(A) A,B,C only: Correct—matches nitrogen’s biochemical roles precisely.
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(B) A,B,D only: Wrong—D is magnesium-based.
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(C) B,C,D only: Wrong—excludes amino acids (primary N sink).
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(D) C,D,E only: Wrong—D/E incorrect; misses amino acids.
Introduction: Nitrogen Role in Plant Growth
Nitrogen, the main element for plant growth in vitro and in vivo, constitutes amino acids, certain hormones, and enzyme co-factors—driving protein synthesis, cell division, and metabolism. Deficiency causes chlorosis; excess delays flowering. Essential for NEET MCQs testing A-E options on nitrogen functions.
Nitrogen’s Biochemical Roles
Primary functions:
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Amino acids (A): N in -NH₂ groups; 16% plant dry weight as protein.
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Hormones (B): Cytokinins (N6-substituted adenines), IAA derivatives contain N.
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Enzyme co-factors (C): Heme (cytochromes), FAD, NAD+, biotin all nitrogenous.
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NOT chlorophyll (D): Mg²⁺ at center; N peripheral in pyrroles.
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NOT energy storage (E): ATP (adenine N), but energy from C-H bonds.
MCQ Solution: Nitrogen Constituent Roles A B C D E
Question: Nitrogen constitutes: A. amino acids B. hormones C. co-factors D. chlorophyll E. energy storage/transfer.
| Option | Evaluation |
|---|---|
| (A) A,B,C only | Correct—precise nitrogen roles |
| (B) A,B,D only | Wrong—chlorophyll = Mg |
| (C) B,C,D only | Misses amino acids (main N sink) |
| (D) C,D,E only | Wrong—D/E false |
Answer: (A)
Practical Implications
In vitro: MS medium: 60 mg/L NH₄⁺ + 250 mg/L NO₃⁻ for optimal callus/shoot growth.
In vivo: Urea (46% N) boosts vegetative growth but risks leaching. N-demand peaks at tillering.
Deficiency signs: Older leaves yellow (mobile nutrient remobilized).
Exam Strategy
chlorophyll = magnesium as classic distractor. Amino acids always primary nitrogen role. Cytokinins confirm B.
