Auxins — NEET Biology MCQs with Solutions
Free NEET Biology Auxins MCQs with step-by-step solutions (6 questions). Part of Plant Growth and Development. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Auxins · easy · theory
The first plant hormone to be discovered, isolated from oat coleoptile tips, was:
A. Gibberellin
B. Ethylene
C. Cytokinin
D. Auxin ✓ Correct
Solution: Auxin (IAA) was the first hormone discovered, following Darwin and F.W. Went's coleoptile experiments.
Q2 — Auxins · easy · theory
The suppression of the growth of lateral (axillary) buds by the shoot apex is called:
A. Apical dominance ✓ Correct
B. Vernalisation
C. Senescence
D. Abscission
Solution: Auxin produced at the shoot apex inhibits lateral buds — apical dominance (removed by decapitation).
Q3 — Auxins · medium · theory
Auxins are widely used in agriculture/horticulture to:
A. Break seed dormancy
B. Induce cell division only
C. Promote rooting in stem cuttings and prevent fruit/leaf drop ✓ Correct
D. Cause fruit ripening
Solution: Auxins (e.g. IBA, NAA) promote root initiation in cuttings and prevent premature abscission.
Q4 — Auxins · medium · theory
The natural auxin present in plants is:
A. 2,4-D
B. IBA
C. Indole-3-acetic acid (IAA) ✓ Correct
D. NAA
Solution: IAA is the naturally occurring auxin; NAA, 2,4-D and IBA are synthetic auxins.
Q5 — Auxins · hard · theory
The synthetic auxin 2,4-D is used as a ______ because it kills ______ selectively:
A. Fertiliser; monocots
B. Herbicide (weedicide); dicot weeds ✓ Correct
C. Ripening agent; fruits
D. Rooting hormone; all plants
Solution: 2,4-D selectively kills dicotyledonous weeds without harming mature monocots — a common broad-leaf herbicide.
Q6 — Auxins · hard · theory
Auxin promotes cell elongation according to the acid-growth hypothesis by:
A. Preventing water uptake
B. Blocking proton pumps
C. Thickening the cell wall
D. Loosening the cell wall (increasing its extensibility) ✓ Correct
Solution: Auxin activates wall-loosening (acidification via H⁺ pumping), allowing turgor-driven elongation.