Introduction to plant growth regulators MCQs With Answer

Introduction to plant growth regulators MCQs With Answer provides B.Pharm students a concise, keyword-rich overview of plant growth regulators (PGRs) and their pharmaceutical relevance. This guide covers major plant hormones—auxins, gibberellins, cytokinins, ethylene, abscisic acid, brassinosteroids—and synthetic regulators, their biosynthesis, modes of action, transport, and analytical assays such as HPLC and GC-MS. Emphasis is placed on applications in micropropagation, elicitation of secondary metabolites for drug production, formulation, quality control, and safety. These MCQs reinforce core concepts, experimental techniques, and regulatory considerations essential for pharmacy graduates working with plant-derived therapeutics. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the primary natural auxin involved in cell elongation and apical dominance?

• Indole-3-acetic acid (IAA)
• Gibberellic acid (GA3)
• Kinetin
• Abscisic acid (ABA)

Correct Answer: Indole-3-acetic acid (IAA)

Q2. Which plant growth regulator is most directly associated with seed dormancy and drought response?

• Ethylene
• Abscisic acid (ABA)
• Cytokinin
• Auxin

Correct Answer: Abscisic acid (ABA)

Q3. Which assay technique is commonly used for quantifying low levels of gibberellins in plant extracts?

• Thin layer chromatography (TLC)
• High performance liquid chromatography (HPLC) coupled with MS
• Colorimetric IAA bioassay
• Paper chromatography

Correct Answer: High performance liquid chromatography (HPLC) coupled with MS

Q4. Cytokinins primarily promote which of the following cellular processes?

• Stem elongation
• Cell division and shoot initiation
• Stomatal closure
• Leaf abscission

Correct Answer: Cell division and shoot initiation

Q5. Which compound is a synthetic auxin used as a herbicide at high concentrations?

• 2,4-D (2,4-dichlorophenoxyacetic acid)
• Zeatin
• Brassinolide
• Paclobutrazol

Correct Answer: 2,4-D (2,4-dichlorophenoxyacetic acid)

Q6. Ethylene is synthesized from which amino acid precursor in plants?

• Tryptophan
• Methionine
• Phenylalanine
• Tyrosine

Correct Answer: Methionine

Q7. Which PGR class is most important for promoting stem elongation and breaking seed dormancy in many species?

• Gibberellins
• Auxins
• Cytokinins
• Abscisic acid

Correct Answer: Gibberellins

Q8. In plant tissue culture, a high cytokinin to auxin ratio typically induces:

• Root formation
• Shoot formation and shoot proliferation
• Callus browning
• Somatic embryo maturation

Correct Answer: Shoot formation and shoot proliferation

Q9. Which analytical method allows spatial localization of PGRs within tissues using antibodies?

• ELISA (enzyme-linked immunosorbent assay)
• Immunolocalization (immunohistochemistry)
• Gas chromatography
• Bioautography

Correct Answer: Immunolocalization (immunohistochemistry)

Q10. Which plant hormone acts as a gaseous signaling molecule and ripening promoter?

• Auxin
• Ethylene
• Gibberellin
• Brassinosteroid

Correct Answer: Ethylene

Q11. Brassinosteroids are primarily known for regulating:

• Seed dormancy
• Cell elongation, vascular differentiation, and stress tolerance
• ABA synthesis inhibition
• Protein degradation

Correct Answer: Cell elongation, vascular differentiation, and stress tolerance

Q12. Which PGR is commonly used to prevent pre-harvest fruit drop in commercial orchards?

• Cytokinin
• Ethephon (ethylene releaser)
• Auxin analogs
• Paclobutrazol

Correct Answer: Ethephon (ethylene releaser)

Q13. Paclobutrazol is classified as a:

• Gibberellin biosynthesis inhibitor
• Cytokinin agonist
• Auxin transport facilitator
• Ethylene precursor

Correct Answer: Gibberellin biosynthesis inhibitor

Q14. Which technique best separates volatile plant hormones like ethylene for measurement?

• Gas chromatography (GC)
• Size-exclusion chromatography
• Paper chromatography
• Ion exchange chromatography

Correct Answer: Gas chromatography (GC)

Q15. Which hormone interaction commonly promotes lateral root formation when auxin and cytokinin balance shifts?

• High auxin to cytokinin ratio
• High cytokinin to auxin ratio
• High ABA to GA ratio
• High ethylene to auxin ratio

Correct Answer: High auxin to cytokinin ratio

Q16. Which plant hormone is central to systemic acquired resistance and defense signaling?

• Salicylic acid (SA)
• Auxin
• Gibberellin
• Ethylene

Correct Answer: Salicylic acid (SA)

Q17. Which bioassay uses Avena coleoptile elongation to estimate auxin activity?

• Root inhibition assay
• Avena coleoptile elongation bioassay
• Letrozole assay
• Leaf disc senescence assay

Correct Answer: Avena coleoptile elongation bioassay

Q18. Which PGR promotes cell expansion by loosening cell walls via activation of expansins?

• Cytokinin
• Auxin
• ABA
• Ethylene

Correct Answer: Auxin

Q19. Which of the following is a major commercial cytokinin used in micropropagation?

• Kinetin and benzylaminopurine (BAP)
• Indole-3-butyric acid (IBA)
• Gibberellic acid (GA3)
• Abscisic acid (ABA)

Correct Answer: Kinetin and benzylaminopurine (BAP)

Q20. What is a primary pharmaceutical interest in manipulating PGRs in plant cell cultures?

• Increasing cellulose content only
• Enhancing production of secondary metabolites and pharmaceutically active compounds
• Reducing protein synthesis
• Accelerating seed dormancy

Correct Answer: Enhancing production of secondary metabolites and pharmaceutically active compounds

Q21. Which molecular receptor family perceives auxin in the nucleus to regulate transcription?

• TIR1/AFB F-box receptors
• G-protein coupled receptors
• Histidine kinases
• Leucine-rich repeat receptor kinases

Correct Answer: TIR1/AFB F-box receptors

Q22. Which method is most appropriate for quantifying abscisic acid levels in plant tissues for pharmacognosy studies?

• Polarimetry
• HPLC-MS/MS with appropriate sample cleanup
• Simple UV spectrophotometry without extraction
• Folin-Ciocalteu reagent assay

Correct Answer: HPLC-MS/MS with appropriate sample cleanup

Q23. Jasmonates (JA) are primarily involved in which plant process relevant to pharmaceutical compound production?

• Photosynthesis regulation only
• Defense responses and induction of secondary metabolite biosynthesis
• Seed coat formation
• Leaf abscission exclusively

Correct Answer: Defense responses and induction of secondary metabolite biosynthesis

Q24. Which compound acts as an ethylene-releasing PGR used to induce ripening?

• Paclobutrazol
• Ethephon (2-chloroethylphosphonic acid)
• BA (benzyladenine)
• 2,4-D

Correct Answer: Ethephon (2-chloroethylphosphonic acid)

Q25. Which analytical approach helps detect PGR residues in herbal drug preparations to ensure safety?

• Organoleptic testing
• GC-MS or LC-MS residue analysis
• Simple pH measurement
• Moisture content determination only

Correct Answer: GC-MS or LC-MS residue analysis

Q26. What is the usual effect of abscisic acid on stomatal aperture?

• Stomatal opening by increasing turgor
• Stomatal closure to reduce water loss
• No effect on stomata
• Permanent stomatal differentiation

Correct Answer: Stomatal closure to reduce water loss

Q27. Which PGR is commonly applied to increase root initiation in cuttings?

• Indole-3-butyric acid (IBA)
• Gibberellic acid (GA3)
• Cytokinin (BAP)
• Abscisic acid (ABA)

Correct Answer: Indole-3-butyric acid (IBA)

Q28. Which statement best describes auxin polar transport?

• Auxin diffuses randomly between cells
• Auxin is transported directionally via PIN efflux carriers and AUX/LAX influx carriers
• Auxin is immobile in plant tissues
• Auxin transport is ATP-independent and unregulated

Correct Answer: Auxin is transported directionally via PIN efflux carriers and AUX/LAX influx carriers

Q29. Which PGR would you use to break bud dormancy and encourage sprouting in horticulture?

• Abscisic acid (ABA)
• Gibberellins or cytokinins depending on species
• Ethylene inhibitor only
• Brassinosteroid inhibitor

Correct Answer: Gibberellins or cytokinins depending on species

Q30. Which natural compound is a major precursor for many brassinosteroids?

• Squalene and sterol biosynthetic intermediates
• Tryptophan
• Acetyl-CoA only
• Glucose

Correct Answer: Squalene and sterol biosynthetic intermediates

Q31. Which of the following describes an antagonistic interaction between PGRs?

• Auxin and cytokinin always act synergistically
• Abscisic acid inhibiting gibberellin-induced germination
• Gibberellin blocking all cytokinin effects
• Ethylene promoting GA biosynthesis directly

Correct Answer: Abscisic acid inhibiting gibberellin-induced germination

Q32. For quality control in herbal formulations, which parameter related to PGRs is essential to test?

• PGR residue levels and stability under storage conditions
• Only microbial load
• Only moisture content
• Color intensity only

Correct Answer: PGR residue levels and stability under storage conditions

Q33. Which signaling molecule is synthesized from linolenic acid and influences defense and secondary metabolism?

• Jasmonic acid (JA)
• Auxin
• Brassinosteroid
• Gibberellin

Correct Answer: Jasmonic acid (JA)

Q34. What is the primary goal of using PGRs as elicitors in cell cultures for drug production?

• To increase primary metabolite sugar levels
• To stimulate biosynthetic pathways that increase secondary metabolite yield
• To sterilize cultures
• To induce mutations

Correct Answer: To stimulate biosynthetic pathways that increase secondary metabolite yield

Q35. Which PGR is often monitored because it can accelerate fruit ripening and cause spoilage during storage?

• Gibberellin
• Ethylene
• Auxin
• Abscisic acid

Correct Answer: Ethylene

Q36. Which method is suitable for tracing PGR transport pathways using high sensitivity?

• Radiolabeled tracer studies with autoradiography
• Visual observation only
• Simple titration
• Dry weight measurement

Correct Answer: Radiolabeled tracer studies with autoradiography

Q37. Which of the following is a common side-effect of overapplication of auxins in crop or medicinal plant production?

• Enhanced secondary metabolite specificity
• Abnormal tissue proliferation and epinasty
• Improved drought resistance always
• Complete inhibition of photosynthesis

Correct Answer: Abnormal tissue proliferation and epinasty

Q38. Which hormonal change is typically associated with fruit ripening in climacteric fruits?

• Decrease in ethylene production
• Ethylene production surge and increased respiration
• Massive increase in ABA causing hardening
• Complete shutdown of cytokinin synthesis

Correct Answer: Ethylene production surge and increased respiration

Q39. Which enzyme is critical in converting ACC to ethylene in plants?

• ACC synthase
• ACC oxidase
• Rubisco
• Auxin oxidase

Correct Answer: ACC oxidase

Q40. Which PGR is commonly used to promote seed germination and stem elongation in experimental setups?

• Abscisic acid (ABA)
• Gibberellic acid (GA3)
• Cytokinin (BAP)
• Ethylene inhibitor

Correct Answer: Gibberellic acid (GA3)

Q41. Which measurement is critical when formulating PGR-containing agricultural products for consistent dosing?

• Viscosity only
• Active ingredient concentration and stability
• Packaging color
• Odor intensity

Correct Answer: Active ingredient concentration and stability

Q42. Which PGR is implicated in promoting chloroplast development and delaying leaf senescence?

• Ethylene
• Cytokinins
• ABA
• Jasmonic acid

Correct Answer: Cytokinins

Q43. Which factor influences the sensitivity of plant tissues to applied PGRs?

• Developmental stage, tissue type, and receptor expression levels
• Only ambient temperature
• Only soil pH
• Only planting density

Correct Answer: Developmental stage, tissue type, and receptor expression levels

Q44. Which PGR inhibitor is used experimentally to study gibberellin function by blocking its biosynthesis?

• Uniconazole or paclobutrazol
• Kinetin
• 2,4-D
• Salicylic acid

Correct Answer: Uniconazole or paclobutrazol

Q45. In the context of pharmaceutics, why is control of PGR residues in herbal drugs important?

• They affect taste only
• PGR residues can alter therapeutic potency and pose safety/regulatory concerns
• PGRs have no impact on human health
• They only change color of extracts

Correct Answer: PGR residues can alter therapeutic potency and pose safety/regulatory concerns

Q46. Which bioassay measures cytokinin activity by promoting greening and chlorophyll synthesis in cytokinin-responsive tissues?

• Amaranth root inhibition
• Tobacco callus inhibition
• Cucumber cotyledon expansion or chlorophyll retention assays
• Avena coleoptile elongation

Correct Answer: Cucumber cotyledon expansion or chlorophyll retention assays

Q47. Which plant hormone signaling often involves phosphorylation cascades mediated by histidine kinases?

• Auxin signaling
• Cytokinin signaling
• Ethylene biosynthesis only
• Brassinosteroid transport only

Correct Answer: Cytokinin signaling

Q48. Salicylic acid (SA) primarily contributes to which pharmaceutical-relevant plant response?

• Growth promotion only
• Systemic acquired resistance and induction of defense-related secondary metabolites
• Stomatal opening exclusively
• Promotion of seed dormancy

Correct Answer: Systemic acquired resistance and induction of defense-related secondary metabolites

Q49. Which laboratory precaution is important when extracting fragile PGRs for analysis?

• Expose extracts to strong light and heat
• Use cold, dark conditions and antioxidants to prevent degradation
• Never filter samples
• Use concentrated acids without neutralization

Correct Answer: Use cold, dark conditions and antioxidants to prevent degradation

Q50. In designing experiments to enhance alkaloid production using PGRs, which approach is most rational?

• Randomly apply high doses of all hormones
• Optimize type, concentration, timing, and combination of specific PGRs and monitor metabolite pathways
• Only alter light without studying PGRs
• Rely exclusively on genetic modification without PGR trials

Correct Answer: Optimize type, concentration, timing, and combination of specific PGRs and monitor metabolite pathways

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com