Plant Growth and DevelopmentNEET MCQs with solutions
Plant Growth and Development covers how plants grow, differentiate and respond to their environment, and the five plant growth regulators that control it all. NEET questions test the discovery of each hormone, its specific effects and uses, and the terms for growth curves, photoperiodism and vernalisation.
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- 11 Biology
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- 24 questions
- In the RankUp app
- 533 questions
- ELITE questions
- 53
- NCERT topics
- 6
Practise 24 questions
Tap an option to check it. Questions from every NCERT topic in this chapter, from easy to hard.
Q1Growth and Its Phases
In geometric growth, if both daughter cells produced by mitosis retain the capacity to divide, the growth rate is:
Not quite — the answer is A.
In geometric growth, each mitosis produces two dividing cells — producing an exponential increase (2→4→8→16). This is the initial phase in plants. Arithmetic growth (B) describes the pattern where only one daughter cell retains meristematic activity.
Q2Growth and Its Phases
Redifferentiation results in cells that:
Not quite — the answer is D.
After dedifferentiation allows cell division, the progeny cells undergo redifferentiation — maturing into specialized cells that permanently lose mitotic capacity. Option B confuses redifferentiation with continued meristematic activity.
Q3Growth and Its Phases
The plateau (stationary phase) observed in the sigmoid growth curve occurs primarily because:
Not quite — the answer is D.
The stationary phase results from limiting factors (nutrients, space, water) matching the organism's growth potential — not meristem loss (A) or auxin inhibition (B). Vacuolation (C) is an elongation-phase event, not the cause of plateau.
Q4Growth and Its Phases
During the sigmoid growth curve, the phase showing maximum absolute growth rate is:
Not quite — the answer is C.
The log phase represents the period of most rapid, exponential cell division. The stationary phase (B) is a common trap — it appears "maximum" because growth is sustained, but rate actually plateaus here due to limiting factors.
Q5Plant Growth Regulators (Introduction and Discovery)
The chemical nature of gibberellins is best described as:
Not quite — the answer is C.
Gibberellins are diterpenoid acids — a class of terpenoids. This distinguishes them from auxins (indole compounds), cytokinins (adenine derivatives), and ethylene (simple hydrocarbon). Option A is cytokinin's chemical nature — the most common swap error in NEET questions on this concept.
Q6Plant Growth Regulators (Introduction and Discovery)
In the context of PGR discovery, Paal's experiment (1919) demonstrated that:
Not quite — the answer is A.
Paal (1919) placed the isolated coleoptile tip asymmetrically on the decapitated stump and observed curvature in the dark — proving that the tip substance itself (not light) causes differential growth. This preceded Went's chemical isolation. Option C (Blaauw's hypothesis) is a tempting wrong answer.
Q7Plant Growth Regulators (Introduction and Discovery)
Which of the following correctly pairs a PGR with its chemical nature?
Not quite — the answer is D.
IAA (indole-3-acetic acid) is an indole compound. Gibberellins are diterpenoids (not adenine derivatives). Cytokinins are adenine derivatives (not diterpenoids). Ethylene is a simple two-carbon compound (CH₂=CH₂). Options A, B, and C each swap the chemical nature between PGRs — a classic NEET-style cross-matching trap.
Q8Auxins Gibberellins and Cytokinins
Cytokinins are primarily associated with which physiological process?
Not quite — the answer is B.
Cytokinins promote cytokinesis (cell division) and cell proliferation — their name derives from this function. Cell wall loosening and elongation are auxin/gibberellin effects. Stomatal closure is ABA's role. Option D is gibberellin's primary stem effect — a high-frequency confusion trap.
Q9Auxins Gibberellins and Cytokinins
The first naturally occurring cytokinin isolated from plants was:
Not quite — the answer is C.
Zeatin (6-(4-hydroxy-3-methylbut-2-enyl)aminopurine) was the first cytokinin isolated from a natural plant source — immature corn (maize) kernels. Kinetin was discovered earlier but from autoclaved herring sperm DNA, an artificial non-plant source. Option B is the most common wrong answer on this question.
Q10Auxins Gibberellins and Cytokinins
Cytokinins are primarily synthesized in which plant organ and transported via which pathway?
Not quite — the answer is B.
Cytokinins are mainly synthesized in root apices (meristematic regions) and transported upward (acropetally) to aerial parts via the xylem — the opposite direction to auxin's basipetal phloem transport. Option A reverses both site and pathway — the most frequent confusion on this concept.
Q11Auxins Gibberellins and Cytokinins
Gibberellins promote stem elongation primarily by stimulating:
Not quite — the answer is C.
Gibberellins promote both cell elongation and cell division in internodal regions, leading to dramatic stem lengthening (as seen in bolting). They do not affect chlorophyll degradation — Option D is an ABA/ethylene effect. Option B is false — gibberellins do not close stomata.
Q12Auxins Gibberellins and Cytokinins
In apical dominance, the relationship between auxin and cytokinin is best described as:
Not quite — the answer is C.
Auxin from the apical bud inhibits lateral bud outgrowth (apical dominance). Cytokinin, synthesized in roots and transported up, counteracts auxin and promotes lateral bud growth. This antagonistic interaction explains why decapitation + cytokinin application maximally releases lateral buds. Option D reverses the roles — a PYQ-style trap.
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Get RankUp on Google PlayQ13Auxins Gibberellins and Cytokinins
Indole-3-acetic acid (IAA) is best described as:
Not quite — the answer is A.
IAA is the most common and principal naturally occurring auxin in higher plants, synthesized from tryptophan in shoot apices and young leaves. It is an indole compound, not a gibberellin or cytokinin. Option D confuses IAA with ethylene.
Q14Ethylene and Abscisic Acid
Horizontal plagiotropic growth of the stem in dark-grown seedlings under ethylene is part of:
Not quite — the answer is A.
The triple response (horizontal growth, stem swelling, inhibited elongation) is the defining ethylene response in etiolated seedlings. Bolting (C) is GA-induced rapid internode elongation.
Q15Ethylene and Abscisic Acid
Which hormone antagonizes gibberellin during seed dormancy maintenance?
Not quite — the answer is C.
ABA maintains dormancy while gibberellin breaks it — they are functional antagonists in seed germination control. Cytokinin (D) promotes growth and cell division, not dormancy.
Q16Ethylene and Abscisic Acid
Which of the following correctly explains why ethylene accelerates leaf senescence?
Not quite — the answer is B.
Ethylene upregulates hydrolytic and oxidative enzymes that break down proteins and chlorophyll, driving senescence. Auxin transport inhibition (A) promotes abscission — a related but distinct process.
Q17Ethylene and Abscisic Acid
Which of the following is NOT a component of the triple response?
Not quite — the answer is D.
Ethylene inhibits elongation — it shortens internodes and causes radial swelling. Increased internode elongation is the effect of gibberellins, making it the classic distractor here.
Q18Photoperiodism
A plant that flowers irrespective of photoperiod is termed:
Not quite — the answer is A.
Day neutral plants (tomato, cucumber, cotton) flower based on developmental age, not photoperiod. Rosette plant (D) describes a growth form seen in some LDPs — it is not a photoperiod response category.
Q19Photoperiodism
The hypothetical transmissible flowering stimulus produced in leaves in response to appropriate photoperiod is called:
Not quite — the answer is B.
Florigen is the proposed flowering hormone synthesized in leaves and transported to the shoot apex to induce floral initiation. Vernalin (C) is a similar hypothetical substance linked to vernalization — placed here as an ELITE-level distractor.
Q20Photoperiodism
Which of the following best explains why photoperiodic perception occurs in leaves but flowering response occurs at the shoot apex?
Not quite — the answer is B.
Leaves contain phytochrome which on appropriate photoperiodic induction produces florigen, transported via phloem to the shoot apex where floral meristem differentiation is initiated. The apex (D) is the response site, not the perception site.
Q21Photoperiodism
Which of the following is correctly identified as a short day plant?
Not quite — the answer is C.
Chrysanthemum is a classic SDP. Wheat (A) and barley (D) are LDPs — this pairing is a standard NEET trap. Spinach (B) is also an LDP.
Q22Vernalisation and Seed Dormancy
Reversal of the vernalisation effect by exposure to high temperature is called:
Not quite — the answer is B.
Devernalisation occurs when plants subjected to high temperature after cold treatment lose their acquired flowering competence. Photoperiodism relates to day-length response. Dormancy and senescence are unrelated reversal processes.
Q23Vernalisation and Seed Dormancy
The primary ecological advantage of seed dormancy is:
Not quite — the answer is A.
Dormancy prevents germination during adverse seasons, ensuring seeds survive until conditions are favourable. It does not accelerate flowering or growth. Water absorption is a germination process, not a dormancy function.
Q24Vernalisation and Seed Dormancy
In positively photoblastic seeds, which factor is essential to break dormancy and trigger germination?
Not quite — the answer is A.
Positively photoblastic seeds (e.g., lettuce) require light — specifically red light acting via phytochrome — to break dormancy. High humidity, soil pH, and nitrogen are not the primary triggers for light-sensitive seed germination.
ELITE question · AIR under 50 level
This chapter has 53 ELITE questions for students aiming at the very top. They are only in the app.
Unlock ELITE questions in the appPlant growth regulators and key terms
Quick revision: most questions in this chapter test these facts.
| Topic | Key fact |
|---|---|
| Arithmetic vs geometric growth | Arithmetic: one daughter cell keeps dividing (e.g. root elongating at a constant rate); geometric: both keep dividing, giving a sigmoid curve (lag, log, stationary phases) |
| Dedifferentiation | Mature cells regain the ability to divide, e.g. interfascicular cambium and cork cambium |
| Auxin discovery | Charles and Francis Darwin (canary grass coleoptile); F.W. Went isolated auxin from Avena coleoptile tips |
| Auxins | Natural: IAA, IBA; synthetic: NAA, 2,4-D (weedicide for dicot weeds); cause apical dominance, parthenocarpy in tomato, rooting of cuttings |
| Gibberellin discovery | E. Kurosawa — bakanae (foolish seedling) disease of rice caused by Gibberella fujikuroi |
| Gibberellins | More than 100 known (GA₃ best known); bolting in cabbage and beet; increase sugarcane yield; speed up malting |
| Cytokinin discovery | Skoog and Miller — kinetin from autoclaved herring sperm DNA; zeatin from corn kernels and coconut milk |
| Cytokinins | Promote cell division, overcome apical dominance, delay leaf senescence |
| Ethylene | Gaseous; ripens fruits, triple response in seedlings, promotes flowering in pineapple; ethephon releases ethylene |
| Abscisic acid | Stress hormone; closes stomata; induces seed dormancy; antagonist of gibberellins |
| Photoperiodism | Short-day, long-day and day-neutral plants; photoperiod is sensed by leaves; hypothetical signal: florigen |
| Vernalisation | Low-temperature treatment promotes flowering, e.g. winter wheat, barley, rye and biennials like sugarbeet, cabbage, carrot |
What the app covers in this chapter
533 questions in total, each with a detailed explanation.
| Growth and Its Phases | 40 |
| Plant Growth Regulators (Introduction and Discovery) | 40 |
| Auxins Gibberellins and Cytokinins | 42 |
| Ethylene and Abscisic Acid | 40 |
| Photoperiodism | 40 |
| Vernalisation and Seed Dormancy | 40 |
| Mixed practice and chapter tests | 291 |
Questions students ask
Is Plant Growth and Development important for NEET?
Yes. Most questions come from the five plant growth regulators — who discovered them, their chemical nature and their specific uses in agriculture — plus growth curves and photoperiodism.
Which topics should I revise first?
Start with the five plant growth regulators, their discovery and uses (use the table on this page), then growth phases and curves, and finish with photoperiodism, vernalisation and seed dormancy.
How many questions from this chapter are on RankUp?
The RankUp app has 533 questions on Plant Growth and Development, including 53 ELITE questions written for students aiming at AIR under 50. Every question has a detailed explanation.
Can I download these questions as a PDF?
Yes. The free PDF on this page has all 24 questions with the answer key and explanations. No signup is needed.
