Plant Growth and Development: hormones, tested one by one

Free questions

30 solved MCQs, answer marked and reasoning written out

Every question below is free to read — no sign-up, no email. 3 of them are real questions from past NEET papers. The other 242 questions in this chapter are in the book and in practice access.

1. Q1 Multi-statement analysis

   Regarding r in the exponential growth equation: (i) it is the relative growth rate (ii) it is a measure of the ability of the plant to produce new plant material (iii) it is referred to as the efficiency index (iv) the final size W1 does not depend on the initial size W0. How many are correct?

   1. 1.One
   2. 2.Two
   3. 3.ThreeCorrect answer
   4. 4.Four

   Why option 3 is the answer

   The trap: (i)–(iii) correct; the final size DOES depend on the initial size W0, so (iv) is wrong.

   What this is testing: what the term r in the exponential growth equation means, and what it does not change.

   (i)-(iii) are correct. r is the relative growth rate, it measures the plant's ability to produce new material, and it is also called the efficiency index. (iv) is the trap. The final size W1 very much DOES depend on the initial size W0 — the equation W1 = W0 e^rt multiplies W0 by the growth term, so a bigger starting size gives a bigger final size for the same r.

   So three statements are correct.

   The exponential equation carries W0 in it, so the starting size shapes the finish. Relative growth rate describes the rate, not the outcome.

   NCERT Class 11 Biology, page 170

2. Q2 Multi-statement analysis

   Cytokinin discovery: (i) F. Skoog observed callus proliferation from internodal segments of tobacco stems (ii) callus proliferated only if, besides auxins, the medium was supplemented with vascular tissue extracts, yeast extract, coconut milk or DNA (iii) Miller et al. (1955) identified and crystallised kinetin (iv) kinetin occurs naturally in plants. How many are correct?

   1. 1.One
   2. 2.Two
   3. 3.ThreeCorrect answer
   4. 4.Four

   Why option 3 is the answer

   The trap: (i)–(iii) correct; kinetin does NOT occur naturally in plants, so (iv) is wrong.

   What this is testing: the steps of Skoog's cytokinin discovery, and one fact about kinetin itself.

   (i)-(iii) are correct. F. Skoog saw callus proliferate from tobacco internodal segments only when the auxin-containing medium also had vascular tissue extract, yeast extract, coconut milk or DNA added; Miller and co-workers then identified and crystallised kinetin in 1955. (iv) is the trap. Kinetin does NOT occur naturally in plants — it came from autoclaved herring sperm DNA in the lab; the natural cytokinin found in plants is zeatin.

   So three statements are correct. Kinetin and zeatin are often swapped in questions — kinetin is the lab-derived one.

   Skoog saw the effect, Miller named the molecule. Coconut milk is the detail most often asked about this discovery.

   NCERT Class 11 Biology, page 176

3. Q3 Multi-statement analysis

   Discovery of PGRs: (i) Charles Darwin and Francis Darwin observed that coleoptiles of canary grass bent towards a unilateral light source (ii) they concluded that the tip of the coleoptile was the site of the transmittable influence (iii) auxin was isolated by F.W. Went from tips of coleoptiles of oat seedlings (iv) the discovery of each of the five major PGRs was carefully planned. How many are correct?

   1. 1.One
   2. 2.Two
   3. 3.ThreeCorrect answer
   4. 4.Four

   Why option 3 is the answer

   The trap: (i)–(iii) correct; the discovery of each of the five major PGRs was ACCIDENTAL, so (iv) is wrong.

   What this is testing: how the five major PGRs came to be discovered.

   (i)-(iii) are correct. Charles and Francis Darwin saw canary grass coleoptiles bend towards one-sided light, concluded the tip carried a transmissible influence, and F.W. Went later isolated auxin from oat coleoptile tips. (iv) is the trap. None of the five major PGR discoveries were carefully planned — every one of them was ACCIDENTAL, arising from an unrelated observation such as a disease, a light response or a ripening fruit.

   So three statements are correct. 'Carefully planned' contradicts the whole accidental-discovery theme this chapter builds on.

   The Darwins found the tip mattered; Went isolated what the tip made. Observation first, chemistry decades later.

   NCERT Class 11 Biology, page 174

4. Q4 Multi-statement analysis

   Quantitative comparisons of growth: (i) the measurement and comparison of total growth per unit time is the absolute growth rate (ii) growth per unit time expressed on a common basis is the relative growth rate (iii) two leaves may show the same absolute growth but different relative growth rates (iv) absolute and relative growth rates are always identical. How many are correct?

   1. 1.One
   2. 2.Two
   3. 3.ThreeCorrect answer
   4. 4.Four

   Why option 3 is the answer

   The trap: (i)–(iii) correct; the two rates can differ, so (iv) is wrong.

   What this is testing: the difference between absolute and relative growth rate.

   (i)-(iii) are correct. Absolute growth rate is total growth measured per unit time; relative growth rate expresses that growth on a common basis; and two leaves can show identical absolute growth while differing in relative growth rate. (iv) is the trap. The two rates are NOT always identical — (iii) just demonstrated that they can diverge, so this statement contradicts the one right before it.

   So three statements are correct. When two consecutive statements clash, the later one is usually the planted error.

   Absolute growth rate is how much; relative growth rate is how much per unit of what was already there. A small leaf can beat a large one on the second measure while losing on the first.

   NCERT Class 11 Biology, page 171

5. Q5 Multi-statement analysis

   Plasticity: (i) is the ability of plants to follow different pathways in response to environment or phases of life (ii) heterophylly in cotton, coriander and larkspur is an example (iii) the leaves of the juvenile plant differ in shape from those of the mature plant (iv) heterophylly in buttercup is due to the phase of life, not the environment. How many are correct?

   1. 1.One
   2. 2.Two
   3. 3.ThreeCorrect answer
   4. 4.Four

   Why option 3 is the answer

   The trap: (i)–(iii) correct; the buttercup's aerial and submerged leaves differ due to the ENVIRONMENT, so (iv) is wrong.

   What this is testing: whether heterophylly is driven by the plant's life-stage or by its environment.

   (i)-(iii) are correct. Plasticity lets plants follow different developmental pathways depending on environment or life stage; cotton, coriander and larkspur show heterophylly as an example, with juvenile leaves differing in shape from mature ones. (iv) is the trap. In buttercup, the aerial and submerged leaves differ because of the ENVIRONMENT — air versus water — not because of the plant's phase of life, which is the opposite cause from what the statement claims.

   So three statements are correct.

   Heterophylly is plasticity you can see. The same plant makes different leaves at different ages or in different water.

   NCERT Class 11 Biology, page 173

6. Q6 Multi-statement analysis

   Regarding water and growth: (i) plant cells grow in size by cell enlargement, which requires water (ii) turgidity of cells helps in extension growth (iii) water provides the medium for enzymatic activities needed for growth (iv) water plays no role in the water status of the plant. How many are correct?

   1. 1.One
   2. 2.Two
   3. 3.ThreeCorrect answer
   4. 4.Four

   Why option 3 is the answer

   The trap: (i)–(iii) correct; growth is intimately linked to the WATER STATUS of the plant, so (iv) is wrong.

   What this is testing: how tightly growth depends on a plant's water status.

   (i)-(iii) are correct. Cells enlarge in size using water, turgidity of cells drives extension growth, and water is the medium in which the enzymes needed for growth work. (iv) is the trap. It directly contradicts the previous three statements: water clearly does play a central role in the plant's water status and, through it, in growth — the statement says the opposite of what (i)-(iii) just established.

   So three statements are correct.

   Water enlarges the cell, carries the enzymes and supplies the turgor. Take it away and none of the other conditions matter.

   NCERT Class 11 Biology, page 171

7. Q7 Multi-statement analysis

   Regarding other growth conditions: (i) oxygen helps in releasing metabolic energy essential for growth (ii) nutrients are required for the synthesis of protoplasm (iii) nutrients act as a source of energy (iv) light and gravity have no effect on growth. How many are correct?

   1. 1.One
   2. 2.Two
   3. 3.ThreeCorrect answer
   4. 4.Four

   Why option 3 is the answer

   The trap: (i)–(iii) correct; environmental signals such as light and gravity DO affect growth, so (iv) is wrong.

   What this is testing: whether environmental signals like light and gravity matter for growth.

   (i)-(iii) are correct. Oxygen releases the metabolic energy growth needs, nutrients build new protoplasm, and nutrients also serve as an energy source. (iv) is the trap. Light and gravity clearly DO affect growth — they shape tropic responses and photomorphogenesis — so claiming they have no effect contradicts basic plant physiology covered elsewhere in this chapter.

   So three statements are correct.

   Light and gravity steer growth through tropisms and photoperiodism. Saying they have no effect denies most of the chapter.

   NCERT Class 11 Biology, page 171

8. Q8 Multi-statement analysis

   Regarding open differentiation: (i) differentiation in plants is open (ii) cells arising from the same meristem have different structures at maturity (iii) the final structure is determined by the location of the cell (iv) cells positioned away from root apical meristems differentiate as epidermis. How many are correct?

   1. 1.One
   2. 2.Two
   3. 3.ThreeCorrect answer
   4. 4.Four

   Why option 3 is the answer

   The trap: (i)–(iii) correct; cells away from the root apical meristem become ROOT-CAP cells, while those pushed to the periphery become epidermis, so (iv) is wrong.

   What this is testing: which fate belongs to cells positioned away from the root apical meristem.

   (i)-(iii) are correct. Differentiation in plants is open, cells from the same meristem can have different mature structures, and the final structure depends on the cell's location. (iv) is the trap. Cells positioned away from the root apical meristem, on the outer side, become ROOT-CAP cells — it is cells pushed to the periphery, not those away from the meristem in this sense, that become epidermis.

   So three statements are correct. Position decides fate, but the two positional outcomes are easy to swap.

   Position decides fate in a plant. A cell's structure at maturity depends on where it sits, not on which meristem it came from.

   NCERT Class 11 Biology, page 172

9. Q9 Assertion and Reason

   AssertionZeatin is a synthetic cytokinin that does not occur in plants.

   ReasonZeatin is a natural cytokinin isolated from corn kernels and coconut milk.

   1. 1.Both A and R are true and R is the correct explanation of A
   2. 2.Both A and R are true but R is not the correct explanation of A
   3. 3.A is true but R is false
   4. 4.A is false but R is trueCorrect answer

   Why option 4 is the answer

   The trap: A is false; R is true.

   What this is testing: whether zeatin is the natural or the synthetic cytokinin.

   A is false — zeatin is not synthetic; it does occur naturally in plants. R is true: zeatin is the natural cytokinin isolated from corn kernels and coconut milk, unlike kinetin, which was made in the laboratory from herring sperm DNA and does not occur naturally.

   So the answer is (4). This pair deliberately reverses the natural-versus-synthetic label that questions elsewhere attach correctly to kinetin.

   Zeatin is natural, from corn and coconut milk; kinetin is synthetic, from herring sperm DNA. Two cytokinins, two very different origins.

   NCERT Class 11 Biology, page 176

10. Q10 Assertion and Reason

    AssertionGrowth is measured by a variety of parameters.

    ReasonOne single maize root apical meristem can give rise to more than 17,500 new cells per hour.

    1. 1.Both A and R are true and R is the correct explanation of A
    2. 2.Both A and R are true but R is not the correct explanation of ACorrect answer
    3. 3.A is true but R is false
    4. 4.A is false but R is true

    Why option 2 is the answer

    The trap: Both are true statements about growth; the maize figure is a parallel illustration and does not explain the use of varied parameters.

    What this is testing: whether a single striking data point explains why growth needs many measuring parameters.

    Both A and R are true. Growth is indeed measured by a variety of parameters, and a maize root apical meristem really can produce more than 17,500 new cells an hour — but that one number is an illustration of rapid cell-number growth in maize specifically, not the general reason different systems need different parameters.

    So the answer is (2). A striking fact about one plant is not automatically the explanation for a broad methodological point.

    One number illustrates a claim without accounting for it. An example is evidence, not a reason.

    NCERT Class 11 Biology, page 168

11. Q11 Assertion and Reason

    AssertionThe discovery of each of the five major groups of PGRs was accidental.

    ReasonThe Darwins observed that the coleoptiles of canary grass bend towards a unilateral source of light.

    1. 1.Both A and R are true and R is the correct explanation of A
    2. 2.Both A and R are true but R is not the correct explanation of ACorrect answer
    3. 3.A is true but R is false
    4. 4.A is false but R is true

    Why option 2 is the answer

    The trap: Both are true; the Darwins' observation is one parallel instance and does not explain the accidental nature of all five discoveries.

    What this is testing: whether one famous observation explains why all five PGR discoveries were accidental.

    Both A and R are true. Every one of the five major PGR discoveries was indeed accidental, and the Darwins' observation of canary grass coleoptiles bending towards light is a genuine example of one such accidental discovery — but it explains only the auxin story, not the accidental nature of the other four PGRs' discoveries as a whole.

    So the answer is (2). One example illustrates the pattern; it does not, by itself, explain the pattern for every PGR.

    One accidental discovery does not explain why all five were accidental. An instance of a pattern is not its cause.

    NCERT Class 11 Biology, page 174

12. Q12 Assertion and Reason

    AssertionThe plant growth regulators are small, simple molecules of diverse chemical composition.

    ReasonPlant growth regulators are variously described as plant growth substances, plant hormones or phytohormones.

    1. 1.Both A and R are true and R is the correct explanation of A
    2. 2.Both A and R are true but R is not the correct explanation of ACorrect answer
    3. 3.A is true but R is false
    4. 4.A is false but R is true

    Why option 2 is the answer

    The trap: Both are true of PGRs; the alternative names are a parallel fact and do not explain their chemical simplicity.

    What this is testing: whether the alternative names for PGRs explain why they are chemically simple.

    Both A and R are true. PGRs are indeed small, simple molecules of diverse chemical composition, and they are indeed also called plant growth substances, plant hormones or phytohormones — but having several names is a fact about terminology, not an explanation for why the molecules themselves are chemically simple.

    So the answer is (2). A naming fact and a structural fact about the same group can both be true without one causing the other.

    Having several names is a fact about vocabulary, not about chemistry. Terminology never explains structure.

    NCERT Class 11 Biology, page 174

13. Q13 Assertion and Reason

    AssertionGibberellic acid is used to speed up the malting process in the brewing industry.

    ReasonThere are more than 100 gibberellins reported from widely different organisms such as fungi and higher plants.

    1. 1.Both A and R are true and R is the correct explanation of A
    2. 2.Both A and R are true but R is not the correct explanation of ACorrect answer
    3. 3.A is true but R is false
    4. 4.A is false but R is true

    Why option 2 is the answer

    The trap: Both are true of gibberellins; the number of known gibberellins is a parallel fact and does not explain the malting application.

    What this is testing: whether the sheer number of known gibberellins explains their use in brewing.

    Both A and R are true. GA3 is indeed used to speed up malting in brewing, and more than 100 gibberellins have indeed been reported from fungi and higher plants — but the large number of known gibberellins is a separate fact about the group's diversity, not the reason GA3 specifically helps malting.

    So the answer is (2). A count of how many gibberellins exist does not explain what one of them, GA3, does in an industrial process.

    A use and a count are unrelated facts. That over a hundred gibberellins exist says nothing about what GA3 is used for.

    NCERT Class 11 Biology, page 176

14. Q14 Assertion and Reason

    AssertionLateral meristems are responsible for the elongation of the plant axis.

    ReasonRoot and shoot apical meristems are responsible for the primary growth and elongation of the plant axis.

    1. 1.Both A and R are true and R is the correct explanation of A
    2. 2.Both A and R are true but R is not the correct explanation of A
    3. 3.A is true but R is false
    4. 4.A is false but R is trueCorrect answer

    Why option 4 is the answer

    The trap: A is false — lateral meristems increase girth; R is true.

    What this is testing: which meristems actually elongate the plant axis.

    A is false — lateral meristems are responsible for increasing GIRTH, not for elongation; elongation is the job of the apical meristems. R is true: root and shoot apical meristems are indeed responsible for primary growth and elongation of the axis.

    So the answer is (4). A takes the correct fact in R and wrongly reassigns it to the wrong kind of meristem.

    Apical for length, lateral for girth. Primary growth goes up, secondary growth goes out.

    NCERT Class 11 Biology, page 168

15. Q15 Assertion and Reason

    AssertionGrowth in plants is always determinate.

    ReasonPlants retain the capacity for unlimited growth throughout their life due to the presence of meristems.

    1. 1.Both A and R are true and R is the correct explanation of A
    2. 2.Both A and R are true but R is not the correct explanation of A
    3. 3.A is true but R is false
    4. 4.A is false but R is trueCorrect answer

    Why option 4 is the answer

    The trap: A is false — plant growth is generally INDETERMINATE; R is true.

    What this is testing: whether plant growth generally has a fixed endpoint.

    A is false — plant growth is generally INDETERMINATE, not determinate; plants can keep growing throughout their life rather than stopping at a fixed size. R is true: this indeterminate growth exists because meristems retain the capacity for unlimited growth throughout the plant's life.

    So the answer is (4). A contradicts the very fact R correctly states about meristems.

    Indeterminate is the word for plants, determinate for animals. Meristems are the reason for the difference.

    NCERT Class 11 Biology, page 167

16. Q16 Assertion and Reason

    AssertionGibberellic acid is denoted GA1 and was the last gibberellin to be discovered.

    ReasonGibberellic acid is denoted GA3 and was one of the first gibberellins to be discovered.

    1. 1.Both A and R are true and R is the correct explanation of A
    2. 2.Both A and R are true but R is not the correct explanation of A
    3. 3.A is true but R is false
    4. 4.A is false but R is trueCorrect answer

    Why option 4 is the answer

    The trap: A is false; R is true.

    What this is testing: which gibberellin was actually discovered first, GA1 or GA3.

    A is false — gibberellic acid is denoted GA3, not GA1, and it was among the FIRST gibberellins discovered, not the last. R is true: GA3 was indeed one of the first gibberellins identified and is still the most extensively studied.

    So the answer is (4). A reverses both the numbering and the discovery order that R states correctly.

    GA3 was among the first found and remains the most studied. The subscript is a discovery number, not a ranking.

    NCERT Class 11 Biology, page 176

17. Q17 Assertion and Reason

    AssertionLateral meristems cause an increase in the girth of the organs in which they are active.

    ReasonThe vascular cambium and cork cambium appear later in life in dicotyledonous plants and gymnosperms.

    1. 1.Both A and R are true and R is the correct explanation of A
    2. 2.Both A and R are true but R is not the correct explanation of ACorrect answer
    3. 3.A is true but R is false
    4. 4.A is false but R is true

    Why option 2 is the answer

    The trap: Both are true of lateral meristems; the time of their appearance is a parallel fact and does not explain the increase in girth.

    What this is testing: whether the timing of lateral meristem appearance explains the increase in girth.

    Both A and R are true. Lateral meristems do increase the girth of the organs where they are active, and the vascular and cork cambium do indeed appear later in life in dicots and gymnosperms — but when a meristem appears is a separate fact from how its activity increases girth.

    So the answer is (2). Timing of appearance and the growth effect produced are two different facts about the same meristems.

    When a meristem appears and what it does are separate facts. Timing never explains function.

    NCERT Class 11 Biology, page 168

18. Q18 Statement I and Statement II

    Statement IAuxin was isolated by F.W. Went from tips of coleoptiles of oat seedlings.

    Statement IIThe Darwins observed that coleoptiles of canary grass bend towards unilateral light.

    1. 1.Both Statement I and Statement II are correctCorrect answer
    2. 2.Both Statement I and Statement II are incorrect
    3. 3.Statement I is correct but Statement II is incorrect
    4. 4.Statement I is incorrect but Statement II is correct

    Why option 1 is the answer

    The trap: Both statements are correct.

    What this is testing: separating the observation of phototropism from the actual isolation of auxin.

    Both statements are correct. F.W. Went did isolate auxin from the tips of oat coleoptiles, and the Darwins, working earlier, did observe canary grass coleoptiles bending towards unilateral light — two genuine, sequential steps in the same discovery story.

    So the answer is (1). One statement covers the initial observation, the other the eventual isolation, and both are accurate as given.

    Observation came decades before isolation. The Darwins saw the effect in 1880; Went had the molecule by 1928.

    NCERT Class 11 Biology, page 174

19. Q19 Statement I and Statement II

    Statement ICytokinins help overcome apical dominance.

    Statement IICytokinins are synthesised in regions of rapid cell division such as root apices.

    1. 1.Both Statement I and Statement II are correctCorrect answer
    2. 2.Both Statement I and Statement II are incorrect
    3. 3.Statement I is correct but Statement II is incorrect
    4. 4.Statement I is incorrect but Statement II is correct

    Why option 1 is the answer

    The trap: Both statements are correct.

    What this is testing: where cytokinins come from and one of their effects.

    Both statements are correct. Cytokinins do help overcome apical dominance, working against auxin's inhibitory signal, and they are indeed synthesised in regions of rapid cell division such as root apices.

    So the answer is (1). Both statements are accurate, independent facts about cytokinin biology, with nothing here to contradict.

    Auxin from the shoot tip imposes apical dominance; cytokinin from the root releases it. The two hormones pull against each other.

    NCERT Class 11 Biology, page 177

20. Q20 Statement I and Statement II

    Statement IEthylene inhibits fruit ripening.

    Statement IIThe rise in respiration rate during fruit ripening is called the respiratory climactic.

    1. 1.Both Statement I and Statement II are correct
    2. 2.Both Statement I and Statement II are incorrect
    3. 3.Statement I is correct but Statement II is incorrect
    4. 4.Statement I is incorrect but Statement II is correctCorrect answer

    Why option 4 is the answer

    The trap: I incorrect (ethylene is highly effective in PROMOTING ripening); II correct.

    What this is testing: whether ethylene promotes or inhibits fruit ripening.

    Statement I is incorrect — ethylene is highly effective at PROMOTING fruit ripening, not inhibiting it; it is the very hormone applied commercially to trigger ripening. Statement II is correct: the rise in respiration rate that accompanies ripening is indeed called the respiratory climacteric.

    So the answer is (4). Statement I reverses ethylene's best-known effect in this whole chapter.

    Ethylene is the ripening hormone, applied deliberately to trigger it. Saying it inhibits ripening inverts its main commercial use.

    NCERT Class 11 Biology, page 177

21. Q21 Match the columns

    Match the cytokinin effect with the outcome:

    Column I	Column II
    (a) New leaves	(ii) promoted
    (b) Chloroplasts in leaves	(iii) promoted
    (c) Lateral shoot growth	(iv) delayed
    (d) Leaf senescence	(i) promoted

    1. 1.(a)-(iv), (b)-(ii), (c)-(i), (d)-(iii)
    2. 2.(a)-(iii), (b)-(i), (c)-(ii), (d)-(iv)Correct answer
    3. 3.(a)-(iii), (b)-(ii), (c)-(i), (d)-(iv)
    4. 4.(a)-(iv), (b)-(i), (c)-(ii), (d)-(iii)

    Why option 2 is the answer

    The trap: Cytokinins promote leaves, chloroplasts and lateral shoots, and delay senescence.

    What this is testing: matching cytokinin's four textbook effects to their correct outcomes.

    Option (2) is correct: cytokinins promote the formation of new leaves, promote chloroplasts in leaves, promote lateral shoot growth, and delay leaf senescence — three 'promotes' and one 'delays', all in the plant's favour.

    Option (1) and option (4) shuffle 'delayed' onto the wrong row and scramble the promoted effects; option (3) swaps chloroplasts and lateral shoot growth. Since every effect here genuinely points the same direction — supporting fresh, active tissue — the only real trap is which specific outcome word (promoted vs delayed) attaches to which row.

    NCERT Class 11 Biology, page 177

22. Q22 Match the columns

    Match the growth rate term with its definition:

    Column I	Column II
    (a) Absolute growth rate	(i) growth per unit time per unit initial parameter
    (b) Relative growth rate	(ii) the relative growth rate r
    (c) Efficiency index	(iv) increased growth per unit time
    (d) Growth rate	(iii) total growth per unit time

    1. 1.(a)-(i), (b)-(iii), (c)-(ii), (d)-(iv)
    2. 2.(a)-(iii), (b)-(ii), (c)-(i), (d)-(iv)
    3. 3.(a)-(iv), (b)-(i), (c)-(ii), (d)-(iii)
    4. 4.(a)-(iii), (b)-(i), (c)-(ii), (d)-(iv)Correct answer

    Why option 4 is the answer

    The trap: Absolute-total per unit time; relative-per unit initial parameter; r-efficiency index.

    What this is testing: matching the growth-rate terms to their precise definitions.

    Option (4) is correct: absolute growth rate is total growth per unit time, relative growth rate is growth per unit time per unit of the initial parameter, the efficiency index is another name for the relative growth rate r, and growth rate itself is the increased growth per unit time.

    Option (1) swaps absolute and relative growth rate; option (2) swaps relative growth rate and the efficiency index; option (3) scrambles the set further. Since the efficiency index and relative growth rate are literally the same quantity under two names, that pairing is the one most often broken apart by a wrong option.

    NCERT Class 11 Biology, page 171

23. Q23 Match the columns

    Match the ethylene effect with the seedling/organ:

    Column I	Column II
    (a) Apical hook formation	(iii) deep water rice
    (b) Horizontal growth	(i) potato tubers
    (c) Internode elongation	(iv) seedlings
    (d) Sprouting	(ii) dicot seedlings

    1. 1.(a)-(iv), (b)-(ii), (c)-(iii), (d)-(i)
    2. 2.(a)-(ii), (b)-(iii), (c)-(iv), (d)-(i)
    3. 3.(a)-(ii), (b)-(iv), (c)-(iii), (d)-(i)Correct answer
    4. 4.(a)-(i), (b)-(iv), (c)-(iii), (d)-(ii)

    Why option 3 is the answer

    The trap: Apical hook-dicot seedlings, horizontal growth-seedlings, elongation-deep water rice, sprouting-potato.

    What this is testing: matching four ethylene effects to the seedling type or organ they occur in.

    Option (3) is correct: ethylene causes apical hook formation in dicot seedlings, horizontal growth in seedlings generally, internode elongation in deep water rice, and sprouting in potato tubers.

    Option (1) swaps apical hook formation and horizontal growth; option (2) swaps horizontal growth and internode elongation; option (4) scrambles the set. Ethylene produces a wide, varied set of responses across different plant parts, so the trap is attaching the right response to the right organ rather than mixing up which seedling shows which behaviour.

    NCERT Class 11 Biology, page 177

24. Q24 Match the columns

    Match the PGR effect with the correct hormone:

    Column I	Column II
    (a) Induces rooting in a twig	(i) abscisic acid
    (b) Quickly ripens a fruit	(ii) cytokinin
    (c) Delays leaf senescence	(iii) ethylene
    (d) Induces stomatal closure	(iv) auxin

    1. 1.(a)-(iii), (b)-(iv), (c)-(ii), (d)-(i)
    2. 2.(a)-(iv), (b)-(ii), (c)-(iii), (d)-(i)
    3. 3.(a)-(i), (b)-(iii), (c)-(ii), (d)-(iv)
    4. 4.(a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)Correct answer

    Why option 4 is the answer

    The trap: Rooting-auxin, ripening-ethylene, delaying senescence-cytokinin, stomatal closure-ABA.

    What this is testing: matching four everyday plant effects to the single hormone responsible for each.

    Option (4) is correct: auxin induces rooting in a twig, ethylene quickly ripens a fruit, cytokinin delays leaf senescence, and abscisic acid induces stomatal closure — four distinct, non-overlapping hormone-to-effect pairings.

    Option (1) swaps auxin and ethylene; option (2) swaps ethylene and cytokinin; option (3) moves stomatal closure onto auxin instead of ABA. Each of these four effects is the single most textbook-classic association for its hormone, so keeping rooting-ripening-delay-closure tied to auxin-ethylene-cytokinin-ABA in that order avoids all three wrong options.

    NCERT Class 11 Biology, page 178

25. Q25 Exception / incorrect

    All are phases of the sigmoid curve EXCEPT:

    1. 1.lag phase
    2. 2.log phase
    3. 3.stationary phase
    4. 4.linear phaseCorrect answer

    Why option 4 is the answer

    The trap: The sigmoid curve has lag, log and stationary phases.

    What this is testing: which named phase does not belong to the sigmoid growth curve.

    Lag phase, log phase and stationary phase are the three genuine phases of the sigmoid curve. Linear phase is the exception — it is not one of the sigmoid curve's named stages at all; a 'linear' pattern instead describes arithmetic growth's whole curve, not a single phase within geometric growth.

    The trap borrows a term from arithmetic growth and inserts it among the sigmoid curve's real phases.

    NCERT Class 11 Biology, page 170

26. Q26 Exception / incorrect

    All are true of lateral meristems EXCEPT:

    1. 1.they include vascular cambium
    2. 2.they include cork cambium
    3. 3.they cause elongation of the axisCorrect answer
    4. 4.they cause increase in girth

    Why option 3 is the answer

    The trap: Apical meristems cause elongation.

    What this is testing: whether lateral meristems elongate the axis or widen it.

    Including vascular cambium and cork cambium, and causing an increase in girth, are all genuine, correct facts about lateral meristems. Causing elongation of the axis is the exception — elongation is the job of the APICAL meristems; lateral meristems instead increase girth, the opposite growth dimension.

    The trap borrows the apical meristems' role and mistakenly attaches it to the lateral meristems in the same sentence.

    NCERT Class 11 Biology, page 168

27. Q27 Sequence / ordering

    Correct chronological order of PGR discoveries:

    1. 1.Cousins (1910) → Kurosawa (1926) → Miller et al. (1955)Correct answer
    2. 2.Kurosawa (1926) → Cousins (1910) → Miller (1955)
    3. 3.Miller (1955) → Kurosawa (1926) → Cousins (1910)
    4. 4.Kurosawa → Miller → Cousins

    Why option 1 is the answer

    The trap: 1910 → 1926 → 1955.

    What this is testing: the chronological order of three separate PGR discovery events.

    The correct order is Cousins in 1910, then Kurosawa in 1926, then Miller and co-workers in 1955 — ethylene's ripening clue came first, followed by the gibberellin-bakanae link, and finally the crystallisation of kinetin.

    Every wrong option places these dates out of sequence. Since each discovery belongs to a different PGR studied independently, the only way to order them correctly is by the actual year attached to each researcher's name.

    NCERT Class 11 Biology, page 176

28. Q28 NEET 2024

    Match the plant growth regulator with its effect:

    Column I	Column II
    (a) Abscisic acid	(i) Promotes bolting in beet, cabbage
    (b) Ethylene	(ii) Helps in nutrient mobilisation
    (c) Gibberellin	(iii) Helps seeds withstand desiccation
    (d) Cytokinin	(iv) Promotes female flowers in cucumber

    1. 1.(a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)
    2. 2.(a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)Correct answer
    3. 3.(a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)
    4. 4.(a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)

    Why option 2 is the answer

    The trap: ABA-desiccation tolerance, Ethylene-female flowers, Gibberellin-bolting, Cytokinin-nutrient mobilisation.

    What this is testing: matching four plant growth regulators to their correct effects.

    Option 2 is correct: abscisic acid helps seeds withstand desiccation, ethylene promotes female flowers in cucumber, gibberellin promotes bolting in beet and cabbage, and cytokinin helps in nutrient mobilisation — four regulators, four accurately paired roles.

    Option 1 swaps ABA and ethylene's pairings with gibberellin and cytokinin's. Option 3 reverses the whole set. Option 4 shifts every pairing by one position along the list.

    ABA's desiccation-tolerance role and ethylene's female-flower-promoting role are easy to swap under pressure since both sound like "stress-related" effects — keep them tied to their specific, distinct outcomes.

    NCERT Class 11 Biology, pages 176-178

29. Q29 NEET 2023

    Match the plant growth regulator with its effect:

    Column I	Column II
    (a) Auxin	(iii) Overcoming apical dominance
    (b) Gibberellin	(ii) Promotes female flower formation in cucumber
    (c) Cytokinin	(iv) Promotes flowering in pineapple
    (d) Ethylene	(i) Increase in length of grape stalks

    1. 1.(a)-(ii), (b)-(iii), (c)-(i), (d)-(iv)
    2. 2.(a)-(iv), (b)-(i), (c)-(iii), (d)-(ii)Correct answer
    3. 3.(a)-(i), (b)-(iv), (c)-(ii), (d)-(iii)
    4. 4.(a)-(iii), (b)-(ii), (c)-(iv), (d)-(i)

    Why option 2 is the answer

    The trap: Auxin-pineapple flowering, Gibberellin-grape stalk elongation, Cytokinin-overcomes apical dominance, Ethylene-female flowers in cucumber.

    What this is testing: matching four plant growth regulators to the effects NCERT attributes to each.

    Auxin promotes flowering in pineapple. Gibberellin increases the length of grape stalks. Cytokinin overcomes apical dominance — auxin causes it, cytokinin releases it. Ethylene increases the number of female flowers in cucumber.

    Two of these are the ones students reverse. Apical dominance belongs to auxin as a CAUSE and to cytokinin as a CURE, so the word appears under both hormones in the chapter and the direction is what matters. And the grape stalk is gibberellin's, not cytokinin's — gibberellin elongates, cytokinin divides.

    The trap: cucumber and pineapple are both flowering effects, and both sit close together in the chapter. Pineapple flowering is auxin's here; the female-flower effect in cucumber is ethylene's.

    NCERT Class 11 Biology, pages 174-177

30. Q30 NEET 2020

    Which is NOT an inhibitory substance governing seed dormancy?

    1. 1.Para-ascorbic acid
    2. 2.Abscisic acid
    3. 3.Gibberellic acidCorrect answer
    4. 4.Phenolic acid

    Why option 3 is the answer

    The trap: Gibberellic acid BREAKS seed dormancy; it is not an inhibitor of germination.

    What this is testing: identifying which listed substance is NOT an inhibitor of seed germination.

    Gibberellic acid — option 3 — is the one substance among the four that is NOT an inhibitor; it actually BREAKS seed dormancy and promotes germination, the opposite role to the other three.

    Options 1, 2 and 4, para-ascorbic acid, abscisic acid and phenolic acid, are all genuine inhibitory substances that help keep seeds dormant until conditions are favourable.

    Gibberellic acid's growth-promoting, dormancy-breaking role makes it the odd one out on a list otherwise made up of inhibitors — that contrast is exactly what this question checks.

    NCERT Class 11 Biology, pages 174-178