🔬 Biology · Class 11 · NEET
Plant Growth and Development - Practice Questions with Answers 75 free MCQs on Plant Growth and Development, each with its own worked answer and explanation. Phases of plant growth, the five classical plant hormones plus newer ones, photoperiodism, vernalization, and seed dormancy.
Take the timed Plant Growth and Development chapterwise test → 75 practice questions on Plant Growth and Development , sorted Easy → Hard. Try each one first, then open its answer page for the worked explanation. Want the full theory first? Read the Plant Growth and Development notes .
Geometric Growth: the Sigmoid Curve time growth lag phase log/exponential phase stationary phase Growth starts slow, accelerates rapidly, then plateaus as resources become limiting Geometric growth (where both daughter cells keep dividing) produces this classic S-shaped curve: a slow lag phase, a rapid exponential phase, and a levelling-off stationary phase as nutrients or space become limiting - the same fundamental pattern seen in population growth.
Easy - 25 questions Q1.
The natural auxin found in plants is:
A Indole-3-acetic acidB Gibberellic acidC Abscisic acidD Zeatin ribosideShow answer & explanation →
Q3.
Seedless (parthenocarpic) fruits can be induced by spraying the hormone:
A EthyleneB CytokininC AuxinD Abscisic acidShow answer & explanation →
Q5.
Growth in which one daughter cell keeps dividing while the other matures, giving a linear increase, is:
A Arithmetic growthB Geometric growthC Exponential growthD Logarithmic growthShow answer & explanation →
Q6.
Gibberellins promote:
A Adventitious root initiation exclusively, with no effect on shoot tissueB Stomatal closure via guard cell turgor loss under water stressC Stem elongation and seed germinationD Climacteric fruit ripening through ethylene biosynthesis inductionShow answer & explanation →
Q7.
Auxin promotes:
A Cell elongation and phototropismB Cell division at root tipC Leaf senescenceD Stomatal closureShow answer & explanation →
Q8.
Ethylene is a plant hormone involved in:
A Stem elongation driven by cell wall loosening at the apical meristemB Fruit ripening and abscissionC Adventitious root formation at the cut ends of stem cuttingsD Directional bending of shoots toward a unidirectional light sourceShow answer & explanation →
Q9.
ABA (Abscisic acid) causes:
A Rapid stem elongation and internode growthB Triggering of seed germination processesC Stomatal closure and dormancyD Acceleration of fruit ripening and softeningShow answer & explanation →
Q10.
Apical dominance in plants is regulated by:
A Gibberellins diffusing downward from the shoot apex to suppress lateral budsB Cytokinins transported upward from the root tip through the xylem streamC Auxin (IAA) from apical budD Ethylene accumulating locally at axillary bud junctionsShow answer & explanation →
Q11.
Cytokinins, a class of plant hormones, mainly promote:
A Stomatal closureB Stem elongationC Cell divisionD Fruit ripeningShow answer & explanation →
Q12.
Which plant hormone is commonly associated with promoting fruit ripening?
A EthyleneB GibberellinC AuxinD CytokininShow answer & explanation →
Q13.
The bending of a plant shoot toward light is an example of:
A GeotropismB ThigmotropismC HydrotropismD PhototropismShow answer & explanation →
Q14.
Seed dormancy in many plants helps ensure that:
A Seeds germinate immediately after dispersal regardless of conditionsB Germination occurs only under favourable environmental conditionsC Germination always requires artificial chemical treatmentD Seeds lose viability shortly after they are formedShow answer & explanation →
Q15.
Differentiation in plant development refers to the process by which:
A Mature cells revert back to a dividing meristematic stateB Cells derived from meristems mature to perform specific functionsC Plant organs increase only in number, not in specializationD Cells divide repeatedly without any change in structureShow answer & explanation →
Q16.
The permanent, irreversible increase in the size of a plant is called:
A growthB respirationC transpirationD digestionShow answer & explanation →
Q18.
The chemical substances that regulate plant growth are called:
A plant hormonesB only enzymesC simple vitaminsD soil mineralsShow answer & explanation →
Q19.
The hormone that promotes cell elongation and shoot growth is:
A auxinB abscisic acidC ethyleneD florigenShow answer & explanation →
Q22.
Growth in a plant occurs mainly at the:
A tips of roots and shootsB the middle of the old stemC the fully grown old leavesD the outer woody barkShow answer & explanation →
Q23.
The bending of a plant shoot toward a source of light is called:
A phototropismB geotropismC hydrotropismD thigmotropismShow answer & explanation →
Q24.
The downward growth of roots in response to gravity is called:
A geotropismB phototropismC hydrotropismD chemotropismShow answer & explanation →
Q25.
The process by which a seed grows into a seedling is called:
A germinationB pollinationC transpirationD respirationShow answer & explanation →
Medium - 25 questions Q26.
The weed-killer 2,4-D, which destroys broad-leaved dicot weeds, is a synthetic:
A CytokininB AuxinC GibberellinD EthyleneShow answer & explanation →
Q27.
In the brewing industry, malting (breakdown of barley starch) is speeded up by:
A AuxinsB CytokininsC GibberellinsD AbscisinsShow answer & explanation →
Q28.
Ethylene for artificial fruit ripening is commonly released from the compound:
A IAAB NAAC 2,4-DD EthephonShow answer & explanation →
Q29.
Long-day plants flower when the night length is:
A Shorter than a critical lengthB Longer than a critical lengthC Exactly twelve hours longD Of no importance at allShow answer & explanation →
Q30.
The plant organ that actually perceives the photoperiodic (day-length) stimulus is the:
A The root tipB The leafC The flower budD The stem apexShow answer & explanation →
Q31.
Vernalization is:
A A plant's photoperiodic response to the relative length of day versus nightB Requirement for cold treatment to induce floweringC Application of elevated temperature treatment to accelerate vegetative growthD Prolonged exposure to drought stress that triggers stomatal closureShow answer & explanation →
Q32.
Cytokinin promotes:
A Stem elongation by loosening cell walls at the subapical meristemB Cell division and delays senescenceC Climacteric fruit ripening coupled with ethylene releaseD Primary root elongation exclusively, with no effect on lateral shootsShow answer & explanation →
Q33.
Senescence in leaves is triggered by:
A A sharp rise in cytokinin levels delivered from the root systemB Decreased auxin and increased ethylene and ABAC An isolated drop in ambient temperature unaccompanied by hormonal changeD An increase in available soil water supply to the root systemShow answer & explanation →
Q34.
Phytochrome is a photoreceptor that responds to:
A Blue light exclusively, detected through a flavin chromophoreB Red and far-red light (Pr and Pfr forms)C Ultraviolet light absorbed by UVR8 photoreceptor proteinsD Green light wavelengths absorbed by chlorophyll-associated pigmentsShow answer & explanation →
Q35.
Photoperiodism refers to:
A The overall rate of carbon fixation occurring during daylight hoursB Response of plants to the relative lengths of day and night for floweringC Light-induced changes in chlorophyll concentration affecting leaf colorD Rapid guard cell turgor changes that open stomata at sunriseShow answer & explanation →
Q36.
Auxin transport is primarily:
A Acropetal, moving upward from the root tip toward the shoot apexB Polar (from shoot apex downward, basipetal)C Non-directional, diffusing randomly through ground tissue without polarityD Confined entirely to root tissue, absent from the shoot systemShow answer & explanation →
Q37.
Gravitropism in roots is caused by:
A Auxin accumulating on the upper side, accelerating elongation there insteadB Auxin accumulating on the lower side, inhibiting root elongation thereC Uniform auxin distribution across the root cap with no lateral asymmetryD Cytokinin redistribution within statocytes sensing the gravity vectorShow answer & explanation →
Q38.
Apical dominance, in which a growing apical bud suppresses the growth of lateral buds, is mainly caused by:
A Ethylene released from leaves undergoing senescenceB Gibberellin transported upward from the root systemC High auxin levels produced by the apical bud itselfD Cytokinin moving downward from the shoot tipShow answer & explanation →
Q39.
Abscisic acid is often referred to as a stress hormone in plants because it:
A Induces stomatal closure and seed dormancy under stress like droughtB Stimulates internode elongation within the stem under usual circumstancesC Promotes faster cell division in favourable conditions as generally observedD Speeds up fruit ripening together with ethylene in typical laboratory settingsShow answer & explanation →
Q40.
Ethylene's effect in promoting fruit ripening is widely exploited commercially because it:
A Promotes ongoing vegetative growth of the fruit as widely reportedB Stops sugar formation within the ripening fruit according to most studiesC Triggers starch-to-sugar conversion and softening of fruit tissueD Halts respiration within the ripening fruit cells in the majority of documented casesShow answer & explanation →
Q41.
The hormone that promotes stomatal closure and maintains seed dormancy is:
A abscisic acidB plain auxinC plain cytokininD plain gibberellinShow answer & explanation →
Q42.
The hormone that breaks seed dormancy and promotes stem elongation is:
A gibberellinB abscisic acidC ethyleneD florigenShow answer & explanation →
Q43.
The stage of growth in which cells rapidly enlarge is the ___ phase:
A elongationB meristematicC maturationD dormancyShow answer & explanation →
Q44.
Apical dominance, in which the main shoot suppresses side shoots, is caused by:
A auxinB ethyleneC abscisic acidD florigenShow answer & explanation →
Q45.
The directional growth of a tendril in response to touch is called:
A thigmotropismB phototropismC geotropismD hydrotropismShow answer & explanation →
Q46.
A graph of growth against time typically gives a ___ curve:
A sigmoid (S-shaped)B a straight-lineC a circular oneD a zigzag oneShow answer & explanation →
Q47.
Differentiation is the process by which cells become ___ for particular functions:
A specialisedB identicalC smallerD non-livingShow answer & explanation →
Q49.
The directional growth of a plant part in response to a stimulus is called a:
A tropismB nastic movementC nerve reflexD circulationShow answer & explanation →
Q50.
Vernalisation is the promotion of flowering by exposure to:
A low temperatureB high lightC severe droughtD strong heatShow answer & explanation →
Hard - 25 questions Q51.
The coleoptile bending experiments that first hinted at auxin were carried out by:
A Gregor MendelB Robert HookeC The two DarwinsD Melvin CalvinShow answer & explanation →
Q52.
The Avena coleoptile curvature test is a bioassay used to measure:
A Cytokinin activityB Gibberellin levelC Ethylene amountD Auxin activityShow answer & explanation →
Q53.
Light-requiring seeds such as lettuce are stimulated to germinate by the ___ form of phytochrome:
A The Pfr formB The Pr formC No phytochromeD An auxin formShow answer & explanation →
Q54.
Applying cytokinin to a bud that is suppressed by apical dominance will:
A Keep it fully dormantB Make it grow outC Kill the whole budD Cause early leaf fallShow answer & explanation →
Q55.
The ability of a differentiated plant cell to regenerate a whole plant is called:
A SenescenceB DormancyC TotipotencyD AbscissionShow answer & explanation →
Q56.
Florigen is now identified as:
A A specialized auxin derivative synthesized directly within the shoot apical meristem regionB FT protein (Flowering Locus T) produced in leaves, transported to shoot apex via phloemC Gibberellin A3 synthesized locally within developing floral primordia tissueD A cytokinin variant transported acropetally upward from the root system belowShow answer & explanation →
Q57.
Jasmonates (jasmonic acid) are plant hormones that:
A Promote climacteric fruit ripening mainly through ethylene synergism during late development according to standard textbooksB Activate defense responses against herbivory and pathogens, regulate pollen development, and inhibit growthC Promote stomatal opening by activating proton pumps within guard cell membranes directly in general practiceD Bind the same TIR1 receptor as auxin and trigger largely identical downstream signaling pathways as frequently describedShow answer & explanation →
Q58.
Epigenetic regulation of flowering time in Arabidopsis involves:
A Direct DNA methylation of the FT gene promoter region alone, with little histone involvement noted in typical laboratory settingsB FLC (Flowering Locus C) - a repressor of flowering - silenced by vernalization through polycomb-mediated H3K27me3 markingC Gibberellin signaling acting mainly alone through the DELLA degradation pathway each time under usual circumstancesD Mainly transcriptional control with little chromatin-level modification involved overall according to most researchersShow answer & explanation →
Q59.
Calmodulin in plant signal transduction:
A Functions as a receptor tyrosine kinase embedded directly in the plasma membrane structure under most conditions encounteredB Is a calcium sensor that, when Ca<sup>2+</sup> bound, activates multiple target enzymes (kinases, phosphatases, NOSs)C Operates mainly within guard cells, largely absent from other plant tissues studied as frequently observed in practiceD Is itself a diffusible plant hormone synthesized within the shoot apex region in many documented casesShow answer & explanation →
Q60.
Phytochrome-interacting factors (PIFs) are:
A Red light receptors themselves, which absorb photons directly through a bound chromophore group structure according to conventional understandingB Transcription factors that interact with Pfr form of phytochrome and are degraded upon light activation, derepressing light-responsive genesC Plastid-localized enzymes responsible for synthesizing the phytochrome chromophore precursor molecule in routine practice overall in most casesD DNA repair proteins that are activated specifically in response to ultraviolet light exposure events under typical conditions according to standard textbooksShow answer & explanation →
Q61.
Strigolactones, recently discovered plant hormones, inhibit:
A Primary root elongation by suppressing meristematic cell division at the root tipB Shoot branching (axillary bud outgrowth) and promote mycorrhizal symbiosisC Seed germination in the surrounding rhizosphere soil communityD Stomatal opening by maintaining elevated guard cell turgor pressureShow answer & explanation →
Q62.
The 'triple response' of pea seedlings (reduced stem elongation, increased stem thickening, and horizontal growth) is a classic bioassay for which plant hormone?
A GibberellinB EthyleneC AuxinD CytokininShow answer & explanation →
Q63.
Abscisic acid is often called a 'stress hormone' in plants mainly because it:
A Promotes stomatal closure and dormancy in response to water stressB Stimulates seed germination under high humidity conditionsC Promotes flowering specifically in response to cold temperaturesD Promotes rapid cell elongation under conditions of high water availabilityShow answer & explanation →
Q64.
Auxin transport within plant tissues is largely polar (mainly basipetal in stems), a property explained by:
A Auxin's inability to cross the plasma membrane in either directionB Auxin being synthesized only at the base of the stemC Asymmetric distribution of auxin efflux carriers (PIN proteins) on the cell membraneD Passive diffusion alone, without involvement of any membrane transport proteinsShow answer & explanation →
Q65.
Gibberellins promote bolting (rapid internode elongation) in rosette plants mainly by:
A Inhibiting cell division in the apical meristem entirelyB Stimulating cell elongation and division in the stem internodesC Causing abscission of the existing leaves on the rosetteD Triggering immediate seed dormancy in the same plantShow answer & explanation →
Q66.
The dependence of flowering on the relative lengths of day and night is called:
A photoperiodismB vernalisationC phototropismD dormancyShow answer & explanation →
Q67.
Plants that flower only when the day length is shorter than a critical value are:
A short-day plantsB long-day plantsC day-neutral plantsD aquatic plantsShow answer & explanation →
Q68.
The hormone applied to stem cuttings to promote the growth of roots is:
A auxinB ethyleneC abscisic acidD florigenShow answer & explanation →
Q69.
The plant "stress hormone" that helps plants tolerate drought is:
A abscisic acidB plain auxinC plain gibberellinD plain cytokininShow answer & explanation →
Q70.
Gibberellins can cause dwarf plants to grow ___ by lengthening the internodes:
A tallerB shorterC bushierD flatterShow answer & explanation →
Q71.
Leaf fall (abscission) is promoted by ethylene together with:
A abscisic acidB plain auxinC plain cytokininD plain gibberellinShow answer & explanation →
Q72.
The growth of a pollen tube toward the ovule in response to chemicals is an example of:
A chemotropismB phototropismC geotropismD thigmotropismShow answer & explanation →
Q73.
The region just behind the root tip where cells lengthen is the zone of:
A elongationB maturationC divisionD dormancyShow answer & explanation →
Q74.
Cytokinins delay the ageing of leaves, an action known as the ___ effect:
A anti-senescenceB the ripeningC the dormancyD the wiltingShow answer & explanation →
Q75.
The whole series of changes from a seed to a mature, reproducing plant is called:
A developmentB transpirationC respirationD excretionShow answer & explanation →