Plant Growth and Development - Practice Questions with Answers

Q1.

Gibberellins promote:

• A Adventitious root initiation exclusively, with no effect on shoot tissue
• B Stomatal closure via guard cell turgor loss under water stress
• C Stem elongation and seed germination
• D Climacteric fruit ripening through ethylene biosynthesis induction

Q2.

Auxin promotes:

• A Cell elongation and phototropism
• B Cell division at root tip
• C Leaf senescence
• D Stomatal closure

Q3.

Ethylene is a plant hormone involved in:

• A Stem elongation driven by cell wall loosening at the apical meristem
• B Fruit ripening and abscission
• C Adventitious root formation at the cut ends of stem cuttings
• D Directional bending of shoots toward a unidirectional light source

Q4.

ABA (Abscisic acid) causes:

• A Rapid stem elongation and internode growth
• B Triggering of seed germination processes
• C Stomatal closure and dormancy
• D Acceleration of fruit ripening and softening

Q5.

Apical dominance in plants is regulated by:

• A Gibberellins diffusing downward from the shoot apex to suppress lateral buds
• B Cytokinins transported upward from the root tip through the xylem stream
• C Auxin (IAA) from apical bud
• D Ethylene accumulating locally at axillary bud junctions

Q6.

Cytokinins, a class of plant hormones, mainly promote:

• A Stomatal closure
• B Stem elongation
• C Cell division
• D Fruit ripening

Q7.

Which plant hormone is commonly associated with promoting fruit ripening?

• A Ethylene
• B Gibberellin
• C Auxin
• D Cytokinin

Q8.

The bending of a plant shoot toward light is an example of:

• A Geotropism
• B Thigmotropism
• C Hydrotropism
• D Phototropism

Q9.

Seed dormancy in many plants helps ensure that:

• A Seeds germinate immediately after dispersal regardless of conditions
• B Germination occurs only under favourable environmental conditions
• C Germination always requires artificial chemical treatment
• D Seeds lose viability shortly after they are formed

Q10.

Differentiation in plant development refers to the process by which:

• A Mature cells revert back to a dividing meristematic state
• B Cells derived from meristems mature to perform specific functions
• C Plant organs increase only in number, not in specialization
• D Cells divide repeatedly without any change in structure

Q11.

The permanent, irreversible increase in the size of a plant is called:

• A growth
• B respiration
• C transpiration
• D digestion

Q12.

The region of active, continuous cell division in a plant is the:

• A meristem
• B cortex
• C pith
• D epidermis

Q13.

The chemical substances that regulate plant growth are called:

• A plant hormones
• B only enzymes
• C simple vitamins
• D soil minerals

Q14.

The hormone that promotes cell elongation and shoot growth is:

• A auxin
• B abscisic acid
• C ethylene
• D florigen

Q15.

The plant hormone responsible for fruit ripening is:

• A ethylene
• B auxin
• C cytokinin
• D gibberellin

Q16.

The plant hormone that promotes cell division is:

• A cytokinin
• B abscisic acid
• C ethylene
• D florigen

Q17.

Growth in a plant occurs mainly at the:

• A tips of roots and shoots
• B the middle of the old stem
• C the fully grown old leaves
• D the outer woody bark

Q18.

The bending of a plant shoot toward a source of light is called:

• A phototropism
• B geotropism
• C hydrotropism
• D thigmotropism

Q19.

The downward growth of roots in response to gravity is called:

• A geotropism
• B phototropism
• C hydrotropism
• D chemotropism

Q20.

The process by which a seed grows into a seedling is called:

• A germination
• B pollination
• C transpiration
• D respiration

Q21.

Vernalization is:

• A A plant's photoperiodic response to the relative length of day versus night
• B Requirement for cold treatment to induce flowering
• C Application of elevated temperature treatment to accelerate vegetative growth
• D Prolonged exposure to drought stress that triggers stomatal closure

Q22.

Cytokinin promotes:

• A Stem elongation by loosening cell walls at the subapical meristem
• B Cell division and delays senescence
• C Climacteric fruit ripening coupled with ethylene release
• D Primary root elongation exclusively, with no effect on lateral shoots

Q23.

Senescence in leaves is triggered by:

• A A sharp rise in cytokinin levels delivered from the root system
• B Decreased auxin and increased ethylene and ABA
• C An isolated drop in ambient temperature unaccompanied by hormonal change
• D An increase in available soil water supply to the root system

Q24.

Phytochrome is a photoreceptor that responds to:

• A Blue light exclusively, detected through a flavin chromophore
• B Red and far-red light (Pr and Pfr forms)
• C Ultraviolet light absorbed by UVR8 photoreceptor proteins
• D Green light wavelengths absorbed by chlorophyll-associated pigments

Q25.

Photoperiodism refers to:

• A The overall rate of carbon fixation occurring during daylight hours
• B Response of plants to the relative lengths of day and night for flowering
• C Light-induced changes in chlorophyll concentration affecting leaf color
• D Rapid guard cell turgor changes that open stomata at sunrise

Q26.

Auxin transport is primarily:

• A Acropetal, moving upward from the root tip toward the shoot apex
• B Polar (from shoot apex downward, basipetal)
• C Non-directional, diffusing randomly through ground tissue without polarity
• D Confined entirely to root tissue, absent from the shoot system

Q27.

Gravitropism in roots is caused by:

• A Auxin accumulating on the upper side, accelerating elongation there instead
• B Auxin accumulating on the lower side, inhibiting root elongation there
• C Uniform auxin distribution across the root cap with no lateral asymmetry
• D Cytokinin redistribution within statocytes sensing the gravity vector

Q28.

Apical dominance, in which a growing apical bud suppresses the growth of lateral buds, is mainly caused by:

• A Ethylene released from leaves undergoing senescence
• B Gibberellin transported upward from the root system
• C High auxin levels produced by the apical bud itself
• D Cytokinin moving downward from the shoot tip

Q29.

Abscisic acid is often referred to as a stress hormone in plants because it:

• A Induces stomatal closure and seed dormancy under stress like drought
• B Stimulates internode elongation within the stem under usual circumstances
• C Promotes faster cell division in favourable conditions as generally observed
• D Speeds up fruit ripening together with ethylene in typical laboratory settings

Q30.

Ethylene's effect in promoting fruit ripening is widely exploited commercially because it:

• A Promotes ongoing vegetative growth of the fruit as widely reported
• B Stops sugar formation within the ripening fruit according to most studies
• C Triggers starch-to-sugar conversion and softening of fruit tissue
• D Halts respiration within the ripening fruit cells in the majority of documented cases

Q31.

The hormone that promotes stomatal closure and maintains seed dormancy is:

• A abscisic acid
• B plain auxin
• C plain cytokinin
• D plain gibberellin

Q32.

The hormone that breaks seed dormancy and promotes stem elongation is:

• A gibberellin
• B abscisic acid
• C ethylene
• D florigen

Q33.

The stage of growth in which cells rapidly enlarge is the ___ phase:

• A elongation
• B meristematic
• C maturation
• D dormancy

Q34.

Apical dominance, in which the main shoot suppresses side shoots, is caused by:

• A auxin
• B ethylene
• C abscisic acid
• D florigen

Q35.

The directional growth of a tendril in response to touch is called:

• A thigmotropism
• B phototropism
• C geotropism
• D hydrotropism

Q36.

A graph of growth against time typically gives a ___ curve:

• A sigmoid (S-shaped)
• B a straight-line
• C a circular one
• D a zigzag one

Q37.

Differentiation is the process by which cells become ___ for particular functions:

• A specialised
• B identical
• C smaller
• D non-living

Q38.

Auxin is produced mainly at the:

• A shoot tip
• B only the root cap
• C old leaves
• D outer bark

Q39.

The directional growth of a plant part in response to a stimulus is called a:

• A tropism
• B nastic movement
• C nerve reflex
• D circulation

Q40.

Vernalisation is the promotion of flowering by exposure to:

• A low temperature
• B high light
• C severe drought
• D strong heat

Q41.

Florigen is now identified as:

• A A specialized auxin derivative synthesized directly within the shoot apical meristem region
• B FT protein (Flowering Locus T) produced in leaves, transported to shoot apex via phloem
• C Gibberellin A3 synthesized locally within developing floral primordia tissue
• D A cytokinin variant transported acropetally upward from the root system below

Q42.

Jasmonates (jasmonic acid) are plant hormones that:

• A Promote climacteric fruit ripening mainly through ethylene synergism during late development according to standard textbooks
• B Activate defense responses against herbivory and pathogens, regulate pollen development, and inhibit growth
• C Promote stomatal opening by activating proton pumps within guard cell membranes directly in general practice
• D Bind the same TIR1 receptor as auxin and trigger largely identical downstream signaling pathways as frequently described

Q43.

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 settings
• B FLC (Flowering Locus C) - a repressor of flowering - silenced by vernalization through polycomb-mediated H3K27me3 marking
• C Gibberellin signaling acting mainly alone through the DELLA degradation pathway each time under usual circumstances
• D Mainly transcriptional control with little chromatin-level modification involved overall according to most researchers

Q44.

Calmodulin in plant signal transduction:

• A Functions as a receptor tyrosine kinase embedded directly in the plasma membrane structure under most conditions encountered
• B Is a calcium sensor that, when Ca²⁺ 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 practice
• D Is itself a diffusible plant hormone synthesized within the shoot apex region in many documented cases

Q45.

Phytochrome-interacting factors (PIFs) are:

• A Red light receptors themselves, which absorb photons directly through a bound chromophore group structure according to conventional understanding
• B Transcription factors that interact with Pfr form of phytochrome and are degraded upon light activation, derepressing light-responsive genes
• C Plastid-localized enzymes responsible for synthesizing the phytochrome chromophore precursor molecule in routine practice overall in most cases
• D DNA repair proteins that are activated specifically in response to ultraviolet light exposure events under typical conditions according to standard textbooks

Q46.

Strigolactones, recently discovered plant hormones, inhibit:

• A Primary root elongation by suppressing meristematic cell division at the root tip
• B Shoot branching (axillary bud outgrowth) and promote mycorrhizal symbiosis
• C Seed germination in the surrounding rhizosphere soil community
• D Stomatal opening by maintaining elevated guard cell turgor pressure

Q47.

The 'triple response' of pea seedlings (reduced stem elongation, increased stem thickening, and horizontal growth) is a classic bioassay for which plant hormone?

• A Gibberellin
• B Ethylene
• C Auxin
• D Cytokinin

Q48.

Abscisic acid is often called a 'stress hormone' in plants mainly because it:

• A Promotes stomatal closure and dormancy in response to water stress
• B Stimulates seed germination under high humidity conditions
• C Promotes flowering specifically in response to cold temperatures
• D Promotes rapid cell elongation under conditions of high water availability

Q49.

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 direction
• B Auxin being synthesized only at the base of the stem
• C Asymmetric distribution of auxin efflux carriers (PIN proteins) on the cell membrane
• D Passive diffusion alone, without involvement of any membrane transport proteins

Q50.

Gibberellins promote bolting (rapid internode elongation) in rosette plants mainly by:

• A Inhibiting cell division in the apical meristem entirely
• B Stimulating cell elongation and division in the stem internodes
• C Causing abscission of the existing leaves on the rosette
• D Triggering immediate seed dormancy in the same plant

Q51.

The dependence of flowering on the relative lengths of day and night is called:

• A photoperiodism
• B vernalisation
• C phototropism
• D dormancy

Q52.

Plants that flower only when the day length is shorter than a critical value are:

• A short-day plants
• B long-day plants
• C day-neutral plants
• D aquatic plants

Q53.

The hormone applied to stem cuttings to promote the growth of roots is:

• A auxin
• B ethylene
• C abscisic acid
• D florigen

Q54.

The plant "stress hormone" that helps plants tolerate drought is:

• A abscisic acid
• B plain auxin
• C plain gibberellin
• D plain cytokinin

Q55.

Gibberellins can cause dwarf plants to grow ___ by lengthening the internodes:

• A taller
• B shorter
• C bushier
• D flatter

Q56.

Leaf fall (abscission) is promoted by ethylene together with:

• A abscisic acid
• B plain auxin
• C plain cytokinin
• D plain gibberellin

Q57.

The growth of a pollen tube toward the ovule in response to chemicals is an example of:

• A chemotropism
• B phototropism
• C geotropism
• D thigmotropism

Q58.

The region just behind the root tip where cells lengthen is the zone of:

• A elongation
• B maturation
• C division
• D dormancy

Q59.

Cytokinins delay the ageing of leaves, an action known as the ___ effect:

• A anti-senescence
• B the ripening
• C the dormancy
• D the wilting

Q60.

The whole series of changes from a seed to a mature, reproducing plant is called:

• A development
• B transpiration
• C respiration
• D excretion