Chapter 11: Transport in Plants – MCQs
🌱 Transport in Plants – MCQs
Part 1 (Q1–Q25)
Q1. The main solvent in plant transport is
A) Alcohol
B) Water ✅
C) Glucose
D) Amino acids
Explanation: Water is the universal solvent; transport of minerals, sugars, and hormones depends on it.
Q2. The process of diffusion requires
A) ATP
B) Carrier proteins
C) Concentration gradient ✅
D) Light
Explanation: Diffusion is passive, driven by concentration gradient, no ATP required.
Q3. The net movement of molecules is from
A) Higher to lower concentration ✅
B) Lower to higher concentration
C) Equal to equal concentration
D) Random
Explanation: Diffusion occurs down the concentration gradient.
Q4. The diffusion of water across a semipermeable membrane is called
A) Filtration
B) Osmosis ✅
C) Imbibition
D) Transpiration
Explanation: Osmosis = passive movement of water across a semipermeable membrane.
Q5. Which solution has higher water potential?
A) Pure water ✅
B) Sugar solution
C) Salt solution
D) Acidic solution
Explanation: Pure water has maximum water potential (Ψ = 0).
Q6. The pressure exerted by plasma membrane against the cell wall is
A) Wall pressure
B) Turgor pressure ✅
C) Diffusion pressure
D) Osmotic pressure
Explanation: Turgor pressure maintains rigidity of plant cells.
Q7. Loss of water through cuticle is
A) Guttation
B) Cuticular transpiration ✅
C) Lenticular transpiration
D) Stomatal transpiration
Explanation: Cuticular transpiration occurs through waxy cuticle (minor compared to stomatal).
Q8. The major pathway of water loss in plants is
A) Lenticular transpiration
B) Stomatal transpiration ✅
C) Cuticular transpiration
D) Guttation
Explanation: Stomatal transpiration accounts for 90–95% of total water loss.
Q9. The loss of water as droplets from leaf margins is
A) Transpiration
B) Guttation ✅
C) Osmosis
D) Diffusion
Explanation: Guttation occurs through hydathodes due to root pressure.
Q10. The pressure generated in xylem due to active water absorption is
A) Root pressure ✅
B) Turgor pressure
C) Osmotic pressure
D) Capillary action
Explanation: Root pressure is positive hydrostatic pressure in xylem.
Q11. The main force for upward movement of water in tall trees is
A) Root pressure
B) Capillarity
C) Transpiration pull ✅
D) Osmosis
Explanation: Transpiration pull + cohesion-tension mechanism explains water ascent.
Q12. The Cohesion-tension theory was proposed by
A) Darwin
B) Dixon and Joly ✅
C) Münch
D) Haberlandt
Explanation: Dixon and Joly (1894) proposed the cohesion-tension theory.
Q13. The translocation of food in plants occurs through
A) Xylem
B) Phloem ✅
C) Cortex
D) Epidermis
Explanation: Phloem transports sucrose, amino acids, and hormones bidirectionally.
Q14. The Pressure-flow hypothesis was proposed by
A) Dixon and Joly
B) Münch ✅
C) Strasburger
D) Priestley
Explanation: Münch (1930) explained phloem transport as mass flow hypothesis.
Q15. Xylem transports
A) Water and minerals ✅
B) Sugars only
C) Amino acids
D) Hormones
Explanation: Xylem transports water + minerals unidirectionally.
Q16. Phloem transports
A) Water
B) Minerals
C) Organic food ✅
D) Ions only
Explanation: Phloem transports sucrose and other organic solutes both ways.
Q17. The main form of sugar translocated in phloem is
A) Glucose
B) Fructose
C) Sucrose ✅
D) Maltose
Explanation: Sucrose is the main transport sugar in plants.
Q18. In translocation, loading of sucrose occurs in
A) Source cells ✅
B) Sink cells
C) Root hairs
D) Hydathodes
Explanation: Source cells (leaves) load sucrose into phloem actively.
Q19. The apoplast pathway involves
A) Cytoplasm
B) Vacuole
C) Cell walls and intercellular spaces ✅
D) Nucleus
Explanation: Apoplast pathway = transport through cell walls without crossing membranes.
Q20. The symplast pathway involves
A) Cell walls
B) Vacuole
C) Cytoplasm connected by plasmodesmata ✅
D) Cuticle
Explanation: Symplast pathway = cytoplasmic route via plasmodesmata.
Q21. Which is faster: apoplast or symplast pathway?
A) Symplast
B) Apoplast ✅
C) Both equal
D) None
Explanation: Apoplast transport is faster as it doesn’t cross membranes.
Q22. Endosmosis occurs when
A) Cell placed in hypertonic solution
B) Cell placed in hypotonic solution ✅
C) Cell in isotonic solution
D) Cell in concentrated sugar solution
Explanation: Hypotonic solution → water enters cell → endosmosis.
Q23. Plasmolysis occurs when
A) Cell in hypotonic solution
B) Cell in hypertonic solution ✅
C) Cell in isotonic solution
D) Cell in pure water
Explanation: Hypertonic solution → water exits → cell shrinks (plasmolysis).
Q24. Imbibition is
A) Uptake of water by osmosis
B) Uptake of water by hydrophilic colloids ✅
C) Diffusion of gases
D) Root absorption
Explanation: Imbibition = absorption of water by colloids like starch, cellulose.
Q25. The water potential of pure water is
A) +1000
B) –1000
C) Zero ✅
D) One
Explanation: By definition, Ψ of pure water at standard conditions = 0.
🌱 Plant Physiology – Transport in Plants
Part 2 (Q26–Q50)
Q26. The Casparian strip is found in
A) Epidermis
B) Endodermis ✅
C) Cortex
D) Pericycle
Explanation: Casparian strip is a band of suberin in endodermis, regulating water entry into stele.
Q27. Which pathway is blocked by the Casparian strip?
A) Symplast
B) Apoplast ✅
C) Both symplast and apoplast
D) Transpiration
Explanation: Casparian strip blocks apoplast pathway, forcing water into symplast.
Q28. The main driving force for translocation in phloem is
A) ATP hydrolysis
B) Osmotic pressure gradient ✅
C) Root pressure
D) Active transport of K⁺ ions
Explanation: Münch hypothesis: phloem transport occurs via pressure/osmotic gradient.
Q29. Transport proteins in membranes help in
A) Active transport ✅
B) Osmosis
C) Imbibition
D) Diffusion only
Explanation: Transport proteins are essential for active and facilitated transport.
Q30. Which type of transport is uphill (against gradient)?
A) Passive diffusion
B) Facilitated diffusion
C) Active transport ✅
D) Osmosis
Explanation: Active transport uses ATP to move solutes against concentration gradient.
Q31. Facilitated diffusion differs from active transport in being
A) Energy-dependent
B) Downhill ✅
C) Against gradient
D) Endergonic
Explanation: Facilitated diffusion uses carrier proteins but no ATP (downhill).
Q32. The transpiration pull is generated due to
A) Osmosis
B) Cohesion and adhesion of water ✅
C) Root pressure only
D) Capillary action
Explanation: Cohesion + adhesion + transpiration generate negative pressure for water ascent.
Q33. Which factor increases the rate of transpiration?
A) High humidity
B) High temperature ✅
C) High CO₂
D) Darkness
Explanation: High temperature increases evaporation, thus transpiration.
Q34. Which factor reduces transpiration?
A) Wind
B) High humidity ✅
C) Sunlight
D) Temperature rise
Explanation: High humidity decreases water potential gradient → reduces transpiration.
Q35. Which ion plays a major role in stomatal opening?
A) Na⁺
B) K⁺ ✅
C) Ca²⁺
D) Mg²⁺
Explanation: Potassium ion (K⁺) accumulation in guard cells leads to stomatal opening.
Q36. Stomata open in light due to
A) Loss of K⁺
B) Uptake of K⁺ ✅
C) Loss of water
D) Active pumping of Na⁺
Explanation: In light, K⁺ ions enter guard cells, water follows osmotically → opening.
Q37. In CAM plants, stomata open during
A) Day
B) Night ✅
C) Both
D) Never
Explanation: CAM plants (cacti, succulents) open stomata at night to minimize water loss.
Q38. Which theory explains ascent of sap in tall trees?
A) Pressure-flow theory
B) Cohesion-tension theory ✅
C) Capillary theory
D) Root pressure theory
Explanation: Cohesion-tension theory is widely accepted for water transport.
Q39. Root pressure is maximum during
A) Night ✅
B) Day
C) Afternoon
D) Evening
Explanation: Root pressure develops mostly at night when transpiration is low.
Q40. The maximum root pressure recorded is about
A) 1 atm
B) 2 atm
C) 5 atm ✅
D) 20 atm
Explanation: Maximum root pressure is ~5 atm, insufficient alone for tall trees.
Q41. Which plant part shows the first response to water stress?
A) Leaves ✅
B) Roots
C) Stem
D) Flowers
Explanation: Leaves lose turgor pressure first and close stomata under water stress.
Q42. Transpiration helps in
A) Absorption of CO₂
B) Ascent of sap ✅
C) Transport of sucrose
D) ATP synthesis
Explanation: Transpiration pull is the main force for upward water transport.
Q43. The transpirational water loss in plants is
A) 1–5%
B) 10–20%
C) More than 90% ✅
D) Less than 1%
Explanation: Over 90% of absorbed water is lost by transpiration.
Q44. The main site of guttation is
A) Stomata
B) Hydathodes ✅
C) Lenticels
D) Trichomes
Explanation: Hydathodes at leaf margins secrete water droplets by guttation.
Q45. Lenticels help in
A) Photosynthesis
B) Transpiration (lenticellular) ✅
C) Absorption
D) Nitrogen fixation
Explanation: Lenticels allow gas exchange and minor water loss (lenticellular transpiration).
Q46. The cohesion of water molecules is due to
A) Ionic bonds
B) Hydrogen bonds ✅
C) Covalent bonds
D) Hydrophobic interactions
Explanation: Hydrogen bonding between water molecules gives cohesion.
Q47. The osmotic potential of a solution is always
A) Positive
B) Negative ✅
C) Zero
D) Variable
Explanation: Osmotic potential (Ψs) is always negative compared to pure water (Ψ = 0).
Q48. The pressure exerted by cell wall against turgor pressure is
A) Osmotic pressure
B) Wall pressure ✅
C) Diffusion pressure
D) Root pressure
Explanation: Wall pressure balances turgor pressure in plant cells.
Q49. If a cell is placed in hypertonic solution, it will
A) Become turgid
B) Plasmolyze ✅
C) Burst
D) Divide
Explanation: In hypertonic solution, water exits → cell shrinks (plasmolysis).
Q50. If a plasmolyzed cell is placed in hypotonic solution, it
A) Dies
B) Remains plasmolyzed
C) Becomes turgid again (deplasmolysis) ✅
D) Bursts
Explanation: Deplasmolysis occurs when water enters again → cell becomes turgid.
🌱 Plant Physiology – Transport in Plants
Part 3 (Q51–Q75)
Q51. The driving force for water absorption by roots is
A) Osmotic gradient ✅
B) Root pressure
C) Transpiration pull
D) Wall pressure
Explanation: Water enters roots primarily by osmosis due to solute gradient.
Q52. Water is pulled upward in xylem mainly due to
A) Capillarity
B) Root pressure
C) Transpiration pull ✅
D) Osmotic pressure
Explanation: Transpiration pull and cohesion–tension mechanism drive water ascent.
Q53. Which experiment demonstrated root pressure?
A) Ringing experiment
B) Porometer experiment
C) Exudation from cut stem ✅
D) Ganong’s potometer
Explanation: Exudation from cut stem in the morning indicates root pressure.
Q54. Ganong’s potometer measures
A) Osmosis
B) Guttation
C) Rate of transpiration ✅
D) Photosynthesis
Explanation: Potometer measures transpiration rate by water uptake.
Q55. Which factor closes stomata?
A) Blue light
B) Low CO₂
C) Water stress ✅
D) K⁺ influx
Explanation: Under water stress, stomata close to reduce water loss.
Q56. Antitranspirants reduce
A) Root absorption
B) Transpiration ✅
C) Photosynthesis
D) Respiration
Explanation: Antitranspirants (e.g., phenyl mercuric acetate) lower transpiration rate.
Q57. Stomatal movement is regulated by
A) Nucleus
B) Guard cell turgor ✅
C) Cuticle
D) Xylem
Explanation: Guard cells swell/shrink to regulate stomatal aperture.
Q58. The protein responsible for water transport across membranes is
A) Tubulin
B) Aquaporin ✅
C) Actin
D) Myosin
Explanation: Aquaporins are channel proteins facilitating water transport.
Q59. The pressure–flow hypothesis explains
A) Ascent of sap
B) Translocation of sugars ✅
C) Transpiration
D) Root pressure
Explanation: Münch’s pressure–flow hypothesis explains phloem transport of food.
Q60. Source to sink movement in phloem means
A) Roots → leaves
B) Leaves → growing organs ✅
C) Soil → roots
D) Xylem → stem
Explanation: Sugars move from source (leaves) to sink (roots, fruits, flowers).
Q61. Which element plays key role in osmotic regulation of guard cells?
A) Na⁺
B) K⁺ ✅
C) Cl⁻
D) Mg²⁺
Explanation: K⁺ ions regulate turgidity of guard cells → stomatal movement.
Q62. In plants, minerals are absorbed by roots mainly through
A) Diffusion
B) Active transport ✅
C) Osmosis
D) Imbibition
Explanation: Minerals are absorbed against concentration gradient using ATP.
Q63. Apoplastic movement is interrupted at
A) Epidermis
B) Casparian strip of endodermis ✅
C) Cortex
D) Pericycle
Explanation: Casparian strip forces water into symplast before entering xylem.
Q64. Cohesion–tension theory depends on
A) Root hairs
B) Hydrogen bonding in water ✅
C) Cell wall pressure
D) Lignified xylem
Explanation: Hydrogen bonds between water molecules provide cohesion.
Q65. The rate of transpiration is measured using
A) Ganong’s respirometer
B) Ganong’s potometer ✅
C) Porometer
D) Hygrometer
Explanation: Potometer measures water uptake ~ transpiration rate.
Q66. Root pressure is not sufficient in
A) Small herbs
B) Tall trees ✅
C) Seedlings
D) Aquatic plants
Explanation: Root pressure is too weak to explain water rise in tall trees.
Q67. The apoplast constitutes
A) Protoplasm
B) Cell wall + intercellular spaces ✅
C) Cytoplasm
D) Vacuole
Explanation: Apoplast = non-living continuum of cell walls and spaces.
Q68. The symplast constitutes
A) Cell walls
B) Cytoplasm interconnected by plasmodesmata ✅
C) Vacuoles
D) Xylem
Explanation: Symplast is living continuum via plasmodesmata.
Q69. Xylem sap mainly contains
A) Sugars
B) Mineral salts ✅
C) Lipids
D) Amino acids
Explanation: Xylem sap = water + dissolved mineral salts.
Q70. Phloem sap mainly contains
A) Mineral salts
B) Sucrose ✅
C) Proteins only
D) Water only
Explanation: Sucrose is main sugar translocated in phloem.
Q71. The rate of translocation in phloem is
A) 1 cm/hr
B) 1 m/hr ✅
C) 1 mm/hr
D) 10 m/hr
Explanation: Phloem translocation speed ~1 m/hr, much faster than diffusion.
Q72. The process of guttation is due to
A) Transpiration
B) Root pressure ✅
C) Capillarity
D) Osmosis
Explanation: Root pressure forces water out as droplets via hydathodes.
Q73. Transpiration serves to
A) Reduce CO₂
B) Cool leaves ✅
C) Synthesize ATP
D) Form glucose
Explanation: Transpiration cools leaves and maintains water flow.
Q74. Which structure prevents collapse of xylem under tension?
A) Casparian strip
B) Lignified walls ✅
C) Guard cells
D) Cuticle
Explanation: Lignin strengthens xylem walls, preventing collapse.
Q75. Which factor directly controls stomatal movement?
A) Guard cell turgor ✅
B) Cuticle thickness
C) Root pressure
D) Light intensity only
Explanation: Guard cell turgor is the immediate regulator of stomatal opening/closure.
🌱 Plant Physiology – Transport in Plants
Part 4 (Q76–Q100)
Q76. The water potential of a solution becomes
A) More positive when solutes are added
B) More negative when solutes are added ✅
C) Zero when solutes are added
D) Independent of solutes
Explanation: Solutes lower free energy of water, making Ψs negative.
Q77. The unit of water potential is
A) Joule
B) Bar / MPa ✅
C) Pascal only
D) Liter
Explanation: Water potential is expressed in pressure units (bars/MPa).
Q78. The pressure potential in a fully turgid cell is
A) Zero
B) Positive ✅
C) Negative
D) Always constant
Explanation: Turgid cells exert positive pressure potential (Ψp).
Q79. Osmotic potential is also called
A) Pressure potential
B) Solute potential ✅
C) Turgor potential
D) Water potential
Explanation: Ψs = solute (osmotic) potential, always negative.
Q80. The symplast pathway is slower than apoplast because
A) It involves cytoplasmic streaming ✅
B) It uses diffusion
C) It occurs via cell walls
D) It bypasses plasmodesmata
Explanation: Symplast transport is slower as solutes move through cytoplasm & plasmodesmata.
Q81. The maximum transpiration occurs from
A) Upper epidermis
B) Lower epidermis ✅
C) Stem surface
D) Cuticle
Explanation: Lower epidermis has more stomata → higher transpiration.
Q82. The opening and closing of stomata is controlled by
A) Guard cell turgor ✅
B) Mesophyll cells
C) Root hairs
D) Xylem
Explanation: Guard cell swelling/shrinking regulates stomata.
Q83. Which plant shows CAM photosynthesis to conserve water?
A) Maize
B) Cactus ✅
C) Wheat
D) Rice
Explanation: Cactus uses CAM metabolism, opening stomata at night.
Q84. Wilting is due to
A) High root pressure
B) Excessive transpiration ✅
C) Water uptake
D) Mineral deficiency only
Explanation: Excessive transpiration > absorption → water loss → wilting.
Q85. The closing of stomata under water stress is caused by
A) Increase in auxin
B) Abscisic acid (ABA) ✅
C) Gibberellins
D) Cytokinins
Explanation: ABA is a stress hormone, closes stomata to prevent water loss.
Q86. Root hair zone is important for
A) Conduction
B) Absorption of water ✅
C) Photosynthesis
D) Storage
Explanation: Root hair zone increases surface area for water/mineral absorption.
Q87. Which tissue is responsible for upward conduction of water?
A) Phloem
B) Xylem ✅
C) Cambium
D) Pericycle
Explanation: Xylem conducts water/minerals from roots to aerial parts.
Q88. The diffusion of water vapour from leaf to atmosphere is
A) Osmosis
B) Transpiration ✅
C) Guttation
D) Imbibition
Explanation: Transpiration is the diffusion of water vapour out of leaves.
Q89. The pressure that helps in phloem transport is
A) Root pressure
B) Turgor pressure ✅
C) Osmotic pressure
D) Wall pressure
Explanation: Turgor pressure difference between source and sink drives phloem transport.
Q90. The translocation in phloem is mainly
A) Unidirectional
B) Bidirectional ✅
C) Downward only
D) Upward only
Explanation: Phloem transport occurs from source → sink, which can be in both directions.
Q91. Xylem transport is always
A) Bidirectional
B) Upward (unidirectional) ✅
C) Downward only
D) Random
Explanation: Water and minerals move upward in xylem.
Q92. The transport of food is mainly in the form of
A) Glucose
B) Sucrose ✅
C) Fructose
D) Starch
Explanation: Sucrose is the translocated sugar in phloem.
Q93. When a plant cell is placed in isotonic solution
A) Water enters
B) Water exits
C) No net water movement ✅
D) Cell bursts
Explanation: In isotonic solution, osmotic potentials are equal → no net flow.
Q94. DPD (Diffusion Pressure Deficit) is equal to
A) Osmotic pressure – turgor pressure ✅
B) Turgor pressure + osmotic pressure
C) Pressure potential – osmotic pressure
D) Osmotic pressure × wall pressure
Explanation: DPD = OP – TP, driving force for water entry.
Q95. The absorption of minerals against gradient requires
A) Passive diffusion
B) Active transport ✅
C) Osmosis
D) Facilitated diffusion
Explanation: Mineral uptake often requires ATP-driven active transport.
Q96. Stomata open due to
A) Influx of K⁺ ✅
B) Loss of K⁺
C) ABA increase
D) Decrease in turgor
Explanation: K⁺ entry → water influx → guard cells swell → stomata open.
Q97. The closure of stomata is associated with
A) Loss of K⁺ ✅
B) Influx of K⁺
C) High turgor
D) Low ABA
Explanation: K⁺ efflux → water exits → guard cells shrink → stomata close.
Q98. Which one is NOT a pathway for water movement in roots?
A) Apoplast
B) Symplast
C) Transmembrane
D) Phloem pathway ✅
Explanation: Water moves by apoplast, symplast, and transmembrane routes, not phloem.
Q99. Guttation is more common in
A) Herbs ✅
B) Tall trees
C) Desert shrubs
D) Conifers
Explanation: Herbaceous plants with hydathodes show guttation more often.
Q100. The ascent of sap in tall trees is mainly explained by
A) Root pressure
B) Capillarity
C) Cohesion–tension theory ✅
D) Imbibition
Explanation: Cohesion–tension + transpiration pull is the accepted mechanism in tall trees.
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