1. The movement of molecules from a region of higher concentration to lower concentration is called:
A) Osmosis
B) Diffusion
C) Active transport
D) Imbibition
Answer: B) Diffusion
Explanation: Diffusion is a passive movement of molecules along the concentration gradient.
2. The movement of water through a semi-permeable membrane is called:
A) Diffusion
B) Osmosis
C) Imbibition
D) Transpiration
Answer: B) Osmosis
Explanation: Osmosis is the passive diffusion of water molecules across a semipermeable membrane.
3. Imbibition is important in:
A) Root elongation
B) Seed germination
C) Photosynthesis
D) Transpiration
Answer: B) Seed germination
Explanation: Dry seeds imbibe water due to hydrophilic colloids in seed coats, initiating germination.
4. A solution with lower solute concentration compared to another is called:
A) Isotonic
B) Hypotonic
C) Hypertonic
D) None of these
Answer: B) Hypotonic
Explanation: In hypotonic solutions, water moves into cells causing swelling.
5. Plasmolysis occurs when a cell is placed in:
A) Hypotonic solution
B) Isotonic solution
C) Hypertonic solution
D) Distilled water
Answer: C) Hypertonic solution
Explanation: Water moves out of the cell, protoplast shrinks away from cell wall.
6. The pressure responsible for water absorption in roots is:
A) Root pressure
B) Osmotic pressure
C) Turgor pressure
D) Diffusion pressure
Answer: A) Root pressure
Explanation: Root pressure develops due to osmotic uptake of water in xylem.
7. Which instrument is used to study plasmolysis?
A) Simple microscope
B) Compound microscope
C) Electron microscope
D) X-ray diffraction
Answer: B) Compound microscope
Explanation: Plasmolysis can be observed in epidermal peel cells under compound microscope.
8. When the cell wall resists further entry of water, the cell is said to be:
A) Flaccid
B) Turgid
C) Plasmolysed
D) Hypertonic
Answer: B) Turgid
Explanation: Turgid cells exert turgor pressure against the cell wall.
9. Water potential of pure water is:
A) 1
B) 0
C) –1
D) 100
Answer: B) 0
Explanation: Pure water has maximum water potential taken as zero.
10. Active transport in plants requires:
A) ATP energy
B) Osmosis
C) Diffusion
D) Imbibition
Answer: A) ATP energy
Explanation: Active transport moves molecules against concentration gradient using energy.
11. Symplastic movement of water occurs through:
A) Cell wall
B) Cytoplasm via plasmodesmata
C) Vacuole only
D) Xylem vessels only
Answer: B) Cytoplasm via plasmodesmata
Explanation: Symplast pathway involves protoplasmic continuum of adjacent cells.
12. Apoplastic movement of water occurs through:
A) Vacuoles
B) Cytoplasm
C) Cell walls and intercellular spaces
D) Plasmodesmata
Answer: C) Cell walls and intercellular spaces
Explanation: Apoplast is non-living pathway outside plasma membrane.
13. The symplastic pathway is interrupted by:
A) Xylem
B) Phloem
C) Casparian strips
D) Pith
Answer: C) Casparian strips
Explanation: Suberized Casparian strips block apoplastic flow in endodermis forcing symplastic entry.
14. The first step in water absorption by roots is:
A) Diffusion
B) Active transport
C) Osmosis
D) Imbibition
Answer: D) Imbibition
Explanation: Root hairs imbibe water before osmotic entry.
15. The term water potential was introduced by:
A) van’t Hoff
B) Slatyer & Taylor
C) Dixon & Joly
D) Strasburger
Answer: B) Slatyer & Taylor
Explanation: They introduced the concept of water potential in 1960s.
16. When a cell is in isotonic solution, its water potential is:
A) Higher than outside
B) Lower than outside
C) Equal to outside
D) Zero
Answer: C) Equal to outside
Explanation: In isotonic solution, no net water movement occurs.
17. Root pressure is maximum in:
A) Dry season
B) Early spring
C) Rainy season
D) Midday summer
Answer: B) Early spring
Explanation: Root pressure is high in spring when transpiration is low.
18. The swelling of wooden doors in rainy season is due to:
A) Osmosis
B) Imbibition
C) Diffusion
D) Capillarity
Answer: B) Imbibition
Explanation: Wood imbibes water and swells.
19. The units of water potential are:
A) Calories
B) Joules
C) Pascal (pressure units)
D) Litres
Answer: C) Pascal (pressure units)
Explanation: Water potential is expressed in pressure units (MPa).
20. The diffusion pressure deficit (DPD) is equivalent to:
A) Osmotic pressure – Turgor pressure
B) Osmotic pressure + Turgor pressure
C) Osmotic pressure – Wall pressure
D) Water potential × Turgor pressure
Answer: A) Osmotic pressure – Turgor pressure
Explanation: DPD = OP – TP; driving force for water absorption.
21. The entry of water into guard cells causing stomatal opening is due to:
A) Active transport of K⁺
B) Passive diffusion of CO₂
C) Plasmolysis
D) Protein synthesis
Answer: A) Active transport of K⁺
Explanation: K⁺ influx lowers water potential, water enters guard cells, stomata open.
22. Endosmosis occurs when a cell is placed in:
A) Hypotonic solution
B) Hypertonic solution
C) Isotonic solution
D) None of these
Answer: A) Hypotonic solution
Explanation: Water enters the cell, making it turgid.
23. Exosmosis occurs when a cell is placed in:
A) Hypotonic solution
B) Hypertonic solution
C) Isotonic solution
D) Distilled water
Answer: B) Hypertonic solution
Explanation: Water leaves the cell, leading to plasmolysis.
24. The movement of water from soil into xylem across cortex is mainly:
A) Apoplastic & Symplastic
B) Only active
C) Only through vacuoles
D) By guttation
Answer: A) Apoplastic & Symplastic
Explanation: Water moves via apoplast and symplast across root tissues.
25. In higher plants, water mainly moves upward through:
A) Phloem
B) Xylem
C) Cortex
D) Cambium
Answer: B) Xylem
Explanation: Xylem vessels and tracheids transport water and minerals.
Q26. The main region of water absorption in roots is:
A) Root cap
B) Meristematic zone
C) Zone of root hairs
D) Zone of elongation
Answer: C) Zone of root hairs
Explanation: Root hairs greatly increase surface area for water absorption.
27. Water absorption by roots is mostly:
A) Passive
B) Active
C) Imbibition
D) Endosmosis
Answer: A) Passive
Explanation: Most water uptake occurs due to transpiration pull (a passive process).
28. Root pressure is best demonstrated by:
A) Plasmolysis experiment
B) Guttation
C) Transpiration
D) Phototropism
Answer: B) Guttation
Explanation: Root pressure pushes water out through hydathodes at leaf tips, seen as guttation drops.
29. The ascent of sap in tall trees is best explained by:
A) Root pressure theory
B) Capillarity theory
C) Cohesion-tension theory
D) Imbibition theory
Answer: C) Cohesion-tension theory
Explanation: Dixon & Joly proposed that water rises due to transpiration pull and cohesion of water molecules.
30. Capillary theory is insufficient to explain ascent of sap because:
A) Water is not cohesive
B) Trees are tall (up to 100 m)
C) Root pressure is absent
D) It requires ATP
Answer: B) Trees are tall (up to 100 m)
Explanation: Capillary rise cannot explain movement of water beyond a few meters.
31. The cohesion-tension theory was proposed by:
A) Strasburger
B) Dixon & Joly
C) Bose
D) Priestley
Answer: B) Dixon & Joly
Explanation: They proposed this widely accepted theory in 1894.
32. Maximum transpiration occurs through:
A) Lenticels
B) Cuticle
C) Stomata
D) Hydathodes
Answer: C) Stomata
Explanation: Stomata account for ~90% of total transpiration.
33. The cuticular transpiration is minimum in:
A) Xerophytes
B) Hydrophytes
C) Mesophytes
D) Halophytes
Answer: A) Xerophytes
Explanation: Xerophytes have thick cuticles to reduce water loss.
34. The loss of water in liquid form through hydathodes is called:
A) Transpiration
B) Guttation
C) Exudation
D) Dew
Answer: B) Guttation
Explanation: Root pressure pushes liquid water through hydathodes.
35. Stomata open due to:
A) Loss of turgor in guard cells
B) Gain of turgor in guard cells
C) Photosynthesis in spongy cells
D) Root pressure
Answer: B) Gain of turgor in guard cells
Explanation: Turgid guard cells bend, opening stomatal pore.
36. Which factor closes stomata?
A) Blue light
B) Absorption of K⁺ by guard cells
C) Abscisic acid (ABA)
D) Photosynthesis
Answer: C) Abscisic acid (ABA)
Explanation: ABA induces stomatal closure during drought stress.
37. The driving force of transpiration pull is:
A) Root pressure
B) Water potential gradient
C) Guttation
D) Osmosis
Answer: B) Water potential gradient
Explanation: Water moves upward along gradient created by evaporation from leaves.
38. The first step of transpiration is:
A) Movement into xylem
B) Evaporation from mesophyll cells into intercellular spaces
C) Diffusion out through stomata
D) Root pressure
Answer: B) Evaporation from mesophyll cells into intercellular spaces
Explanation: Water evaporates from mesophyll into leaf air spaces before diffusing out.
39. The transpiration ratio is:
A) CO₂ fixed / water lost
B) Water lost / CO₂ fixed
C) O₂ released / water lost
D) Water absorbed / water transpired
Answer: B) Water lost / CO₂ fixed
Explanation: It measures efficiency of water use during photosynthesis.
40. Transpiration is measured by:
A) Potometer
B) Hygrometer
C) Psychrometer
D) Porometer
Answer: A) Potometer
Explanation: Potometer (Ganong’s potometer) measures water uptake as an indirect measure of transpiration.
41. The least transpiration occurs in:
A) Xerophytes
B) Hydrophytes
C) Mesophytes
D) Halophytes
Answer: B) Hydrophytes
Explanation: Aquatic plants lose little water due to availability of surrounding water.
42. The phenomenon of guttation occurs mainly at:
A) Stomata
B) Lenticels
C) Hydathodes
D) Cuticle
Answer: C) Hydathodes
Explanation: Specialized pores at leaf margins exude water drops due to root pressure.
43. Which plant will show maximum transpiration rate?
A) Cactus
B) Mango
C) Lotus
D) Water hyacinth
Answer: B) Mango
Explanation: Mesophytes like mango have broad leaves with many stomata, leading to higher transpiration.
44. During midday in summer, the rate of transpiration:
A) Increases continuously
B) Decreases due to stomatal closure
C) Remains constant
D) Stops completely
Answer: B) Decreases due to stomatal closure
Explanation: High temperature + water stress causes stomata to close at midday.
45. Transpiration helps in:
A) Cooling leaves
B) Ascent of sap
C) Distribution of minerals
D) All of these
Answer: D) All of these
Explanation: Transpiration aids in cooling, nutrient movement, and water transport.
46. Antitranspirants reduce transpiration by:
A) Increasing photosynthesis
B) Inducing stomatal closure
C) Increasing root pressure
D) Breaking hydrogen bonds
Answer: B) Inducing stomatal closure
Explanation: Substances like ABA, phenylmercuric acetate reduce transpiration.
47. Water is pulled upward in xylem mainly due to:
A) Root pressure
B) Cohesion and adhesion of water
C) Imbibition
D) Capillarity alone
Answer: B) Cohesion and adhesion of water
Explanation: Cohesion-tension mechanism explains long-distance water transport.
48. Which plant shows Crassulacean Acid Metabolism (CAM) to reduce transpiration?
A) Rice
B) Wheat
C) Opuntia
D) Mango
Answer: C) Opuntia
Explanation: CAM plants open stomata at night to minimize water loss.
49. Xerophytes conserve water by:
A) Thick cuticle
B) Sunken stomata
C) Reduced leaf area
D) All of these
Answer: D) All of these
Explanation: All are adaptations to reduce transpiration in dry habitats.
50. The ascent of sap stops when:
A) Root pressure is low
B) Cohesion of water is lost (air embolism)
C) Temperature is high
D) Cuticle is thick
Answer: B) Cohesion of water is lost (air embolism)
Explanation: Air bubbles in xylem break the water column continuity, stopping sap ascent.
51. The main conducting tissue for mineral nutrients in plants is:
A) Phloem
B) Xylem
C) Cortex
D) Cambium
Answer: B) Xylem
Explanation: Xylem transports water and minerals absorbed from the soil.
52. Essential elements are those which:
A) Are required in large amounts only
B) Cannot be replaced by other elements
C) May or may not be required for metabolism
D) Are required only in hydroponics
Answer: B) Cannot be replaced by other elements
Explanation: An element is considered essential if its absence prevents plant growth and no other element can replace it.
53. Hydroponics is a technique used to:
A) Study root nodules
B) Grow plants without soil
C) Prevent transpiration
D) Increase guttation
Answer: B) Grow plants without soil
Explanation: Hydroponics (solution culture) is used to study mineral requirements of plants.
54. Which mineral is part of chlorophyll?
A) Calcium
B) Magnesium
C) Iron
D) Sulphur
Answer: B) Magnesium
Explanation: Magnesium forms the central atom of chlorophyll molecules.
55. Which mineral is essential for nitrogen fixation in legumes?
A) Boron
B) Iron & Molybdenum
C) Potassium
D) Calcium
Answer: B) Iron & Molybdenum
Explanation: Both are cofactors of nitrogenase enzyme involved in biological nitrogen fixation.
56. Necrosis (death of tissues) is mainly due to deficiency of:
A) K, Ca, Mg
B) Fe, Mn, Zn
C) Mo, B
D) Na, Cl
Answer: A) K, Ca, Mg
Explanation: Deficiency of these minerals leads to death of cells and tissues in leaves.
57. Chlorosis (yellowing of leaves) is caused by deficiency of:
A) N, K, Mg, Fe, S, Mo
B) Ca, B, Mn
C) Na, Cl, Zn
D) P, Cu, Mn
Answer: A) N, K, Mg, Fe, S, Mo
Explanation: These minerals are required for chlorophyll formation; deficiency causes chlorosis.
58. Which mineral is needed for photolysis of water during photosynthesis?
A) Fe
B) Mn
C) Mg
D) Ca
Answer: B) Mn
Explanation: Manganese ions are essential for water-splitting complex in PSII.
59. Which mineral is most immobile in plants?
A) Nitrogen
B) Phosphorus
C) Calcium
D) Potassium
Answer: C) Calcium
Explanation: Calcium is not translocated easily, hence deficiency symptoms appear in young leaves first.
60. Which mineral is required for synthesis of auxin (IAA)?
A) Fe
B) Zn
C) Cu
D) Mg
Answer: B) Zn
Explanation: Zinc is a cofactor for enzymes involved in tryptophan to IAA conversion.
61. The main tissue for transport of organic food in plants is:
A) Xylem
B) Phloem
C) Cambium
D) Endodermis
Answer: B) Phloem
Explanation: Phloem transports sucrose and other organic solutes.
62. Food is transported in phloem mainly in the form of:
A) Glucose
B) Fructose
C) Sucrose
D) Starch
Answer: C) Sucrose
Explanation: Sucrose is the common transport sugar in most plants.
63. In phloem, which cells are responsible for transport?
A) Companion cells & sieve tube elements
B) Tracheids & vessels
C) Phloem parenchyma
D) Cambium cells
Answer: A) Companion cells & sieve tube elements
Explanation: Sieve tubes transport food, and companion cells help in loading/unloading.
64. The direction of food transport in phloem is:
A) Only upward
B) Only downward
C) Both upward and downward
D) Random
Answer: C) Both upward and downward
Explanation: Food is transported bidirectionally depending on source-sink relationship.
65. The pressure-flow hypothesis was proposed by:
A) Dixon & Joly
B) Münch
C) Strasburger
D) Priestley
Answer: B) Münch
Explanation: In 1930, Münch proposed the mass flow or pressure-flow hypothesis for phloem transport.
66. According to pressure-flow hypothesis, transport in phloem occurs due to:
A) Root pressure
B) Turgor pressure gradient
C) ATP energy only
D) Cohesion-tension
Answer: B) Turgor pressure gradient
Explanation: Osmotic pressure builds in source region, creating a pressure difference moving food to sink.
67. In phloem loading, sugars move from mesophyll cells into sieve tubes by:
A) Passive diffusion
B) Active transport
C) Osmosis
D) Capillarity
Answer: B) Active transport
Explanation: Energy (ATP) is required to load sucrose against concentration gradient into sieve tubes.
68. In pressure-flow mechanism, “source” refers to:
A) Organs where food is utilized
B) Organs where food is stored
C) Organs where food is synthesized
D) Root apex
Answer: C) Organs where food is synthesized
Explanation: Source = photosynthetic leaves that produce sugars.
69. In pressure-flow mechanism, “sink” refers to:
A) Leaves
B) Roots, fruits, seeds
C) Xylem
D) Cambium
Answer: B) Roots, fruits, seeds
Explanation: Sink = tissues where sugars are stored or consumed.
70. Phloem transport is:
A) Apoplastic
B) Symplastic
C) Both apoplastic and symplastic
D) Vacuolar only
Answer: C) Both apoplastic and symplastic
Explanation: Sugars move by symplast (plasmodesmata) and apoplast (active loading into phloem).
71. Translocation of food in phloem requires:
A) Light
B) ATP
C) Oxygen
D) Both B and C
Answer: D) Both B and C
Explanation: ATP and aerobic respiration provide energy for phloem loading/unloading.
72. The translocation rate in phloem is:
A) 1 mm/hour
B) 1 m/hour
C) 1 cm/day
D) 0.1 mm/day
Answer: B) 1 m/hour
Explanation: Food moves rapidly in phloem compared to diffusion.
73. The girdling experiment (removal of phloem) shows that:
A) Water transport occurs in phloem
B) Food transport occurs in phloem
C) Minerals move in cortex
D) Transpiration pull occurs in phloem
Answer: B) Food transport occurs in phloem
Explanation: Swelling above girdled area proves food is transported through phloem.
74. The sieve plates in phloem are present in:
A) Sieve tube elements
B) Companion cells
C) Xylem tracheids
D) Phloem parenchyma
Answer: A) Sieve tube elements
Explanation: Sieve plates are perforated walls of sieve tubes facilitating transport.
75. The energy for phloem transport comes from:
A) Photosynthesis directly
B) Active loading by companion cells
C) Transpiration pull
D) Root pressure
Answer: B) Active loading by companion cells
Explanation: Companion cells use ATP to load sugars into sieve tubes, generating pressure flow.
76. The cohesion-tension theory of water transport explains:
A) Phloem transport
B) Ascent of sap in xylem
C) Mineral nutrition
D) Osmosis in root hairs
Answer: B) Ascent of sap in xylem
Explanation: Cohesion-tension theory (Dixon & Joly) explains upward pull of water due to transpiration.
77. Root pressure alone cannot account for water rise in tall trees because:
A) It is too weak
B) It occurs only at night
C) It is absent in dry soil
D) All of these
Answer: D) All of these
Explanation: Root pressure is weak and insufficient to explain ascent of sap beyond a few meters.
78. Which condition favours guttation?
A) Low root pressure, high transpiration
B) High root pressure, low transpiration
C) High transpiration, high temperature
D) None of these
Answer: B) High root pressure, low transpiration
Explanation: Guttation occurs at night/early morning when transpiration is low but root pressure is high.
79. Transpiration pull is strongest in:
A) Midday
B) Midnight
C) Early morning
D) Evening
Answer: A) Midday
Explanation: High temperature and low humidity at midday cause maximum transpiration pull.
80. Which experiment proves that food is translocated through phloem?
A) Plasmolysis experiment
B) Girdling experiment
C) Potometer experiment
D) Bell jar experiment
Answer: B) Girdling experiment
Explanation: Removing a ring of bark (phloem) causes accumulation of food above the girdle.
81. Food translocation in plants is always:
A) From root to shoot
B) From leaves to roots only
C) From source to sink
D) Random
Answer: C) From source to sink
Explanation: Food transport direction depends on where it is produced (source) and where it is needed (sink).
82. The rate of translocation in phloem is approximately:
A) 1 cm/hr
B) 1 m/hr
C) 1 cm/day
D) 1 mm/hr
Answer: B) 1 m/hr
Explanation: Phloem transport is rapid compared to diffusion.
83. Which plant shows CAM photosynthesis to conserve water?
A) Wheat
B) Rice
C) Opuntia
D) Mango
Answer: C) Opuntia
Explanation: CAM plants open stomata at night, reducing water loss.
84. The transpiration-cohesion theory fails if:
A) Water molecules lose cohesion (embolism)
B) Transpiration rate decreases
C) Light intensity is low
D) Root pressure develops
Answer: A) Water molecules lose cohesion (embolism)
Explanation: Air bubbles in xylem break water column, stopping ascent of sap.
85. In hydrophytes, cuticle and transpiration are:
A) Thick and high
B) Absent and negligible
C) Thick and negligible
D) Thin and high
Answer: B) Absent and negligible
Explanation: Aquatic plants don’t need thick cuticle as water loss is not an issue.
86. Xerophytes minimize water loss by:
A) Thick cuticle
B) Sunken stomata
C) Reduced leaves (spines)
D) All of these
Answer: D) All of these
Explanation: These are common xerophytic adaptations.
87. The movement of sugars from mesophyll cells to phloem is called:
A) Phloem loading
B) Phloem unloading
C) Transpiration pull
D) Mineral transport
Answer: A) Phloem loading
Explanation: Sugars are actively loaded into sieve tubes from source cells.
88. Water absorption through mycorrhizal association is most important for:
A) Nitrogen
B) Potassium
C) Phosphorus
D) Calcium
Answer: C) Phosphorus
Explanation: Mycorrhiza greatly enhances phosphorus uptake.
89. Which ion plays a major role in stomatal movement?
A) Na⁺
B) K⁺
C) Ca²⁺
D) Mg²⁺
Answer: B) K⁺
Explanation: Active uptake of K⁺ by guard cells regulates stomatal opening/closure.
90. During drought stress, stomata close due to:
A) Auxin
B) Abscisic acid (ABA)
C) Cytokinin
D) Ethylene
Answer: B) Abscisic acid (ABA)
Explanation: ABA induces stomatal closure to conserve water.
91. In phloem, the living cells that assist sieve tubes are:
A) Phloem fibres
B) Phloem parenchyma
C) Companion cells
D) Cambium cells
Answer: C) Companion cells
Explanation: Companion cells help in loading/unloading of sugars into sieve tubes.
92. In tall trees, ascent of sap occurs mainly due to:
A) Root pressure
B) Transpiration pull
C) Capillarity
D) Osmosis
Answer: B) Transpiration pull
Explanation: Root pressure is insufficient; cohesion-tension mechanism explains water rise.
93. Which plant factor reduces transpiration?
A) Large leaf area
B) Sunken stomata
C) Thin cuticle
D) High stomatal frequency
Answer: B) Sunken stomata
Explanation: Sunken stomata reduce water loss by trapping humid air.
94. In girdling experiment, food accumulates:
A) Below the girdle
B) Above the girdle
C) Both above and below
D) At the root tip
Answer: B) Above the girdle
Explanation: Phloem is removed, so sugars cannot move downward.
95. Which factor reduces the rate of transpiration?
A) High temperature
B) Low humidity
C) High wind velocity
D) High atmospheric humidity
Answer: D) High atmospheric humidity
Explanation: When air is already saturated with water, transpiration rate decreases.
96. The process of guttation is mainly seen in:
A) Tall trees
B) Herbs with large leaves
C) Succulents
D) Xerophytes
Answer: B) Herbs with large leaves
Explanation: Guttation occurs through hydathodes, commonly in plants like tomato, colocasia, grasses.
97. Active transport in phloem requires:
A) ATP
B) Osmosis
C) Root pressure
D) Cohesion
Answer: A) ATP
Explanation: Loading and unloading of sugars in phloem requires metabolic energy.
98. The closing of stomata at night is mainly due to:
A) CO₂ accumulation
B) Loss of turgor in guard cells
C) High transpiration rate
D) ABA action
Answer: B) Loss of turgor in guard cells
Explanation: Guard cells lose water at night → stomata close.
99. Which statement is correct regarding translocation of food?
A) It occurs only in downward direction
B) It occurs only during the day
C) It occurs both upward and downward
D) It is independent of source and sink
Answer: C) It occurs both upward and downward
Explanation: Phloem translocation is bidirectional (source to sink).
100. Which is the most accepted theory of food transport in plants?
A) Diffusion theory
B) Protoplasmic streaming theory
C) Pressure-flow hypothesis
D) Electro-osmotic theory
Answer: C) Pressure-flow hypothesis
Explanation: Münch’s pressure-flow (mass flow) hypothesis is widely accepted for phloem translocation.