Practice 100 Plant Physiology MCQs with answers covering photosynthesis, respiration, transpiration, mineral nutrition, plant hormones, and water transport—ideal for students and exams.
Plant Physiology is a core branch of biology that explores how plants function, grow, and respond to their environment. Understanding key processes such as photosynthesis, respiration, transpiration, mineral nutrition, water transport, and the role of plant hormones is essential for students and competitive exam aspirants. This article presents 100 carefully prepared Plant Physiology MCQs with answers, designed to strengthen conceptual understanding, support quick revision, and improve exam performance. These plant physiology multiple choice questions are ideal for school exams, entrance tests, and general biology practice.
Sure! Below are 100 Multiple Choice Questions (MCQs) on Plant Physiology, written in clear and correct English, suitable for exams, practice, and revision.
🌿 Plant Physiology – 100 MCQs with Answers
1. Plant Physiology is the study of:
A. Plant structure
B. Plant classification
C. Plant functions and processes
D. Plant evolution
Answer: C
2. The process by which plants make food is called:
A. Respiration
B. Transpiration
C. Photosynthesis
D. Germination
Answer: C
3. Chlorophyll is found in:
A. Mitochondria
B. Ribosomes
C. Chloroplasts
D. Vacuoles
Answer: C
4. The main pigment involved in photosynthesis is:
A. Carotene
B. Xanthophyll
C. Chlorophyll-a
D. Anthocyanin
Answer: C
5. Photosynthesis occurs mainly in:
A. Roots
B. Stem
C. Flowers
D. Leaves
Answer: D
6. The light reaction of photosynthesis occurs in:
A. Stroma
B. Thylakoid membrane
C. Cytoplasm
D. Nucleus
Answer: B
7. The dark reaction of photosynthesis is also known as:
A. Krebs cycle
B. Calvin cycle
C. Glycolysis
D. Electron transport chain
Answer: B
8. Which gas is released during photosynthesis?
A. Carbon dioxide
B. Nitrogen
C. Oxygen
D. Hydrogen
Answer: C
9. The opening and closing of stomata is controlled by:
A. Root hairs
B. Guard cells
C. Epidermal cells
D. Mesophyll cells
Answer: B
10. Transpiration mainly occurs through:
A. Lenticels
B. Cuticle
C. Stomata
D. Roots
Answer: C
11. Which factor does NOT affect transpiration?
A. Temperature
B. Light
C. Wind
D. Soil pH
Answer: D
12. Water absorption in plants mainly occurs through:
A. Leaves
B. Stem
C. Root hairs
D. Flowers
Answer: C
13. The upward movement of water in plants is called:
A. Diffusion
B. Osmosis
C. Translocation
D. Ascent of sap
Answer: D
14. Xylem transports:
A. Food
B. Water and minerals
C. Hormones
D. Gases
Answer: B
15. Phloem transports:
A. Water
B. Minerals
C. Food
D. Oxygen
Answer: C
16. The movement of food in plants is called:
A. Diffusion
B. Transpiration
C. Translocation
D. Osmosis
Answer: C
17. The pressure flow hypothesis explains:
A. Water absorption
B. Transpiration
C. Food translocation
D. Photosynthesis
Answer: C
18. Respiration in plants occurs in:
A. Chloroplast
B. Mitochondria
C. Ribosome
D. Vacuole
Answer: B
19. Which gas is required for respiration?
A. Carbon dioxide
B. Nitrogen
C. Oxygen
D. Hydrogen
Answer: C
20. The end product of aerobic respiration is:
A. Glucose
B. Oxygen
C. Carbon dioxide and water
D. Lactic acid
Answer: C
21. Anaerobic respiration in plants produces:
A. Alcohol and CO₂
B. Lactic acid
C. Water
D. Oxygen
Answer: A
22. Plant hormones are also known as:
A. Vitamins
B. Enzymes
C. Phytohormones
D. Minerals
Answer: C
23. Which hormone promotes cell elongation?
A. Cytokinin
B. Auxin
C. Ethylene
D. Abscisic acid
Answer: B
24. Gibberellins promote:
A. Leaf fall
B. Fruit ripening
C. Stem elongation
D. Dormancy
Answer: C
25. Cytokinins are mainly involved in:
A. Root growth
B. Cell division
C. Leaf abscission
D. Senescence
Answer: B
26. Ethylene is responsible for:
A. Seed germination
B. Fruit ripening
C. Cell elongation
D. Root growth
Answer: B
27. Abscisic acid promotes:
A. Growth
B. Dormancy
C. Cell division
D. Fruit ripening
Answer: B
28. Which hormone inhibits plant growth?
A. Auxin
B. Gibberellin
C. Cytokinin
D. Abscisic acid
Answer: D
29. Mineral nutrition in plants refers to:
A. Photosynthesis
B. Water absorption
C. Uptake of minerals
D. Respiration
Answer: C
30. Which element is a macronutrient?
A. Iron
B. Zinc
C. Nitrogen
D. Copper
Answer: C
31. Which element is a micronutrient?
A. Potassium
B. Calcium
C. Magnesium
D. Iron
Answer: D
32. Nitrogen deficiency causes:
A. Yellowing of leaves
B. Root decay
C. Excess growth
D. Thick stems
Answer: A
33. Potassium helps in:
A. Protein synthesis
B. Stomatal movement
C. Cell division
D. Seed dormancy
Answer: B
34. Calcium is important for:
A. Chlorophyll formation
B. Cell wall formation
C. Enzyme activity
D. Transpiration
Answer: B
35. Magnesium is a component of:
A. Cell wall
B. ATP
C. Chlorophyll
D. DNA
Answer: C
36. Iron is required for:
A. Chlorophyll synthesis
B. Respiration
C. Photosynthesis
D. Protein digestion
Answer: A
37. Which process involves movement of molecules from high to low concentration?
A. Osmosis
B. Diffusion
C. Active transport
D. Translocation
Answer: B
38. Osmosis requires:
A. Energy
B. Living cells
C. Semi-permeable membrane
D. Pressure
Answer: C
39. Active transport requires:
A. No energy
B. Energy
C. Passive movement
D. High concentration
Answer: B
40. Root pressure helps in:
A. Food transport
B. Transpiration
C. Water movement
D. Photosynthesis
Answer: C
41. Transpiration pull is created due to:
A. Root pressure
B. Cohesion of water
C. Evaporation of water
D. Osmosis
Answer: C
42. Cohesion refers to attraction between:
A. Water and walls
B. Water molecules
C. Roots and soil
D. Leaves and air
Answer: B
43. Adhesion refers to attraction between:
A. Water molecules
B. Water and vessel walls
C. Roots and leaves
D. Cells and tissues
Answer: B
44. The main carbohydrate formed in photosynthesis is:
A. Sucrose
B. Starch
C. Cellulose
D. Glucose
Answer: D
45. Starch is stored in:
A. Roots and stems
B. Leaves only
C. Seeds only
D. Flowers
Answer: A
46. Opening of stomata occurs due to:
A. Loss of water
B. Increase in turgidity
C. Cell death
D. Root pressure
Answer: B
47. Closing of stomata occurs due to:
A. Increased turgor
B. Loss of turgor
C. Cell division
D. Respiration
Answer: B
48. Photorespiration occurs in:
A. Chloroplast only
B. Mitochondria only
C. Chloroplast and mitochondria
D. Cytoplasm
Answer: C
49. C4 plants differ from C3 plants because they:
A. Lack chlorophyll
B. Have Kranz anatomy
C. Do not photosynthesize
D. Lack stomata
Answer: B
50. CAM plants open stomata during:
A. Day
B. Night
C. Morning
D. Evening
Answer: B
51. Transpiration helps in:
A. Cooling of plant
B. Food synthesis
C. Cell division
D. Germination
Answer: A
52. The unit of transpiration rate is:
A. ml/day
B. g/m²/hour
C. cm/sec
D. mol/sec
Answer: B
53. Which tissue conducts water?
A. Phloem
B. Cambium
C. Xylem
D. Cortex
Answer: C
54. Which tissue conducts food?
A. Xylem
B. Phloem
C. Cambium
D. Pith
Answer: B
55. The energy currency of the cell is:
A. DNA
B. RNA
C. ATP
D. ADP
Answer: C
56. Glycolysis occurs in:
A. Mitochondria
B. Cytoplasm
C. Chloroplast
D. Nucleus
Answer: B
57. Krebs cycle occurs in:
A. Cytoplasm
B. Chloroplast
C. Mitochondria
D. Nucleus
Answer: C
58. The respiratory quotient (RQ) is:
A. O₂ consumed / CO₂ released
B. CO₂ released / O₂ consumed
C. ATP produced
D. Energy released
Answer: B
59. RQ of carbohydrates is:
A. 0.7
B. 1
C. 0.9
D. 2
Answer: B
60. RQ of fats is:
A. 1
B. 0.7
C. 2
D. 0.9
Answer: B
61. Which plant hormone delays senescence?
A. Auxin
B. Ethylene
C. Cytokinin
D. ABA
Answer: C
62. Vernalization is related to:
A. Flowering
B. Seed germination
C. Fruit ripening
D. Photosynthesis
Answer: A
63. Photoperiodism is the response to:
A. Temperature
B. Light duration
C. Water
D. Soil nutrients
Answer: B
64. Long-day plants flower when:
A. Nights are long
B. Days are short
C. Days are long
D. Temperature is high
Answer: C
65. Short-day plants flower when:
A. Days are long
B. Nights are long
C. Light is continuous
D. Temperature is low
Answer: B
66. Florigen is associated with:
A. Leaf growth
B. Root growth
C. Flowering
D. Senescence
Answer: C
67. Which element is essential for protein synthesis?
A. Potassium
B. Nitrogen
C. Calcium
D. Iron
Answer: B
68. Boron deficiency affects:
A. Photosynthesis
B. Cell wall formation
C. Root growth
D. Flowering
Answer: B
69. The main function of leaves is:
A. Support
B. Storage
C. Photosynthesis
D. Absorption
Answer: C
70. The site of gaseous exchange in plants is:
A. Roots
B. Stem
C. Leaves
D. Flowers
Answer: C
71. The main source of oxygen in photosynthesis is:
A. CO₂
B. Water
C. Glucose
D. Air
Answer: B
72. Which factor affects the rate of photosynthesis?
A. Light intensity
B. CO₂ concentration
C. Temperature
D. All of these
Answer: D
73. Law of limiting factors was proposed by:
A. Darwin
B. Blackman
C. Mendel
D. Priestley
Answer: B
74. Which scientist discovered photosynthesis?
A. Darwin
B. Priestley
C. Mendel
D. Watson
Answer: B
75. The end product of photosynthesis stored in plants is:
A. Glucose
B. Starch
C. Sucrose
D. Cellulose
Answer: B
76. Which pigment absorbs blue light?
A. Chlorophyll-a
B. Chlorophyll-b
C. Carotene
D. All of these
Answer: D
77. Which plant movement is growth-based?
A. Nastic
B. Turgor movement
C. Tropic movement
D. Sleep movement
Answer: C
78. Phototropism is movement in response to:
A. Gravity
B. Water
C. Light
D. Touch
Answer: C
79. Geotropism is movement in response to:
A. Light
B. Gravity
C. Water
D. Heat
Answer: B
80. Hydrotropism is movement in response to:
A. Light
B. Water
C. Gravity
D. Temperature
Answer: B
81. Thigmotropism is movement in response to:
A. Light
B. Touch
C. Water
D. Gravity
Answer: B
82. The opening of flowers in morning is an example of:
A. Tropic movement
B. Nastic movement
C. Growth movement
D. Turgor movement
Answer: B
83. The loss of water from aerial parts is:
A. Respiration
B. Transpiration
C. Absorption
D. Translocation
Answer: B
84. Cuticular transpiration occurs through:
A. Stomata
B. Lenticels
C. Cuticle
D. Roots
Answer: C
85. Lenticular transpiration occurs in:
A. Leaves
B. Roots
C. Woody stems
D. Flowers
Answer: C
86. The main force for water ascent is:
A. Root pressure
B. Capillarity
C. Transpiration pull
D. Osmosis
Answer: C
87. Water potential is denoted by:
A. Ψw
B. Ψs
C. Ψp
D. Ψg
Answer: A
88. Solute potential is always:
A. Positive
B. Zero
C. Negative
D. Neutral
Answer: C
89. Pressure potential is usually:
A. Negative
B. Positive
C. Zero
D. Neutral
Answer: B
90. The movement of ions against gradient is:
A. Diffusion
B. Osmosis
C. Active transport
D. Passive transport
Answer: C
91. Which mineral activates enzymes?
A. Potassium
B. Nitrogen
C. Phosphorus
D. Calcium
Answer: A
92. Phosphorus is important for:
A. ATP formation
B. Cell wall
C. Chlorophyll
D. Enzyme inhibition
Answer: A
93. Sulfur is a component of:
A. Carbohydrates
B. Proteins
C. Lipids
D. Vitamins
Answer: B
94. Which nutrient deficiency causes poor flowering?
A. Nitrogen
B. Phosphorus
C. Potassium
D. Iron
Answer: B
95. Chlorosis refers to:
A. Leaf fall
B. Yellowing of leaves
C. Root decay
D. Cell death
Answer: B
96. Necrosis refers to:
A. Leaf yellowing
B. Cell death
C. Cell elongation
D. Growth promotion
Answer: B
97. The first stable product of C3 cycle is:
A. PEP
B. RuBP
C. PGA
D. OAA
Answer: C
98. The first stable product of C4 cycle is:
A. PGA
B. RuBP
C. OAA
D. Glucose
Answer: C
99. RuBisCO enzyme is involved in:
A. Respiration
B. Transpiration
C. Carbon fixation
D. Translocation
Answer: C
100. Plant physiology helps us understand:
A. Plant classification
B. Plant evolution
C. Plant life processes
D. Plant fossils
Answer: C
