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Plant Physiology & Biochemical Pathways (Botany & Plant Sciences) Solved Questions & Notes (2026) - Apex Rankers

Natural & Physical Sciences > Botany & Plant Sciences > Plant Physiology & Biochemical Pathways

100 Total Questions
~150 mins Read Time
1 Subject Areas
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Q. 1 MULTIPLE_CHOICE
Difficulty: EASY (1 Mark)
The primary carbon-fixing enzyme in C3 photosynthetic Calvin cycle is:
A
ATP synthase
B
PEP carboxylase
C
Amylase
D
RuBisCO (Ribulose-1,5-bisphosphate carboxylase-oxygenase)
✓ Correct
💡 Step-by-Step Explanation & Concept Rationale
RuBisCO fixes atmospheric CO2 onto RuBP to yield two molecules of 3-PGA.
Q. 2 MULTIPLE_CHOICE
Difficulty: MEDIUM (1 Mark)
In C4 plants (e.g. Maize, Sugarcane), initial CO2 fixation occurs in mesophyll cells catalyzed by:
A
Hexokinase
B
RuBisCO
C
PEP Carboxylase (yielding Oxaloacetate)
✓ Correct
D
Carbonic anhydrase
💡 Step-by-Step Explanation & Concept Rationale
PEP carboxylase lacks oxygenase activity, preventing wasteful photorespiration.
Q. 3 MULTIPLE_CHOICE
Difficulty: EASY (1 Mark)
Which plant hormone is primarily responsible for apical dominance and phototropism?
A
Cytokinin
B
Auxin (Indole-3-acetic acid, IAA)
✓ Correct
C
Gibberellin
D
Abscisic acid
💡 Step-by-Step Explanation & Concept Rationale
Polar basipetal auxin transport from the apical shoot tip inhibits axillary lateral buds.
Q. 4 MULTIPLE_CHOICE
Difficulty: EASY (1 Mark)
The stress hormone responsible for stomatal closure during drought is:
A
Ethylene
B
Auxin
C
Gibberellin
D
Abscisic Acid (ABA)
✓ Correct
💡 Step-by-Step Explanation & Concept Rationale
ABA triggers rapid efflux of potassium and anions from guard cells, causing loss of turgor.
Q. 5 MULTIPLE_CHOICE
Difficulty: MEDIUM (1 Mark)
Water moves upward in tall trees primarily driven by the mechanism of:
A
Transpiration Pull and Cohesion-Tension Theory
✓ Correct
B
Active root pumping
C
Capillarity alone
D
Atmospheric pressure only
💡 Step-by-Step Explanation & Concept Rationale
Dixon and Joly's cohesion theory explains continuous water column pull under negative tension.
Q. 6 MULTIPLE_CHOICE
Difficulty: EASY (1 Mark)
In professional practice: The primary carbon-fixing enzyme in C3 photosynthetic Calvin cycle is:
A
RuBisCO (Ribulose-1,5-bisphosphate carboxylase-oxygenase)
✓ Correct
B
Amylase
C
ATP synthase
D
PEP carboxylase
💡 Step-by-Step Explanation & Concept Rationale
RuBisCO fixes atmospheric CO2 onto RuBP to yield two molecules of 3-PGA.
Q. 7 MULTIPLE_CHOICE
Difficulty: MEDIUM (1 Mark)
In professional practice: In C4 plants (e.g. Maize, Sugarcane), initial CO2 fixation occurs in mesophyll cells catalyzed by:
A
Hexokinase
B
Carbonic anhydrase
C
RuBisCO
D
PEP Carboxylase (yielding Oxaloacetate)
✓ Correct
💡 Step-by-Step Explanation & Concept Rationale
PEP carboxylase lacks oxygenase activity, preventing wasteful photorespiration.
Q. 8 MULTIPLE_CHOICE
Difficulty: EASY (1 Mark)
In professional practice: Which plant hormone is primarily responsible for apical dominance and phototropism?
A
Gibberellin
B
Cytokinin
C
Abscisic acid
D
Auxin (Indole-3-acetic acid, IAA)
✓ Correct
💡 Step-by-Step Explanation & Concept Rationale
Polar basipetal auxin transport from the apical shoot tip inhibits axillary lateral buds.
Q. 9 MULTIPLE_CHOICE
Difficulty: EASY (1 Mark)
In professional practice: The stress hormone responsible for stomatal closure during drought is:
A
Abscisic Acid (ABA)
✓ Correct
B
Gibberellin
C
Ethylene
D
Auxin
💡 Step-by-Step Explanation & Concept Rationale
ABA triggers rapid efflux of potassium and anions from guard cells, causing loss of turgor.
Q. 10 MULTIPLE_CHOICE
Difficulty: MEDIUM (1 Mark)
In professional practice: Water moves upward in tall trees primarily driven by the mechanism of:
A
Active root pumping
B
Transpiration Pull and Cohesion-Tension Theory
✓ Correct
C
Capillarity alone
D
Atmospheric pressure only
💡 Step-by-Step Explanation & Concept Rationale
Dixon and Joly's cohesion theory explains continuous water column pull under negative tension.
Q. 11 MULTIPLE_CHOICE
Difficulty: EASY (1 Mark)
According to standard examination standards: The primary carbon-fixing enzyme in C3 photosynthetic Calvin cycle is:
A
Amylase
B
ATP synthase
C
RuBisCO (Ribulose-1,5-bisphosphate carboxylase-oxygenase)
✓ Correct
D
PEP carboxylase
💡 Step-by-Step Explanation & Concept Rationale
RuBisCO fixes atmospheric CO2 onto RuBP to yield two molecules of 3-PGA.
Q. 12 MULTIPLE_CHOICE
Difficulty: MEDIUM (1 Mark)
According to standard examination standards: In C4 plants (e.g. Maize, Sugarcane), initial CO2 fixation occurs in mesophyll cells catalyzed by:
A
Hexokinase
B
Carbonic anhydrase
C
PEP Carboxylase (yielding Oxaloacetate)
✓ Correct
D
RuBisCO
💡 Step-by-Step Explanation & Concept Rationale
PEP carboxylase lacks oxygenase activity, preventing wasteful photorespiration.
Q. 13 MULTIPLE_CHOICE
Difficulty: EASY (1 Mark)
According to standard examination standards: Which plant hormone is primarily responsible for apical dominance and phototropism?
A
Gibberellin
B
Auxin (Indole-3-acetic acid, IAA)
✓ Correct
C
Abscisic acid
D
Cytokinin
💡 Step-by-Step Explanation & Concept Rationale
Polar basipetal auxin transport from the apical shoot tip inhibits axillary lateral buds.
Q. 14 MULTIPLE_CHOICE
Difficulty: EASY (1 Mark)
According to standard examination standards: The stress hormone responsible for stomatal closure during drought is:
A
Auxin
B
Abscisic Acid (ABA)
✓ Correct
C
Ethylene
D
Gibberellin
💡 Step-by-Step Explanation & Concept Rationale
ABA triggers rapid efflux of potassium and anions from guard cells, causing loss of turgor.
Q. 15 MULTIPLE_CHOICE
Difficulty: MEDIUM (1 Mark)
According to standard examination standards: Water moves upward in tall trees primarily driven by the mechanism of:
A
Atmospheric pressure only
B
Capillarity alone
C
Transpiration Pull and Cohesion-Tension Theory
✓ Correct
D
Active root pumping
💡 Step-by-Step Explanation & Concept Rationale
Dixon and Joly's cohesion theory explains continuous water column pull under negative tension.
Q. 16 MULTIPLE_CHOICE
Difficulty: EASY (1 Mark)
From an applied perspective: The primary carbon-fixing enzyme in C3 photosynthetic Calvin cycle is:
A
Amylase
B
PEP carboxylase
C
RuBisCO (Ribulose-1,5-bisphosphate carboxylase-oxygenase)
✓ Correct
D
ATP synthase
💡 Step-by-Step Explanation & Concept Rationale
RuBisCO fixes atmospheric CO2 onto RuBP to yield two molecules of 3-PGA.
Q. 17 MULTIPLE_CHOICE
Difficulty: MEDIUM (1 Mark)
From an applied perspective: In C4 plants (e.g. Maize, Sugarcane), initial CO2 fixation occurs in mesophyll cells catalyzed by:
A
RuBisCO
B
Carbonic anhydrase
C
PEP Carboxylase (yielding Oxaloacetate)
✓ Correct
D
Hexokinase
💡 Step-by-Step Explanation & Concept Rationale
PEP carboxylase lacks oxygenase activity, preventing wasteful photorespiration.
Q. 18 MULTIPLE_CHOICE
Difficulty: EASY (1 Mark)
From an applied perspective: Which plant hormone is primarily responsible for apical dominance and phototropism?
A
Auxin (Indole-3-acetic acid, IAA)
✓ Correct
B
Cytokinin
C
Gibberellin
D
Abscisic acid
💡 Step-by-Step Explanation & Concept Rationale
Polar basipetal auxin transport from the apical shoot tip inhibits axillary lateral buds.
Q. 19 MULTIPLE_CHOICE
Difficulty: EASY (1 Mark)
From an applied perspective: The stress hormone responsible for stomatal closure during drought is:
A
Auxin
B
Gibberellin
C
Abscisic Acid (ABA)
✓ Correct
D
Ethylene
💡 Step-by-Step Explanation & Concept Rationale
ABA triggers rapid efflux of potassium and anions from guard cells, causing loss of turgor.
Q. 20 MULTIPLE_CHOICE
Difficulty: MEDIUM (1 Mark)
From an applied perspective: Water moves upward in tall trees primarily driven by the mechanism of:
A
Active root pumping
B
Atmospheric pressure only
C
Capillarity alone
D
Transpiration Pull and Cohesion-Tension Theory
✓ Correct
💡 Step-by-Step Explanation & Concept Rationale
Dixon and Joly's cohesion theory explains continuous water column pull under negative tension.
Q. 21 MULTIPLE_CHOICE
Difficulty: EASY (1 Mark)
Under standard operational protocols: The primary carbon-fixing enzyme in C3 photosynthetic Calvin cycle is:
A
PEP carboxylase
B
Amylase
C
RuBisCO (Ribulose-1,5-bisphosphate carboxylase-oxygenase)
✓ Correct
D
ATP synthase
💡 Step-by-Step Explanation & Concept Rationale
RuBisCO fixes atmospheric CO2 onto RuBP to yield two molecules of 3-PGA.
Q. 22 MULTIPLE_CHOICE
Difficulty: MEDIUM (1 Mark)
Under standard operational protocols: In C4 plants (e.g. Maize, Sugarcane), initial CO2 fixation occurs in mesophyll cells catalyzed by:
A
Hexokinase
B
Carbonic anhydrase
C
RuBisCO
D
PEP Carboxylase (yielding Oxaloacetate)
✓ Correct
💡 Step-by-Step Explanation & Concept Rationale
PEP carboxylase lacks oxygenase activity, preventing wasteful photorespiration.
Q. 23 MULTIPLE_CHOICE
Difficulty: EASY (1 Mark)
Under standard operational protocols: Which plant hormone is primarily responsible for apical dominance and phototropism?
A
Auxin (Indole-3-acetic acid, IAA)
✓ Correct
B
Gibberellin
C
Abscisic acid
D
Cytokinin
💡 Step-by-Step Explanation & Concept Rationale
Polar basipetal auxin transport from the apical shoot tip inhibits axillary lateral buds.
Q. 24 MULTIPLE_CHOICE
Difficulty: EASY (1 Mark)
Under standard operational protocols: The stress hormone responsible for stomatal closure during drought is:
A
Gibberellin
B
Ethylene
C
Auxin
D
Abscisic Acid (ABA)
✓ Correct
💡 Step-by-Step Explanation & Concept Rationale
ABA triggers rapid efflux of potassium and anions from guard cells, causing loss of turgor.
Q. 25 MULTIPLE_CHOICE
Difficulty: MEDIUM (1 Mark)
Under standard operational protocols: Water moves upward in tall trees primarily driven by the mechanism of:
A
Transpiration Pull and Cohesion-Tension Theory
✓ Correct
B
Active root pumping
C
Capillarity alone
D
Atmospheric pressure only
💡 Step-by-Step Explanation & Concept Rationale
Dixon and Joly's cohesion theory explains continuous water column pull under negative tension.
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