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NEET Botany

Botany questions for NEET UG — Plant Anatomy, Physiology, Reproduction, Ecology.

276 Q 3 Topics Take Test
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Difficulty: All Easy Medium Hard 51–60 of 276
Topics in NEET Botany
All Plant Kingdom 100 Plant Anatomy 100 Plant Physiology 76
The process of photorespiration in C3 plants is initiated when:
A CO2 concentration is very high
B O2 concentration is very low
C O2 concentration is very high and CO2 is low
D Temperature is below 10°C
Correct Answer:  C. O2 concentration is very high and CO2 is low
EXPLANATION

Photorespiration occurs when RuBisCO catalyzes oxygenation of RuBP instead of carboxylation, which happens under high O2 and low CO2 conditions.

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Which of the following hormones primarily promotes stomatal closure in response to water stress?
A Auxin
B Abscisic acid (ABA)
C Gibberellin
D Cytokinin
Correct Answer:  B. Abscisic acid (ABA)
EXPLANATION

Abscisic acid is the stress hormone that promotes stomatal closure during drought by reducing guard cell turgor pressure, thereby reducing water loss.

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Q.53 Medium Plant Physiology
During active transport, which of the following statements is NOT correct?
A It requires ATP hydrolysis
B It moves substances against concentration gradient
C It involves carrier proteins
D It is independent of metabolic activities
Correct Answer:  D. It is independent of metabolic activities
EXPLANATION

Active transport is entirely dependent on metabolic activities and ATP availability. It requires energy to move substances against their concentration gradient.

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Which element is essential for the synthesis of chlorophyll and is present at the center of the chlorophyll molecule?
A Iron
B Magnesium
C Manganese
D Copper
Correct Answer:  B. Magnesium
EXPLANATION

Magnesium is the central atom in the porphyrin ring of chlorophyll molecules, making it essential for photosynthetic light absorption.

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Q.55 Medium Plant Physiology
The phenomenon where plants exhibit different photosynthetic rates at different light intensities until a plateau is reached is called:
A Light saturation point
B Photorespiration threshold
C Compensation point
D Quantum yield
Correct Answer:  A. Light saturation point
EXPLANATION

The light saturation point is the light intensity beyond which photosynthesis does not increase, indicating maximum rate of photosynthesis has been achieved.

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Q.56 Medium Plant Physiology
Which of the following stomatal movements is primarily controlled by turgor pressure changes in guard cells?
A Nyctinastic movements
B Photonastic movements
C Hydroactive movements
D Thermonastic movements
Correct Answer:  C. Hydroactive movements
EXPLANATION

Stomatal opening and closing are mainly controlled by hydroactive movements, which involve osmotic changes in guard cells due to potassium ion accumulation.

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During photosynthesis, the light-independent reactions occur in which compartment of the chloroplast?
A Stroma
B Thylakoid membrane
C Inner membrane
D Outer membrane
Correct Answer:  A. Stroma
EXPLANATION

The Calvin cycle (light-independent reactions) takes place in the stroma of chloroplasts, where CO2 is fixed and glucose is synthesized.

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Which enzyme catalyzes the fixation of CO2 in the Calvin cycle?
A Phosphoenolpyruvate carboxylase
B RuBisCO (Ribulose-1,5-bisphosphate carboxylase)
C Aldolase
D Enolase
Correct Answer:  B. RuBisCO (Ribulose-1,5-bisphosphate carboxylase)
EXPLANATION

RuBisCO catalyzes the carboxylation of RuBP with CO2 to form 3-phosphoglycerate, the first stable product of dark reactions in C3 plants.

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The ratio of photosynthesis to respiration in a plant is represented by:
A Compensation point
B Net assimilation rate
C Gross assimilation rate
D Apparent photosynthesis
Correct Answer:  D. Apparent photosynthesis
EXPLANATION

Apparent photosynthesis (net photosynthesis) represents the actual photosynthesis minus respiration measured as the gaseous exchange in the plant.

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Which of the following is a characteristic of phloem transport?
A It is a passive process
B It moves only upwards
C It is bidirectional
D It requires no energy
Correct Answer:  C. It is bidirectional
EXPLANATION

Phloem transport is bidirectional and can move sugars upwards or downwards depending on source-sink relationships and requires metabolic energy.

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