Home Subjects NEET Botany Plant Physiology

NEET Botany
Plant Physiology

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

26 Q 7 Topics Take Mock Test
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Difficulty: All Easy Medium Hard 11–20 of 26
Topics in NEET Botany
In the Calvin cycle, which enzyme catalyzes the fixation of CO2?
A Ribulose-1,5-bisphosphate carboxylase (RuBisCO)
B Phosphofructokinase
C Aldolase
D Transketolase
Correct Answer:  A. Ribulose-1,5-bisphosphate carboxylase (RuBisCO)
EXPLANATION

RuBisCO is the most abundant enzyme on Earth and catalyzes the carboxylation of RuBP with CO2 in the dark reactions.

Test
During photosynthesis, the splitting of water molecules occurs in which compartment of the chloroplast?
A Stroma
B Thylakoid lumen
C Outer membrane
D Inner membrane
Correct Answer:  B. Thylakoid lumen
EXPLANATION

Water photolysis (photosystem II) occurs in the thylakoid lumen where oxygen is released as a byproduct.

Test
A student observes that a plant kept in a completely dark room still shows some gas exchange. This can be attributed to:
A Photorespiration
B Aerobic respiration
C Fermentation
D Chemosynthesis
Correct Answer:  B. Aerobic respiration
EXPLANATION

In darkness, photosynthesis stops, but aerobic respiration continues, consuming O2 and releasing CO2, resulting in measurable gas exchange.

Test
Which hormone is primarily responsible for closing stomata under water stress conditions?
A Gibberellin
B Abscisic acid (ABA)
C Auxin
D Cytokinin
Correct Answer:  B. Abscisic acid (ABA)
EXPLANATION

ABA accumulates in guard cells during water stress and causes stomatal closure by reducing turgor pressure in guard cells.

Test
In C4 photosynthesis, the primary CO2 acceptor molecule is:
A Oxaloacetate
B Phosphoenolpyruvate (PEP)
C 3-Phosphoglycerate
D Ribulose-1,5-bisphosphate
Correct Answer:  B. Phosphoenolpyruvate (PEP)
EXPLANATION

In C4 plants, CO2 first combines with PEP (3-carbon molecule) to form oxaloacetate (4-carbon), which is why it's called C4 photosynthesis.

Test
The rate of transpiration is LEAST affected by which of the following factors?
A Light intensity
B Soil pH
C Relative humidity
D Temperature
Correct Answer:  B. Soil pH
EXPLANATION

Soil pH has minimal direct effect on transpiration rate. Primary factors affecting transpiration are light, humidity, temperature, and wind velocity.

Test
Which of the following is the primary pigment involved in capturing light energy during photosynthesis?
A Chlorophyll a
B Chlorophyll b
C Xanthophyll
D Carotenoid
Correct Answer:  A. Chlorophyll a
EXPLANATION

Chlorophyll a is the primary pigment that directly participates in the photochemical reactions of both PSI and PSII, while other pigments act as accessory pigments.

Test
In phloem transport, the source is typically the:
A Root tip
B Leaf lamina (photosynthetically active tissue)
C Stem apex
D Flower buds
Correct Answer:  B. Leaf lamina (photosynthetically active tissue)
EXPLANATION

The source in phloem transport is any photosynthetically active tissue, primarily mature leaves, which produce and load photosynthates into sieve tubes.

Test
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.

Test
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.

Test
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