Which of the following is the primary source of energy for all ecosystems?

The correct answer is A: Solar radiation. Solar radiation is the ultimate source of energy for all ecosystems. Plants capture this energy through photosynthesis, which forms the base of all food chains.

Rhizoids in bryophytes serve primarily for:

The correct answer is B: Anchorage and water absorption. Rhizoids are root-like structures that anchor bryophytes to the substrate and facilitate absorption of water and minerals.

Bt cotton is transgenic cotton resistant to which pest?

The correct answer is B: Bollworm. Bt cotton produces Cry1Ac protein from Bacillus thuringiensis that provides resistance against the cotton bollworm (Helicoverpa armigera).

In the electron transport chain of photosynthesis, the role of cytochrome b6f complex is to:

The correct answer is B: Pump protons into thylakoid lumen and transfer electrons. The cytochrome b6f complex transfers electrons between PSII and PSI while simultaneously pumping H+ ions into thylakoid lumen for chemiosmosis.

The concept of 'ecological niche' refers to:

The correct answer is B: The specific role and position of an organism in its environment, including its habitat and function. An ecological niche encompasses the organism's habitat, food, behavior, and role in the ecosystem - essentially its complete functional position in the environment.

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NEET Botany

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

90 Q 7 Topics Take Mock Test

Difficulty: All Easy Medium Hard 21–30 of 90

Topics in NEET Botany

All Plant Kingdom 100 Plant Anatomy 100 Plant Physiology 100 Reproduction in Plants 60 Genetics & Heredity 20 Ecology & Environment 20 Biotechnology in Plants 20

Q.21 Hard Reproduction in Plants

Which of the following statements about pollen grains is INCORRECT?

A Each pollen grain contains two cells initially

B Pollen wall consists of exine and intine

C Pollen grains are always unicellular

D Generative cell undergoes mitosis to form sperm cells

Correct Answer: C. Pollen grains are always unicellular

EXPLANATION

Mature pollen grains are bicellular (or sometimes tricellular), not unicellular. They contain vegetative and generative cells.

Test

Q.22 Hard Plant Physiology

A research study on stomatal regulation shows that ABA (abscisic acid) concentration increases 100-fold in guard cells during drought stress. Which of the following correctly describes the mechanism?

A ABA activates K+ channels, causing K+ influx and stomatal opening

B ABA increases cAMP levels, triggering anion channel opening and guard cell depolarization

C ABA activates phospholipase C, generating IP3 and causing Ca2+ release, leading to anion efflux and stomatal closure

D ABA directly inhibits photosystem II, preventing photophosphorylation in guard cells

Correct Answer: C. ABA activates phospholipase C, generating IP3 and causing Ca2+ release, leading to anion efflux and stomatal closure

EXPLANATION

ABA stress signaling involves activation of phospholipase C → IP3 generation → Ca2+ release from vacuoles → opening of anion channels (Cl-, malate) → efflux of anions and K+ → loss of turgor → stomatal closure. This is the canonical ABA-signaling pathway in guard cells.

Test

Q.23 Hard Plant Physiology

During the S-state transitions in the oxygen-evolving complex, the manganese cluster undergoes sequential oxidation. How many oxidation steps occur before O2 is released?

A 2 steps

B 3 steps

C 4 steps

D 5 steps

Correct Answer: C. 4 steps

EXPLANATION

The Kok cycle involves S0→S1→S2→S3→S4 states. Four electrons are removed sequentially from the Mn4CaO5 cluster before O2 is released at the S4→S0 transition.

Test

Q.24 Hard Plant Physiology

The Emerson effect demonstrates that photosynthesis efficiency increases when plants are exposed to both red and far-red light together compared to either alone. This is explained by:

A Additive ATP production from both wavelengths

B Both photosystems working sequentially in series

C Synergistic activation of RuBisCO

D Reduced photorespiration under combined wavelengths

Correct Answer: B. Both photosystems working sequentially in series

EXPLANATION

The Emerson effect revealed the existence of two photosystems. Both PSI and PSII need to function sequentially for optimal electron transport and ATP/NADPH generation.

Test

Q.25 Hard Plant Physiology

Which photosystem has a lower reduction potential for its reaction center chlorophyll (P700 vs P680)?

A Photosystem I (P700)

B Photosystem II (P680)

C Both have identical reduction potentials

D Reduction potential varies with wavelength

Correct Answer: A. Photosystem I (P700)

EXPLANATION

P700 (PSI) has a lower (more negative) reduction potential than P680 (PSII), making it easier to reduce and better suited for final electron acceptance and NADP+ reduction.

Test

Q.26 Hard Plant Physiology

In the absence of light, what happens to the pH gradient across the thylakoid membrane?

A pH gradient increases rapidly

B pH gradient decreases as protons leak back

C pH gradient remains constant indefinitely

D pH becomes uniform across the membrane within seconds

Correct Answer: B. pH gradient decreases as protons leak back

EXPLANATION

Without light-driven electron transport, no new protons are pumped into the thylakoid lumen. The existing gradient dissipates as protons leak back through ATP synthase or other pathways.

Test

Q.27 Hard Plant Physiology

A plant is kept in a chamber with elevated CO2 concentration (800 ppm) and saturating light. What will be the most likely effect on the RuBP level in the stroma?

A RuBP levels will increase significantly

B RuBP levels will decrease due to increased carboxylation

C RuBP levels remain unchanged

D RuBP will be completely depleted

Correct Answer: B. RuBP levels will decrease due to increased carboxylation

EXPLANATION

Higher CO2 increases the carboxylation of RuBP to form 3-PG faster, consuming RuBP more rapidly. As long as the reduction phase can regenerate RuBP, levels may remain relatively stable, but the consumption rate increases.

Test

Q.28 Hard Plant Physiology

Which statement about ATP synthase is correct?

A It synthesizes ATP using proton gradient energy

B It functions in both photosynthesis and aerobic respiration

C The F0 subunit is embedded in the membrane

D All of the above are correct

Correct Answer: D. All of the above are correct

EXPLANATION

ATP synthase works in both processes using chemiosmotic gradient; F0 is the membrane-spanning unit; F1 synthesizes ATP from ADP.

Test

Q.29 Hard Plant Physiology

Which of the following best describes the Pasteur effect?

A Inhibition of photosynthesis by high light intensity

B Inhibition of fermentation by aerobic respiration

C Enhancement of fermentation under anaerobic conditions

D Increased photosynthesis at high CO2 levels

Correct Answer: B. Inhibition of fermentation by aerobic respiration

EXPLANATION

The Pasteur effect describes how aerobic respiration inhibits the rate of fermentation, as aerobic respiration is more efficient.

Test

Q.30 Hard Plant Physiology

The rate-limiting step of photosynthesis under normal conditions is:

A Light absorption

B CO2 fixation

C Electron transport

D Water photolysis

Correct Answer: B. CO2 fixation

EXPLANATION

The carboxylation of RuBP by RuBisCO is typically the slowest step in photosynthesis under normal light conditions.

Test

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