Which of the following statements about stomatal conductance is correct?
Answer: C
Stomatal conductance (gs) is the rate of gas diffusion through stomata, dependent on aperture width and inversely on distance (g = A/L).
Q.82Medium
The Hatch-Slack cycle in C4 plants first produces which compound?
Answer: A
In C4 photosynthesis, CO₂ combines with phosphoenolpyruvate (PEP) to form oxaloacetate (4-carbon), catalyzed by PEP carboxylase.
Q.83Easy
The phenomenon of etiolation in plants is characterized by:
Answer: B
Etiolation is the adaptation to grow in darkness: shoots elongate, leaves remain pale (no chlorophyll), and seedlings appear yellowish.
Q.84Medium
The transpiration pull mechanism in xylem transport depends on which principle?
Answer: B
Transpiration creates negative pressure (tension) in xylem; water cohesion allows continuous columns to be pulled upward against gravity.
Q.85Easy
Which plant hormone promotes fruit ripening and is commercially used in India for tomato and mango maturation?
Answer: B
Ethylene (C₂H₄) is the ripening hormone that triggers color change, softening, and aroma development in climacteric fruits.
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Q.86Medium
The non-cyclic photophosphorylation in photosystem II produces:
Answer: C
Non-cyclic photophosphorylation involves PSII and PSI, producing ATP, NADPH, and O₂ from water photolysis.
Q.87Hard
In the electron transport chain of chloroplasts, which complex transfers electrons from water to plastoquinone?
Answer: B
PSII catalyzes photolysis of water at the oxygen-evolving complex, transferring electrons to plastoquinone in the thylakoid membrane.
Q.88Easy
The double fertilization process unique to angiosperms results in the formation of:
Answer: A
One sperm nucleus fertilizes the egg (embryo), another fuses with polar nuclei (endosperm); this endosperm provides nutritive tissue for the developing embryo.
Q.89Easy
Which of the following is the primary pigment responsible for capturing light energy in photosynthesis?
Answer: A
Chlorophyll a is the primary pigment that directly participates in the light reactions of photosynthesis and forms the reaction centre of both photosystems.
Q.90Medium
The reduction phase of Calvin cycle produces which molecule as the final product?
Answer: C
G3P (Glyceraldehyde-3-phosphate) is the final product of the reduction phase where 3-PG is reduced using ATP and NADPH from light reactions.
Q.91Medium
C3 plants show a phenomenon of photorespiration. What is the primary substrate that reacts with RuBP when O2 concentration is high?
Answer: C
When O2 concentration is high, RuBisCO catalyzes oxygenase activity, causing O2 to react with RuBP instead of CO2, initiating photorespiration.
Q.92Easy
Which statement about stomata is INCORRECT?
Answer: B
Stomata open during the day (when light is available for photosynthesis) and close at night. This reduces water loss during low photosynthetic activity periods.
Q.93Hard
In the light-dependent reactions, where exactly does the photolysis of water occur?
Answer: B
Water photolysis occurs in the thylakoid lumen as part of Photosystem II, releasing O2, H+, and electrons that drive the electron transport chain.
Q.94Easy
Which of the following is a C4 plant commonly found in tropical regions?
Answer: C
Sugarcane is a C4 plant adapted to high light and temperature conditions. C4 plants first fix CO2 into a 4-carbon compound (oxaloacetate).
Q.95Medium
The phenomenon where plants lose water as liquid droplets from leaf margins is called:
Answer: B
Exudation or guttation occurs when root pressure forces water out through specialized pores (hydathodes) as liquid water droplets, typically observed in early morning.
Q.96Medium
Which plant hormone is known to have antagonistic effects to gibberellins in seed germination?
Answer: B
Abscisic acid (ABA) promotes seed dormancy and inhibits germination, acting antagonistically to gibberellins which promote germination.
Q.97Hard
The ratio of ATP to NADPH consumed in the Calvin cycle is:
Answer: C
For every 3 turns of Calvin cycle (fixing 3 CO2), 9 ATP and 6 NADPH are used. This gives a ratio of 3:2 (ATP:NADPH).
Q.98Medium
Which of the following transport mechanisms does NOT require energy in plant cells?
Answer: B
Osmosis is passive transport of water molecules across a semipermeable membrane in response to water potential differences.
Q.99Hard
The Casparian strip in the endodermis of roots is primarily composed of:
Answer: B
The Casparian strip contains suberin (waxy substance) and lignin, which prevents apoplastic (cell wall) movement of water and minerals, forcing symplastic transport.
Q.100Easy
Which organelle is responsible for the synthesis of ribosomal RNA in plant cells?
Answer: B
The nucleolus within the nucleus is the site of ribosomal RNA (rRNA) synthesis and ribosome assembly in eukaryotic cells.
