Which of the following organelles is responsible for synthesizing ATP through oxidative phosphorylation in plant cells?
Answer: A
Mitochondria is the powerhouse of the cell and produces ATP through oxidative phosphorylation. Chloroplasts produce ATP through photophosphorylation.
Q.42Medium
The calcium pump in plant cell vacuole membrane is primarily involved in:
Answer: C
Calcium pumps actively transport Ca²⁺ into vacuoles, serving as a calcium reservoir for second messenger signaling in plant cells.
Q.43Easy
During C3 photosynthesis, the first stable product formed after CO₂ fixation is:
Answer: B
In the Calvin cycle, RuBP combines with CO₂ to form 3-PGA (3-carbon compound), which is the first stable product detected in C3 plants.
Q.44Easy
Which enzyme catalyzes the carboxylation of RuBP in the Calvin cycle, and what is its full name?
Answer: A
Rubisco is the most abundant enzyme on Earth and catalyzes both carboxylation (photosynthesis) and oxygenation (photorespiration) of RuBP.
Q.45Medium
The phenomenon where plants show reduced photosynthesis when exposed to high oxygen concentrations is called:
Answer: A
The Warburg effect in plants refers to photorespiration, where high O₂ competes with CO₂ for Rubisco binding, reducing net photosynthesis.
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Q.46Medium
Mycorrhizal associations in plants primarily enhance the uptake of which nutrients?
Answer: B
Arbuscular mycorrhizal fungi increase plant access to phosphorus and micronutrients (Zn, Cu) through their extensive hyphal networks in soil.
Q.47Medium
The casparian strip in plant roots is composed primarily of:
Answer: B
The casparian strip is a hydrophobic barrier of suberin and lignin in the endodermis that prevents apoplastic transport and regulates ion uptake.
Q.48Easy
Which of the following is a C4 plant commonly cultivated in India for fodder and grain production?
Answer: B
Maize is a C4 plant with higher photosynthetic efficiency and drought tolerance compared to C3 crops like wheat and rice.
Q.49Medium
The quantum yield of photosynthesis (φ) represents:
Answer: A
Quantum yield is the ratio of CO₂ fixed to photons absorbed, typically 0.05-0.1 (5-10 CO₂ per 100 photons).
Q.50Medium
Guttation in plants occurs due to:
Answer: B
Guttation is the exudation of xylem sap through hydathodes, caused by positive root pressure, especially in early morning when transpiration is low.
Q.51Medium
The turgor pressure in plant cells is maintained by which osmotically active substances?
Answer: B
Osmotically active solutes like glucose, sucrose, malate, and K⁺ ions accumulate in vacuoles to maintain turgor pressure and cell rigidity.
Q.52Hard
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.53Medium
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.54Easy
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.55Medium
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.56Easy
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.
Q.57Medium
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.58Hard
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.59Easy
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.60Easy
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.
