Which type of phloem tissue is responsible for translocation of sugars in plants?
A
Sieve tube members only
B
Companion cells only
C
Sieve tube members with companion cells
D
Phloem fibers
Correct Answer:
C. Sieve tube members with companion cells
Explanation:
Sieve tube members conduct sugars while companion cells provide ATP and metabolic support for active transport.
The process by which plants lose water as water vapour through stomata is called:
A
Guttation
B
Transpiration
C
Imbibition
D
Exudation
Correct Answer:
B. Transpiration
Explanation:
Transpiration is the loss of water vapour from aerial parts of plants, primarily through stomata during daytime.
In the light-dependent reactions, the splitting of water molecules produces oxygen, hydrogen ions, and:
A
NADP+
B
NADPH
C
Electrons
D
ATP alone
Correct Answer:
C. Electrons
Explanation:
Water photolysis (2H2O → O2 + 4H+ + 4e-) releases electrons that are transferred through electron transport chains.
The enzyme RuBisCO catalyzes the fixation of CO2 by combining it with:
A
Glyceraldehyde-3-phosphate
B
Ribulose-1,5-bisphosphate
C
Phosphoenolpyruvate
D
Pyruvate
Correct Answer:
B. Ribulose-1,5-bisphosphate
Explanation:
RuBisCO (Ribulose-1,5-bisphosphate carboxylase/oxygenase) catalyzes CO2 fixation with RuBP in the Calvin cycle.
Which of the following plants exhibits CAM (Crassulacean Acid Metabolism) photosynthesis?
A
Wheat
B
Rice
C
Pineapple
D
Maize
Correct Answer:
C. Pineapple
Explanation:
CAM plants like pineapple, cactus, and agave fix CO2 at night into organic acids and release during day for photosynthesis.
The pulling force that moves water upward in xylem vessels is primarily due to:
A
Root pressure alone
B
Capillary action alone
C
Transpirational pull (tension) in xylem
D
Gravitational force
Correct Answer:
C. Transpirational pull (tension) in xylem
Explanation:
Cohesion-tension theory explains that water is pulled upward due to transpirational pull creating negative pressure in xylem.
In the nitrogen cycle, the conversion of atmospheric N2 into ammonia is carried out by:
A
Nitrosomonas
B
Rhizobium
C
Nitrobacter
D
Thiobacillus
Correct Answer:
B. Rhizobium
Explanation:
Rhizobium bacteria in root nodules of legumes fix atmospheric nitrogen into ammonia through nitrogenase enzyme.
When a plant wilts despite adequate soil moisture, this condition is called:
A
Permanent wilting point
B
Incipient wilting
C
Physiological wilting
D
Hydration stress
Correct Answer:
C. Physiological wilting
Explanation:
Physiological wilting occurs when transpiration rate exceeds water absorption rate, though soil moisture is sufficient.
The double fertilization process in angiosperms results in the formation of:
A
Seed coat and cotyledon
B
Endosperm and embryo
C
Fruit and seed
D
Ovule and nucellus
Correct Answer:
B. Endosperm and embryo
Explanation:
Double fertilization: one sperm fuses with egg nucleus (embryo), other fuses with polar nuclei (endosperm - 3n).
A plant cell is placed in a hypertonic solution. Which physical phenomenon occurs, and what is the correct term for it?
A
Plasmolysis - protoplasm shrinks away from cell wall
B
Deplasmolysis - cell regains water
C
Turgor pressure increases
D
Cell wall becomes permeable
Correct Answer:
A. Plasmolysis - protoplasm shrinks away from cell wall
Explanation:
In hypertonic solutions, water moves out of the cell due to osmosis, causing protoplasm to shrink away from the cell wall - this is plasmolysis. This is a fundamental osmotic principle tested in SSC/Railway exams.
