Showing 31–40 of 207 questions
Which of the following is the primary pigment responsible for absorbing light energy in the visible spectrum during photosynthesis?
A
Chlorophyll a
B
Xanthophyll
C
Carotenoid
D
Anthocyanin
Correct Answer:
A. Chlorophyll a
Explanation:
Chlorophyll a is the primary photosynthetic pigment that absorbs light in the blue and red regions of the electromagnetic spectrum.
The pH of cell sap in plant cells typically ranges between:
Explanation:
Plant cell sap is slightly acidic due to organic acids like malic acid and citric acid, maintaining pH between 4-6.
Which element is essential for the synthesis of chlorophyll molecule and forms the central atom in its structure?
A
Iron
B
Magnesium
C
Zinc
D
Copper
Correct Answer:
B. Magnesium
Explanation:
Magnesium (Mg) is the central atom in the chlorophyll molecule, forming a coordinate bond with the porphyrin ring.
The phenomenon where plants bend towards light source is governed by which hormone?
A
Gibberellin
B
Auxin
C
Cytokinin
D
Ethylene
Explanation:
Auxin causes differential elongation of cells on the shaded side, resulting in phototropic response towards light.
In C4 plants, the first stable compound formed during carbon fixation is:
A
3-Phosphoglycerate
B
Oxaloacetate
C
Ribulose-1,5-bisphosphate
D
Glucose
Correct Answer:
B. Oxaloacetate
Explanation:
In C4 photosynthesis, CO2 combines with PEP (3-carbon) to form oxaloacetate (4-carbon compound) via the enzyme PEP carboxylase.
The root pressure phenomenon in plants can be measured using a device called:
A
Potometer
B
Barograph
C
Manometer
D
Tensiometer
Correct Answer:
C. Manometer
Explanation:
Root pressure is measured using a manometer connected to the cut end of a plant stem, showing the positive pressure generated by roots.
Which of the following statements about stomatal opening is correct?
A
Guard cells lose turgor pressure when stomata open
B
Potassium ions accumulate in guard cells during stomatal opening
C
Stomata open in complete darkness
D
Guard cells have thick outer walls and thin inner walls
Correct Answer:
B. Potassium ions accumulate in guard cells during stomatal opening
Explanation:
During stomatal opening, potassium ions (K+) actively accumulate in guard cells, increasing osmotic potential and causing water influx.
The phenomenon of leaf fall in deciduous plants before winter is regulated by which hormone?
A
Abscisic acid
B
Ethylene
C
Gibberellin
D
Cytokinin
Correct Answer:
A. Abscisic acid
Explanation:
Abscisic acid (ABA) accumulates during water stress and environmental changes, promoting abscission layer formation and leaf fall.
In plant tissue culture, which growth regulator ratio promotes callus formation?
A
High auxin : Low cytokinin
B
Low auxin : High cytokinin
C
Equal ratio of auxin and cytokinin
D
Neither auxin nor cytokinin
Correct Answer:
A. High auxin : Low cytokinin
Explanation:
High auxin to low cytokinin ratio promotes callus formation, while the ratios determine the type of organogenesis.
The osmotic potential of a solution is directly related to:
A
Temperature only
B
Solute concentration and temperature
C
Pressure only
D
Volume of solvent only
Correct Answer:
B. Solute concentration and temperature
Explanation:
Osmotic potential (Ψs) = -iCRT, where it depends on solute concentration (C) and absolute temperature (T).
