Showing 71–78 of 78 questions
in Botany
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 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.
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 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.
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 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 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.
Photosynthesis occurs in?
A
Root
B
Stem
C
Leaf
D
Flower
EXPLANATION
In chloroplasts of leaves.
