Showing 71–76 of 76 questions
in Plant Physiology
Which of the following statements about transpiration is correct?
A
Transpiration increases with increase in humidity
B
Transpiration is independent of temperature
C
Transpiration increases with decrease in humidity
D
Transpiration occurs only through stomata
Correct Answer:
C. Transpiration increases with decrease in humidity
EXPLANATION
Transpiration increases with decrease in humidity as the vapor pressure gradient between leaf and atmosphere increases.
In C4 plants, the first stable compound formed during photosynthesis is:
A
3-phosphoglycerate
B
Oxaloacetate
C
Glucose
D
Pyruvate
Correct Answer:
B. Oxaloacetate
EXPLANATION
In C4 plants, CO2 combines with PEP to form oxaloacetate (4-carbon compound) in the mesophyll cells, unlike C3 plants where 3-PGA is formed.
The dark reaction of photosynthesis does not require which of the following?
A
ATP
B
NADPH
C
Light
D
CO2
EXPLANATION
Dark reactions (Calvin cycle) do not directly require light; they use ATP and NADPH produced from light reactions to fix CO2.
Which pigment is responsible for absorbing light energy in photosystem II?
A
Chlorophyll b
B
Xanthophyll
C
P680 (Chlorophyll a)
D
Carotenoid
Correct Answer:
C. P680 (Chlorophyll a)
EXPLANATION
P680 is a special chlorophyll a molecule in the reaction center of PSII that absorbs light at 680 nm wavelength.
The rate of photosynthesis is maximum at which wavelength of light?
A
400-500 nm (Blue)
B
600-700 nm (Red)
C
500-600 nm (Green)
D
700-800 nm (Far red)
Correct Answer:
B. 600-700 nm (Red)
EXPLANATION
Red light (600-700 nm) is most effectively used in photosynthesis, followed by blue light. Green light is poorly absorbed.
Which of the following is the primary source of energy for plant cells?
A
Photosynthesis
B
Chemosynthesis
C
Cellular respiration
D
Fermentation
Correct Answer:
A. Photosynthesis
EXPLANATION
Photosynthesis is the primary source of energy for plant cells as it converts light energy into chemical energy in the form of glucose.
