1. What triggers the opening of stomata during the day?
A) Low light intensity
B) High carbon dioxide levels
C) High light intensity
D) High oxygen levels
Answer: C) High light intensity
2. Which ion is actively transported into guard cells to facilitate stomatal opening?
A) Sodium ions
B) Calcium ions
C) Potassium ions
D) Magnesium ions
Answer: C) Potassium ions
3. The closure of stomata is typically associated with:
A) Increase in guard cell turgor
B) Decrease in guard cell turgor
C) High photosynthetic activity
D) Increase in potassium ions
Answer: B) Decrease in guard cell turgor
4. What is the main role of abscisic acid (ABA) in stomatal regulation?
A) Promotes stomatal opening
B) Triggers stomatal closure
C) Increases potassium uptake
D) Enhances photosynthesis
Answer: B) Triggers stomatal closure
5. The osmotic movement of water into guard cells is due to:
A) Decrease in solute concentration
B) Increase in solute concentration
C) Active transport of water
D) Passive diffusion of water
Answer: B) Increase in solute concentration
6. Which structural feature of guard cells is crucial for stomatal movement?
A) Thick outer walls
B) Thin outer walls
C) Thick inner walls
D) Thin inner walls
Answer: C) Thick inner walls
7. During stomatal opening, the pH inside guard cells typically:
A) Increases
B) Decreases
C) Remains constant
D) Becomes neutral
Answer: A) Increases
8. What happens to guard cell starch during stomatal opening?
A) It is synthesized
B) It is hydrolyzed to sugar
C) It remains unchanged
D) It forms lipid droplets
Answer: B) It is hydrolyzed to sugar
9. Which environmental factor does NOT directly influence stomatal movement?
A) Light intensity
B) Soil composition
C) Humidity levels
D) Carbon dioxide concentration
Answer: B) Soil composition
10. Stomatal closing occurs at night mainly due to:
A) High light intensity
B) Low photosynthetic activity
C) Low oxygen concentration
D) High humidity levels
Answer: B) Low photosynthetic activity
11. The opening of stomata helps in:
A) Absorption of nutrients
B) Gaseous exchange
C) Root water uptake
D) Chlorophyll synthesis
Answer: B) Gaseous exchange
12. Potassium ions move into guard cells through:
A) Osmosis
B) Diffusion
C) Active transport
D) Facilitated diffusion
Answer: C) Active transport
13. What is the role of chloroplasts in guard cells?
A) Synthesizing starch
B) Producing energy for ion transport
C) Preventing water loss
D) Facilitating gas exchange
Answer: B) Producing energy for ion transport
14. Which ion efflux contributes to stomatal closure?
A) Potassium ions
B) Calcium ions
C) Chloride ions
D) Sodium ions
Answer: A) Potassium ions
15. Water movement out of guard cells is due to:
A) Decrease in solute concentration
B) Increase in solute concentration
C) Osmotic pressure
D) High humidity
Answer: A) Decrease in solute concentration
16. What happens to stomata under water stress conditions?
A) They open fully
B) They close partially
C) They remain open
D) They close completely
Answer: D) They close completely
17. The ion pump involved in stomatal movement is:
A) ATPase pump
B) Sodium-potassium pump
C) Proton pump
D) Calcium pump
Answer: C) Proton pump
18. Guard cells are regulated by:
A) Mesophyll cells
B) Environmental signals
C) Xylem sap flow
D) Stomatal subsidiary cells
Answer: B) Environmental signals
19. During stomatal opening, the guard cell wall expands more on the:
A) Outer side
B) Inner side
C) Both sides equally
D) Does not expand
Answer: A) Outer side
20. Which molecule accumulates during stomatal opening?
A) Glucose
B) ATP
C) Malate
D) Oxygen
Answer: C) Malate
21. What is the primary driver for the influx of potassium ions into guard cells?
A) Light activation
B) Temperature changes
C) Gravity
D) Abscisic acid concentration
Answer: A) Light activation
22. Why do stomata close during the daytime in some plants?
A) To prevent oxygen loss
B) To reduce water loss
C) To enhance photosynthesis
D) To absorb more sunlight
Answer: B) To reduce water loss
23. Which hormone counteracts the effect of abscisic acid on stomata?
A) Auxin
B) Gibberellin
C) Cytokinin
D) Ethylene
Answer: C) Cytokinin
24. When stomata close, what happens to photosynthesis?
A) It increases
B) It decreases
C) It remains constant
D) It becomes anaerobic
Answer: B) It decreases
25. Stomatal movement is an example of:
A) Passive transport
B) Active transport
C) Facilitated diffusion
D) Simple osmosis
Answer: B) Active transport
26. Which condition would likely keep stomata closed?
A) High light intensity
B) High humidity
C) Low water availability
D) High carbon dioxide inside the leaf
Answer: C) Low water availability
27. What structural feature helps guard cells bend during opening?
A) Unevenly thickened walls
B) Lack of cellulose
C) Presence of lignin
D) Radial symmetry
Answer: A) Unevenly thickened walls
28. Which pathway primarily regulates ion movement in guard cells?
A) Glycolytic pathway
B) Calvin cycle
C) Signal transduction pathways
D) Photosystem II pathway
Answer: C) Signal transduction pathways
29. Stomatal opening enhances:
A) CO2 uptake
B) Oxygen release
C) Water uptake
D) Both A and B
Answer: D) Both A and B
30. The immediate effect of ABA on guard cells is to:
A) Increase potassium influx
B) Increase potassium efflux
C) Decrease ATP production
D) Increase oxygen concentration
Answer: B) Increase potassium efflux
