1. What is photoperiodism in plants?
A) Response to temperature
B) Response to light intensity
C) Response to light duration
D) Response to humidity
Answer: C) Response to light duration
Explanation: Photoperiodism refers to the physiological response of plants to the length of day and night. It regulates processes such as flowering.
2. Which of the following is a short-day plant?
A) Wheat
B) Soybean
C) Chrysanthemum
D) Lettuce
Answer: C) Chrysanthemum
Explanation: Short-day plants flower when the night length exceeds a critical period, typically when the day length is shorter.
3. What is the role of phytochromes in photoperiodism?
A) They absorb sunlight
B) They help in regulating the plant’s response to light
C) They prevent photosynthesis
D) They increase the length of days
Answer: B) They help in regulating the plant’s response to light
Explanation: Phytochromes are light-sensitive proteins that detect light and help regulate responses such as flowering in plants.
4. Which type of plant requires a long day to flower?
A) Long-day plants
B) Short-day plants
C) Day-neutral plants
D) All of the above
Answer: A) Long-day plants
Explanation: Long-day plants require longer daylight to trigger flowering, typically when the night length is shorter.
5. What is the critical night length for a short-day plant to flower?
A) Less than 12 hours
B) More than 12 hours
C) Exactly 12 hours
D) There is no fixed critical night length
Answer: B) More than 12 hours
Explanation: Short-day plants require longer nights (more than 12 hours) to flower.
6. Which pigment is involved in detecting light for photoperiodism?
A) Chlorophyll
B) Carotenoids
C) Phytochrome
D) Xanthophyll
Answer: C) Phytochrome
Explanation: Phytochromes are pigments that help plants detect light and regulate processes like flowering based on the length of day and night.
7. In which of the following is photoperiodism least important?
A) Flowering in plants
B) Leaf growth
C) Germination
D) Fruit development
Answer: B) Leaf growth
Explanation: Leaf growth is primarily regulated by other factors like water and nutrient availability, not photoperiodism.
8. What type of plants flower irrespective of day length?
A) Long-day plants
B) Short-day plants
C) Day-neutral plants
D) Photoperiod-sensitive plants
Answer: C) Day-neutral plants
Explanation: Day-neutral plants flower regardless of the day length, as their flowering is not controlled by photoperiod.
9. Which hormone is involved in the regulation of photoperiodism?
A) Cytokinin
B) Gibberellin
C) Auxin
D) Florigen
Answer: D) Florigen
Explanation: Florigen is a hormone-like protein that is believed to be involved in the induction of flowering in response to light cues.
10. Which of the following factors affects the photoperiodic response in plants?
A) Soil moisture
B) Temperature
C) Daylight duration
D) Carbon dioxide levels
Answer: C) Daylight duration
Explanation: Photoperiodism is primarily influenced by the duration of light exposure (daylight) and the length of the night.
11. What is the effect of light interruption on short-day plants?
A) It has no effect
B) It delays flowering
C) It induces immediate flowering
D) It promotes vegetative growth
Answer: B) It delays flowering
Explanation: Light interruption during the night (interrupted darkness) can disrupt the photoperiod and delay flowering in short-day plants.
12. In which season do long-day plants typically flower?
A) Summer
B) Winter
C) Spring
D) Fall
Answer: A) Summer
Explanation: Long-day plants typically flower during the summer months when the days are long, and the nights are short.
13. What happens when a long-day plant is exposed to less light than the critical photoperiod?
A) It flowers early
B) It does not flower
C) It enters dormancy
D) It produces more leaves
Answer: B) It does not flower
Explanation: If the exposure to light is less than the critical photoperiod, long-day plants will not flower as they require long days to trigger flowering.
14. Which of these is an example of a long-day plant?
A) Spinach
B) Poinsettia
C) Tobacco
D) Begonia
Answer: C) Tobacco
Explanation: Tobacco is a long-day plant that requires longer daylight to flower.
15. What is the typical effect of photoperiodism in plants?
A) Germination control
B) Growth rate modulation
C) Flowering time regulation
D) Root system growth
Answer: C) Flowering time regulation
Explanation: Photoperiodism mainly regulates flowering time based on the length of the day and night.
16. Which of the following is NOT a type of photoperiodic plant?
A) Short-day plants
B) Long-day plants
C) Day-neutral plants
D) Winter plants
Answer: D) Winter plants
Explanation: “Winter plants” is not a recognized category of photoperiodic plants. The main categories are short-day, long-day, and day-neutral plants.
17. What is the role of red light in photoperiodism?
A) It inhibits flowering
B) It promotes flowering in short-day plants
C) It promotes flowering in long-day plants
D) It has no effect
Answer: C) It promotes flowering in long-day plants
Explanation: Red light is important for promoting flowering in long-day plants by helping them detect the duration of day and night.
18. Which of the following would be least affected by photoperiodism?
A) A plant’s flowering time
B) A plant’s height
C) A plant’s seed formation
D) A plant’s leaf production
Answer: D) A plant’s leaf production
Explanation: Leaf production is generally not regulated by photoperiodism, while flowering time, seed formation, and growth patterns can be.
19. What is the critical role of phytochrome in photoperiodism?
A) It helps plants absorb nutrients
B) It regulates chlorophyll production
C) It detects light duration and induces flowering
D) It helps in water uptake
Answer: C) It detects light duration and induces flowering
Explanation: Phytochrome detects the light duration and helps initiate the flowering response in photoperiodic plants.
20. Which of the following plants is classified as a short-day plant?
A) Tulip
B) Rice
C) Cotton
D) Soybean
Answer: D) Soybean
Explanation: Soybean is a short-day plant that requires a longer night period to flower.
21. What is the function of the phytochrome pigment in plants?
A) Absorbing sunlight
B) Regulating photosynthesis
C) Perceiving light and regulating growth
D) Stimulating root development
Answer: C) Perceiving light and regulating growth
Explanation: Phytochrome pigments help plants perceive light and regulate growth processes, including flowering and photoperiodism.
22. How can artificial light affect photoperiodic responses?
A) It can delay flowering in long-day plants
B) It can shorten the flowering time of short-day plants
C) It has no impact
D) It can replace natural light for photoperiodic response
Answer: A) It can delay flowering in long-day plants
Explanation: Artificial light during the night can disrupt the photoperiodic response, particularly in long-day plants, delaying their flowering.
23. Which of the following plants flowers only after receiving a long period of darkness?
A) Roses
B) Poinsettias
C) Tulips
D) Daffodils
Answer: B) Poinsettias
Explanation: Poinsettias are short-day plants and require a long period of darkness to flower.
24. How does temperature interact with photoperiodism?
A) It is unrelated to photoperiodism
B) It affects the light sensitivity of plants
C) It regulates night duration
D) It directly influences the chlorophyll levels
Answer: B) It affects the light sensitivity of plants
Explanation: Temperature can influence the photoperiodic sensitivity of plants and may interact with light to regulate flowering.
25. What does the term “critical photoperiod” refer to?
A) The minimum temperature for flowering
B) The required light intensity
C) The minimum night length required for flowering
D) The amount of rainfall needed for flowering
Answer: C) The minimum night length required for flowering
Explanation: The critical photoperiod refers to the specific duration of the night that plants require for flowering.
26. What is an example of a day-neutral plant?
A) Wheat
B) Tomato
C) Rose
D) Cabbage
Answer: B) Tomato
Explanation: Day-neutral plants, like tomatoes, flower regardless of the photoperiod.
27. What is the role of florigen in photoperiodism?
A) It inhibits photosynthesis
B) It promotes seed germination
C) It induces flowering in response to light signals
D) It helps in leaf expansion
Answer: C) It induces flowering in response to light signals
Explanation: Florigen is a hormone-like substance that is believed to trigger flowering in response to photoperiodic cues.
28. What happens when long-day plants are exposed to extended periods of darkness?
A) They continue to grow but do not flower
B) They flower immediately
C) They produce more leaves
D) They do not flower
Answer: A) They continue to grow but do not flower
Explanation: Long-day plants require extended periods of light, and prolonged darkness can prevent flowering.
29. Which of the following factors primarily triggers flowering in long-day plants?
A) Temperature
B) Soil moisture
C) Length of daylight
D) Rainfall
Answer: C) Length of daylight
Explanation: Long-day plants flower when the duration of daylight exceeds a certain critical period.
30. Why do plants respond to light in terms of photoperiodism?
A) To optimize energy use
B) To control their flowering cycle
C) To regulate seed germination
D) To produce more chlorophyll
Answer: B) To control their flowering cycle
Explanation: Photoperiodism helps plants synchronize their flowering with optimal environmental conditions, ensuring successful reproduction.
