Question

Chrysanthemum flowers either in winter or in evening because it is a
A. Short-day plant
B. Long-day plant
C. Day-neutral plant
D. Mid-day plant

Answer 1

Hint:-The ability to flower of a plant depends on many factors. The one factor among them is the photoperiod. The responsiveness of any plant towards changes in photoperiod is called photoperiodism. To answer this question, we will first try to understand the effect of photoperiodism on the flowering of plants. Then, we will find the correct answer.

Complete answer:
Step 1: Let us first understand the effect of photoperiodism on the flowering of plants.
Photoreceptor proteins such as phytochromes or cryptochromes, are used by many flowering plants as a sensory mechanism to seasonal changes in the photoperiod. Phytochromes come in two different forms- pr and pfr. pfr is the active form while pr is the inactive form of phytochromes. During the day time, plant growth is triggered as the red light converts the phytochrome to its active form pfr. On the other hand, in the dark, far-red light converts pfr to an inactive form called pr which inhibits the growth of plants. This phenomenon has a significant impact on the flowering of plants and by manipulating the ratio of red-to-far-red, flowering can be altered. It has been observed that cryptochromes and phytochromes abundance can be altered by changing the photoperiod.
Step 2: Based on photoperiodism, plants are classified as-
Short-day plants- They are also known as long-night plants as they cannot flower under periods of shorter nights or in the pulse of artificial light for a longer duration in the night. They flower when their critical photoperiod is exceeded by the length of the night. In a nutshell, these plants require prolonged periods of darkness before they can commence floral development.
Long-day plants- As the name suggests, they require longer day lengths for flowering. They generally flower when the length of night is too short that it falls below the critical photoperiod.
Day- neutral plants- They are not photoperiodism- dependent for the flowering initiation. Rather, their flowering is dependent on other factors such as the stage of development they are in and certain environmental stimuli such as vernalization, etc.
Step 2: Chrysanthemum and flowering-
Chrysanthemum requires longer night periods before they can commence flowering. They generally require 11 to 12 hours or longer duration of darkness (the exact variation may vary according to the cultivar). Thus, they prefer to grow during winter or in the evening.
Step 3: From the above explanation, it is clear that the correct answer is (A)- Short-day plant.

Note:- Chrysanthemum is sometimes subjected to blackout systems to initiate rapid flowering as compared to that when they would flower under normal shortening conditions.
Chrysanthemum has significant medicinal properties and used to treat chest pain, type 2 diabetes, high blood pressure, fever, headache, cold, swelling, and dizziness. It can also be used to treat prostate cancer when it is combined with other herbs.