Question

The long-day plant is
(a) Tomato
(b) Potato
(c ) Cotton
(d) Spinach

Answer 1

Plants respond differently to different durations of day and night. This relative duration of day and night is known as photoperiod. It affects flowering in angiosperms. The long day plant in the options is rich in iron.

Complete answer:
The flowering of angiosperms is dependent on this phenomenon of photoperiodism. Based on their response, they are of three types namely long-day plants, short-day plants, and day-neutral plants. Long day plants are the ones that require light for a period exceeding a well-defined critical duration. E.g. Hibiscus, spinach, radish, etc. The long day plants are also known as short-night plants. They flower in the spring or early summer.

Additional Information:
- Short day plants are those plants which are exposed to light for a period less than the critical duration before the flowering is initiated in them. E.g. Cotton, rice, etc.
- Day-neutral plants are the ones where no relationship between exposure to light duration and induction of flowering response occurs. These include tomato, potato, etc.
- The duration of light and duration of dark have also equal importance in plants. The site of perception of light/dark duration is leaves.
- Photoperiodism is sensed by a hormonal substance that migrates from leaves to shoot apices where it will induce flowering after a critical duration of light is achieved.
So, the correct answer is ‘(d) Spinach.’

Note: Photoperiodism is also observed in animals but the effects are not as drastic or dependent as in plants. Some animals are dependent on duration for light for seasonal behavior strategies that aid in their better survivability. These seasonal behaviors include seasonal breeding and diapause in insects etc.