Question

The critical photoperiod for two flowering plants X and Y are 10 hours. At 14 hours of light per day, plant X flowers but there are no flowers on Y. Can you categorize the two plants according to their photoperiodic response?

• A. X- Short day plant, Y- Long day plant
• B. X-Long day plant, Y-Short day plant
• C. X-Short day plant, Y-Day neutral plant
• D. X- Long day plant, Y-Day neutral plant

Answer 1

The correct option is B X-Long day plant, Y-Short day plant

Photoperiodism is the response of plants to the relative length of day and night. The length of the day or duration of light during the day is called the light period or photoperiod. This periodic exposure of light leads to flowering in some plants. Certain plants require a definite photoperiod to induce flowering called a critical photoperiod. Based on this, the plants are divided into:

i. Long day plants: These are those plants that require a longer period of light than a critical photoperiod.

ii. Short-day plants: These are those plants that require a shorter period of light than a critical photoperiod.

iii. Day-neutral plants: The flowering in these plants is not affected by the exposure to light duration.

Plant X has a critical photoperiod of 10 hours. It flowered on exposure to a period of light of 14 hours. Therefore, it is a long day plant.

Plant Y has a critical photoperiod of 10 hours. It could not flower on exposure to a period of light of 14 hours. Therefore, it is a short day plant.