Question

Choose the correct answer from the alternatives given.
If a long-day plant has a critical night length of 9 hours then which of the following 24-hour cycles would prevent flowering:

• A. 16 hours light/8 hours dark
• B. 14 hours light/10 hours dark
• C. 4 hours light/8 hours dark/4 hours light/8 hours dark
• D. 8 hours light/8 hours dark/light flash/8 hours dark

Answer 1

The correct option is B 14 hours light/10 hours dark

The critical photoperiod is the continuous duration of light which should not be exceeded in short day plants but should always be exceeded in long day plants. Here the critical night length for the long day plants are 9 hours which should more and the light phase should be smaller.

So, the correct option is '14 hours light/10 hours dark'.