They flower when daylight hours are long.

They flower when daylight hours are long.

• A. They flower when daylight hours are short.
• B. They flower randomly regardless of day length.
• C. They never flower due to day length.
• D. They flower when daylight hours are long and require long daylight to flower.

Answer: (C)

Photoperiodism governs when many plants flower based on day length. Long-day plants need days longer than a certain duration to trigger flowering, typically flowering in late spring or early summer when daylight is extended. Saying they flower when daylight hours are long describes this pattern: the plant responds to long days by initiating flowering once the light period crosses its threshold. This is opposed to short-day plants, which require longer nights to flower, or day-neutral plants that don’t rely on day length, or cases where flowering never occurs due to photoperiod.

Photoperiodism governs when many plants flower based on day length. Long-day plants need days longer than a certain duration to trigger flowering, typically flowering in late spring or early summer when daylight is extended. Saying they flower when daylight hours are long describes this pattern: the plant responds to long days by initiating flowering once the light period crosses its threshold. This is opposed to short-day plants, which require longer nights to flower, or day-neutral plants that don’t rely on day length, or cases where flowering never occurs due to photoperiod.