Which category of plants flowers when exposed to daylight hours shorter than a specific threshold?

Short-day plants are those that require daylight hours shorter than a certain threshold to trigger flowering. This response is primarily governed by the plant's internal biological clock and photoperiodism, which allows them to adapt their flowering according to seasonal changes in daylight.

These plants typically flower in late summer or early autumn, when days become shorter. They have evolved to synchronize their flowering with environmental conditions that are conducive to pollination and seed maturation, which often occur in the cooler, shorter days of fall. The mechanism involves the detection of light using a pigment called phytochrome, which helps the plant measure the duration of light and darkness.

In contrast, long-day plants flower when the daylight hours exceed a specific threshold, typically in late spring or early summer. Day-neutral plants are not significantly affected by day length and can flower regardless of the duration of light exposure. Perennial plants refer to those that live for multiple years and do not pertain directly to the photoperiodic cues for flowering. Thus, the identification of short-day plants as those that respond to shorter daylight periods is correct, reflecting a key aspect of their reproductive strategy.