It is well known that the daylength, or photoperiod, affects the flowering time of plants. However, the mechanisms by which this occurs are not well understood. It is thought that the photoperiod somehow alters the plant’s internal clock, or circadian rhythm, which controls the timing of flower development. The length of the day is an important factor in the timing of flower development in many plant species. In general, plants flower sooner when the days are shorter (i.e., in the spring) and later when the days are longer (i.e., in the summer). This phenomenon is called photoperiodism. The mechanism by which the photoperiod affects flower development is not well understood. It is thought that the photoperiod somehow alters the plant’s internal clock, or circadian rhythm. The circadian rhythm is an internal biological clock that regulates many plant processes, including the timing of flower development. Some plants are more sensitive to changes in the photoperiod than others. For example, short-day plants flower only when the days are shorter than a certain critical length, while long-day plants flower only when the days are longer than a certain critical length. The critical daylength differs among plant species, and even among different varieties of the same species. For example, the critical daylength for the common bean (Phaseolus vulgaris) is about 12 hours. This means that common beans will flower only when the days are shorter than 12 hours. The critical daylength also varies with the time of year. For example, the critical daylength for the common bean is shorter in the summer than in the winter. This means that common beans will flower sooner in the summer than in the winter. The photoperiod also affects the timing of flower development in plants that do not have a regular circadian rhythm. For example, the Venus flytrap (Dionaea muscipula) is a carnivorous plant that closes its trap-like leaves around insects. The Venus flytrap does not have a regular circadian rhythm, but it is sensitive to changes in the photoperiod. The Venus flytrap closes its leaves in response to changes in the daylength. When the days become shorter in the autumn, the Venus flytrap responds by closing its leaves and remaining dormant until the following spring. The photoperiod also affects the flowering time of many annual plants. Annual plants are plants that complete
The scientific method of describing a day or a 24-hour period is referred to as photographic time. This chart depicts the time that plants spend in daylight. It is known as a short day plant because it prefers less than 12 hours of sunlight per day to flower. Because of the Earth’s tilt and rotation, the daylight hours vary throughout the year. A petunia (Petunia spp.) bloom from May to early July, when it is most active. Tomato plants (Lycopers esciconulentum) fall into this category. Plants flower in any photoperiod and are considered day-neutral.
Daylength has a direct impact on plant dry weight and leaf area. LIW increased at a faster rate during the early stages of growth, reaching maximum values under the long daylength. The root percentage increased significantly in the beginning, as a result of a decrease in the percentage.
Because day length allows plants to adjust to different times of year rather than temperature, it is critical that they can adapt to different times of year rather than varying temperatures. A single species can coordinate its flowering and bloom at the same time, allowing all of its members to participate.
Short-day plants bloom when their nighttime lengths exceed the critical photoperiod of the plant.
As a result, long day plants are the correct answer.