Define a) short day and b) long day plant using the plant's ability to measure the length of the dark period.
a) Short day plant: A short day plant is a type of plant that requires a longer period of darkness (usually more than 12 hours) in a 24-hour cycle in order to trigger the processes of flowering, fruiting, or other key developmental stages. These plants have a critical photoperiod, during which the length of darkness must exceed a specific threshold to induce flowering. If the length of darkness falls below this critical threshold, the plant's physiological response will be delayed or inhibited.
b) Long day plant: A long day plant is a type of plant that requires a shorter period of darkness (usually less than 12 hours) in a 24-hour cycle to initiate flowering, fruiting, or other crucial developmental events. These plants have a critical photoperiod, during which the length of darkness must be lower than a specific threshold to trigger flowering. If the duration of darkness exceeds this critical threshold, the plant's physiological response will be delayed or suppressed.
a) Short-day plant:
A short-day plant, also known as a long-night plant or a long-day repressor, is a type of plant that requires a relatively long period of darkness (usually more than 12 hours) to initiate flowering. The length of the dark period, rather than the light period, is critical for the growth and development of these plants. Examples of short-day plants include poinsettias, chrysanthemums, and soybeans.
b) Long-day plant:
On the other hand, a long-day plant, also known as a short-night plant or a long-day promoter, is a plant that requires a shorter period of darkness (usually less than 12 hours) to trigger the flowering process. These plants typically need a longer duration of light exposure to initiate flowering, rather than a prolonged dark period. Examples of long-day plants include radishes, lettuce, and spinach.
In summary, the classification of short-day and long-day plants is based on the plant's response to the length of the dark period. Short-day plants require a longer dark period to flower, while long-day plants need a shorter dark period to initiate flowering.