The period of daylight, specific in length for any given species, that appears to initiate flowering in *long-day plants or inhibit flowering in *short-day plants. In actual fact long-day plants will not flower if the dark period exceeds a certain maximum and conversely short-day plants will not flower unless the dark period exceeds a certain minimum. These periods are termed critical dark periods and must be continuous to have effect (see night-break effect ).
Short day plants require a period of darkness longer than a critical length to flower, while long day plants require a period of darkness shorter than a critical length to flower.
Photoperiodism is the response of the plant to daylight and darkness. For short day plants it will bloom in darkness and when darkness exceeds critical night length, for long day plants it will bloom during daylight and when darkness is less than the critical night length.
Long day plants require a certain minimum amount of daylight to flower, while short day plants need a specific maximum amount of daylight. Long day plants flower when days are longer than a critical length, while short day plants flower when days are shorter than a critical length. The growth patterns of these plants vary based on the length of daylight they receive, with long day plants flowering in the summer when days are longer, and short day plants flowering in the fall when days are shorter.
In long day plants, flowering is initiated by exposure to a certain amount of light during a 24-hour period. When the length of daylight exceeds a critical threshold, it triggers the production of flowering hormones that stimulate the plant to transition from vegetative growth to the reproductive phase.
Mars.
the length of day on earth is 24 hours
Mars
The length of the day in th US is the same as the length of the day anywhere else in the world, roughly 24 hours.
the length of a day on Jupiter is average, 9.9 hours
the length of the day is not a fixed unit of time
See answer given for length of Venus day in hours.
The length of a "day" on the moon is 29 Earth days.