1. Types of Plant photoperiod response
Plants can be divided into long-day plants (long-day plant, abbreviated as LDP), short-day plants (short-day plant, abbreviated as SDP), and day-neutral plants (day-neutral plant, abbreviated as DNP) according to the type of response to the length of sunlight during a certain period of development.
LDP refers to plants that must be longer than a certain number of hours of light per day and can pass a certain number of days before they can bloom. Such as winter wheat, barley, rapeseed, Semen Hyoscyami, sweet olive and beet, etc., and the longer the light time, the earlier the flowering.
SDP refers to plants that must be less than a certain number of hours of light per day before they can bloom. If the light is appropriately shortened, flowering can be advanced in advance, but if the light is extended, flowering can be delayed or not flowering. Such as rice, cotton, soybean, tobacco, begonia, chrysanthemum, morning glory and cocklebur and so on.
DNP refers to plants that can bloom under any sunlight conditions, such as tomatoes, cucumbers, rose, and clivia and so on.
2. Key Issues in the Application of Plant Flowering Photoperiod Regulation
Plant critical day length
The critical day length refers to the longest daylight that can be tolerated by a short-day plant during the day-night cycle or the shortest daylight that is necessary to induce a long-day plant to flower. For LDP, the day length is greater than the critical day length, and even 24 hours can bloom. However, for SDP, the day length must be less than the critical day length to flower, but too short to flower.
Key of plant flowering and artificial control of photoperiod
SDP flowering is determined by the length of the dark period and does not depend on the length of light. The length of sunshine required for LDP to bloom is not necessarily longer than the length of sunshine required for SDP to bloom.
Understanding the key types of plant flowering and photoperiod response can extend or shorten the length of sunlight in the greenhouse, control the flowering period, and solve the problem of flowering. Using Growook’s LED Growpower Controller to extend the light can accelerate the flowering of long-day plants, effectively shorten the light, and promote the flowering of short-day plants early. If you want to delay flowering or not flowering, you can reverse the operation. If long-day plants are cultivated in the tropics, they will not bloom because of insufficient light. Similarly, short-day plants will be cultivated in temperate and cold zones because they will not bloom for too long.
3. Introduction and breeding work
The artificial control of plant photoperiod is of great significance to plant introduction and breeding. Growook takes you to know more about the characteristics of plants lighting. For LDP, seeds from the north are introduced to the south, and early-maturing varieties is required to delay flowering. The same goes for the south species to the north, which requires late-maturing varieties.
4. Flower induction by Pr and Pfr
Photosensitizers mainly receive Pr and Pfr signals, which affect the induction of flower formation in plants. The flowering effect is not determined by the absolute amounts of Pr and Pfr, but by the Pfr / Pr ratio. SDP produces flowers at a lower Pfr / Pr ratio, while formation of LDP flower-forming stimuli requires a relatively high Pfr / Pr ratio. If the dark period is interrupted by red light, the ratio of Pfr / Pr will increase, and SDP flower formation will be suppressed. The requirements of LDP on the ratio of Pfr / Pr are not as strict as those of SDP, but long enough light time, relatively high irradiance, and far-red light are necessary to induce LDP to flower.