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How florigen,phtochromes and photoperiodism are linked? What is a Florigen? What is Photoperiodism?
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Solution
Florigen(or flowering hormone hormone-like molecule responsible for controlling and/or triggering flowering in plants.
Photoperiodismis the physiological reaction of organisms to the length of day or night. It occurs in plants. It turns out that this process is governed by a pigment, that is those
How does the plant "know" how long the day is? pigments which absorb light, The pigment involved in photoperiodism is known as a phytochrome.
(There are two forms of this pigment: Pr is the inactive form and Pfr is the active form. It is the Pfr form that triggers the plant response. When this Pfr form is present, it triggers flowering or triggers a seed to germinate. The absiccisic acid is responsible for dormant. One of the triggers that the seeds use to break dormancy is the amount of light that occurs in the spring as the light levels increase during the day. A flash of red light converts the inactive form, Pr, to the active form. Pfr. In those plants that were exposed to that flash of light during the dark period, that flash converted the inactive form to the active form. This signals to the short-day plants that there is too much light, so they will not flower. However, it signals to the long-day plants that there is enough light, so they flower even though the actual day length is too short to trigger that response. This response happens because the two forms of phytochrome respond to different wavelengths of red light. Pr is converted to Pfr by red light in the visible spectrum, about 660 nm. Under normal conditions with no flash of light during the dark period, the Pfr will gradually convert back to Pr. However, that flash during the night reconverts all of the Pr to Pfr, making the plant respond as if it were under long-day conditions. Pfr also can be converted to Pr by far-red light, about 730 nm, at the end of the visible spectrum.)
This finding was very exciting because it was the first time that we realized that a pigment can be used to control a plant's "behavior," the time at which it flowers. The plants are using pigments to sense environmental conditions, day length. Clearly then phytochromes are length of light period and dark period detectors. They directly govern Photoperiodism. Length of photoperiodism determines the amount of photosynthesis that takes place in a plant.
successful sexual reproduction of a plant with prolific seed production requires appropriate timing of flowering controlled by florigens and concomitant change of architecture (e.g. internode elongation and branching) to facilitate production of the optimal number of flowers while enabling continued resource production through photosynthesis. Photosysnthesis can only happen during light period. Hence photoperidism comes into the loop and phytochrome comes to play.
Florigen is the prime candidate for a signal linking the two processes. This is the link between florigen,phtochromes and photoperiodism
Photoperiodismis the physiological reaction of organisms to the length of day or night. It occurs in plants. It turns out that this process is governed by a pigment, that is those
How does the plant "know" how long the day is? pigments which absorb light, The pigment involved in photoperiodism is known as a phytochrome.
(There are two forms of this pigment: Pr is the inactive form and Pfr is the active form. It is the Pfr form that triggers the plant response. When this Pfr form is present, it triggers flowering or triggers a seed to germinate. The absiccisic acid is responsible for dormant. One of the triggers that the seeds use to break dormancy is the amount of light that occurs in the spring as the light levels increase during the day. A flash of red light converts the inactive form, Pr, to the active form. Pfr. In those plants that were exposed to that flash of light during the dark period, that flash converted the inactive form to the active form. This signals to the short-day plants that there is too much light, so they will not flower. However, it signals to the long-day plants that there is enough light, so they flower even though the actual day length is too short to trigger that response. This response happens because the two forms of phytochrome respond to different wavelengths of red light. Pr is converted to Pfr by red light in the visible spectrum, about 660 nm. Under normal conditions with no flash of light during the dark period, the Pfr will gradually convert back to Pr. However, that flash during the night reconverts all of the Pr to Pfr, making the plant respond as if it were under long-day conditions. Pfr also can be converted to Pr by far-red light, about 730 nm, at the end of the visible spectrum.)
This finding was very exciting because it was the first time that we realized that a pigment can be used to control a plant's "behavior," the time at which it flowers. The plants are using pigments to sense environmental conditions, day length.
Clearly then phytochromes are length of light period and dark period detectors. They directly govern Photoperiodism. Length of photoperiodism determines the amount of photosynthesis that takes place in a plant.
successful sexual reproduction of a plant with prolific seed production requires appropriate timing of flowering controlled by florigens and concomitant change of architecture (e.g. internode elongation and branching) to facilitate production of the optimal number of flowers while enabling continued resource production through photosynthesis. Photosysnthesis can only happen during light period. Hence photoperidism comes into the loop and phytochrome comes to play.
Florigen is the prime candidate for a signal linking the two processes. This is the link between florigen,phtochromes and photoperiodism
successful sexual reproduction of a plant with prolific seed production requires appropriate timing of flowering controlled by florigens and concomitant change of architecture (e.g. internode elongation and branching) to facilitate production of the optimal number of flowers while enabling continued resource production through photosynthesis. Photosysnthesis can only happen during light period. Hence photoperidism comes into the loop and phytochrome comes to play.
Florigen is the prime candidate for a signal linking the two processes. This is the link between florigen,phtochromes and photoperiodism
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