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Phytochrome Lecture
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The Pigment That Controls Growth and Flowering In Many
Plants
What Is Phytochrome ?
Phytochrome is a pigment found in some plant cells that has been proven to control plant development.
This pigment has two forms or phases in can exist in. P-red light sensitive (Pr) and P far red light sensitive (Pfr) forms.
The actual plant response is very specific to each The actual plant response is very specific to each specie, and some plants do not respond at all. specie, and some plants do not respond at all.
Which Wavelengths Are Photoperiodic?
The length of the night period plays a major role in determiningwhich wavelength will be effective, as the phytochrome pigment tends to revert to Pr during long periods of darkness.
Thus the length of exposure to light in a building, or if outdoThus the length of exposure to light in a building, or if outdoors, ors, the seasonal light changes, affect how long the plants perceivesthe seasonal light changes, affect how long the plants perceiveseach form of each form of phytochromephytochrome. . R FR
Photoperiodic Response:
Its all about Preferences!
Long Day Plants flower when there is adequate PR
Short Day Plants flower when there is adequate Pfr
660 nm
PrPrFar Red Light
Synthesis Destruction
740 nmRed Light
PfrPfr(Fast)
Dark Reversion
(Slow)Vegetative(Non-Flowering)
Reproductive(Flowering)
Mid-Summer Sunlight
660 nm740 nm
Red Light(Fast)
Dark Reversion
PrPrFar Red Light
PfrPfrSynthesis Destruction
(Slow)Vegetative(Non-Flowering)
Reproductive(Flowering)
Long-Day Plants Need Low Pr!
(Fast)
Dark Reversion
Red Light740 nm660 nm
PrPrFar Red Light
PfrPfr
(Slow)
Synthesis Destruction
Vegetative(Non-Flowering)
Reproductive(Flowering)
Long Night
Long-Day Plants Need Low Pr!
Sunset orFar Red Light
660 nm 740 nmRed Light
(Fast)
Dark Reversion
PrPrFar Red Light
PfrPfrSynthesis Destruction
(Slow)Vegetative(Non-Flowering)
Reproductive(Flowering)
Long-Day Plants Need Low Pr!
Mid-Summer Sunlight660 nm 740 nm
Red Light(Fast)
Dark Reversion
PrPrFar Red Light
PfrPfrSynthesis Destruction
Reproductive(Flowering)
Vegetative(Non-Flowering)
(Slow)
Short-Day Plant Need Low Pfr!
Winter Far Red Light
(Fast)
Dark Reversion
Red Light
660 nm
PrPrFar Red Light
740 nm
PfrPfrSynthesis Destruction
Reproductive(Flowering)
Vegetative(Non-Flowering)
(Slow)
Short-Day Plant Need Low Pfr!
LongNight
660 nm 740 nmRed Light
(Fast)
Dark Reversion
PrPrFar Red Light
PfrPfrSynthesis Destruction
(Slow) Vegetative(Non-Flowering)
Reproductive(Flowering)
Short-Day Plants Need Low Pfr!
(Fast)
Dark Reversion
Red Light740 nm660 nm
PrPrFar Red Light
PfrPfr
(Slow)
Synthesis Destruction
Vegetative(Non-Flowering)
Reproductive(Flowering)
Black Cloth
Short-Day Plants Need Low Pfr!
Night Break
(Fast)
Dark Reversion
Red Light740 nm
660 nm
PrPr PfrPfrFar Red Light
Synthesis Destruction
(Slow) Vegetative(Non-Flowering)
Reproductive(Flowering)
Night lighting disrupts reversion to Prand maintains vegetative status!
Light Interruption of Darkness Affects Short- and Long-Day Plants Differently
Photoperiod type
Short-Day(Long-Night)
Long -Day(Short-Night)
Continuous short, dark period
Continuous long, dark period
Interrupted dark period
24-hour day cycle Critical day length
Questions?
The Phytochrome System Works Within The Apical Meristem
Photoperiodicresponses are triggered in the meristem (both apical and axillary), long before the new branches develop.
We can control development !
To lengthen the night, plants are covered with a blackout shade cloth. Applied in late afternoon and removed in the morning (5 pm to 8 am)
Photoperiodic shade cloth
Light penetration through the shade cloth should not be more than 2 fc in order to prevent delay in flowering and/or disfigured flowers.
SUPPLEMENTALLIGHTING
Light sources. incandescent lamps emit large amounts of red light and are good for lighting mums (standard mum lighting) mums flower when the day length decreases to 13.5 hrs or less whenever the day length is longer than 14.5 hrs plants remain vegetative split each long night in two short nights with supplemental light to prevent flowering
DAILY DURATION OF LIGHT
The length of day has an effect on two plant processes time of flowering plant maturity
This light-induced response is called photoperiodism, and plants that flower under only certain day-length conditions are called photoperiodic.
The Pigment That Controls Growth and Flowering In Many PlantsQuestions?