The Pigment That Controls Growth and Flowering In Many Plants.

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 The actual plant response is very specific to each specie, and some specific to each specie, and some plants do not respond at all. plants do not respond at all.

Which Wavelengths Are Photoperiodic?

The length of the night period plays a major role in determining which 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 Thus the length of exposure to light in a building, or if outdoors, the seasonal light building, or if outdoors, the seasonal light changes, affect how long the plants perceives changes, affect how long the plants perceives each form of phytochrome. each form of phytochrome.

R FR

Photoperiodic Response:

It’s all about Preferences!

Long Day Plants flower when there is adequate PR

Short Day Plants flower when there is adequate Pfr

(Fast)

Dark Reversion

Red Light

740 nm660 nm

PrPr PfrPfr

(Slow)

Far Red Light

Synthesis Destruction

Vegetative(Non-Flowering)

Reproductive(Flowering)

(Fast)

Dark Reversion

Red Light

740 nm660 nm

PrPr PfrPfr

(Slow)

Far Red LightSynthesis Destruction



Mid-Summer Sunlight

Long-Day Plants Need Low Pr!

(Fast)

Dark Reversion

Red Light

740 nm660 nm

PrPr PfrPfr

(Slow)




Long Night


(Fast)

Dark Reversion

Red Light

740 nm660 nm

PrPr PfrPfr

(Slow)




Sunset orFar Red Light


(Fast)

Dark Reversion

Red Light

740 nm660 nm

PrPr PfrPfr

(Slow)




Mid-Summer Sunlight

Short-Day Plant Need Low Pfr!

(Fast)

Dark Reversion

Red Light

740 nm660 nm

PrPr PfrPfr

(Slow)




Short-Day Plant Need Low Pfr!

Winter Far Red

Light

(Fast)

Dark Reversion

Red Light

740 nm660 nm

PrPr PfrPfr

(Slow)




LongNight

Short-Day Plants Need Low Pfr!

(Fast)

Dark Reversion

Red Light

740 nm660 nm

PrPr PfrPfr

(Slow)




Black Cloth

Short-Day Plants Need Low Pfr!

(Fast)

Dark Reversion

Red Light

740 nm660 nm

PrPr PfrPfr

(Slow)




Night Break

Night lighting disrupts reversion to Prand maintains vegetative status!

Photoperiod type

Short-Day(Long-Night)Long -Day(Short-Night)

Continuous long, dark period

Continuous short, dark period

Interrupted dark period

24-hour day cycle

Critical day length

Light Interruption of Darkness Affects Short- and Long-Day

Plants Differently

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.

SUPPLEMENTAL LIGHTING

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

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.

DAILY DURATION OF LIGHT

The Pigment That Controls Growth and Flowering In Many Plants.

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