Phytochrome Lecture

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



Long-Day Plants Need Low Pr!

(Fast)

Dark Reversion

Red Light740 nm660 nm

PrPrFar Red Light

PfrPfr

(Slow)


Vegetative(Non-Flowering)


Long Night


Sunset orFar Red Light

660 nm 740 nmRed Light

(Fast)

Dark Reversion

PrPrFar Red Light





Mid-Summer Sunlight660 nm 740 nm

Red Light(Fast)

Dark Reversion

PrPrFar Red Light




(Slow)

Short-Day Plant Need Low Pfr!

Winter Far Red Light

(Fast)

Dark Reversion

Red Light

660 nm

PrPrFar Red Light

740 nm




(Slow)

Short-Day Plant Need Low Pfr!

LongNight

660 nm 740 nmRed Light

(Fast)

Dark Reversion

PrPrFar Red Light


(Slow) Vegetative(Non-Flowering)


Short-Day Plants Need Low Pfr!

(Fast)

Dark Reversion

Red Light740 nm660 nm

PrPrFar Red Light

PfrPfr

(Slow)




Black Cloth

Short-Day Plants Need Low Pfr!

Night Break

(Fast)

Dark Reversion

Red Light740 nm

660 nm

PrPr PfrPfrFar Red Light


(Slow) Vegetative(Non-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?

Phytochrome Lecture

Documents

Transcript of Phytochrome Lecture