THE CONTROL OF FLOWERINGTHE CONTROL OF FLOWERING

PLANTS FLOWER AT DIFFERENT TIMES OF THE YEAR. PLANTS FLOWER AT DIFFERENT TIMES OF THE YEAR.

HOW DO PLANTS KEEP TRACK OF THE SEASONS?HOW DO PLANTS KEEP TRACK OF THE SEASONS?

WHICH ENVIRONMENTAL SIGNALS CONTROL WHICH ENVIRONMENTAL SIGNALS CONTROL FLOWERING?FLOWERING?

HOW DO ENVIRONMENTAL SIGNALS BRING ABOUT THE HOW DO ENVIRONMENTAL SIGNALS BRING ABOUT THE TRANSITION TO FLOWERING?TRANSITION TO FLOWERING?

FLOWERING IN FLOWERING IN ARABIDOPSISARABIDOPSIS

(B)

VEGETATIVE VS. FLOWERING SHOOT APEX IN VEGETATIVE VS. FLOWERING SHOOT APEX IN ARABIDOPSISARABIDOPSIS

VEGETATIVE APEX

FLOWERING APEX

FLORAL EVOCATIONFLORAL EVOCATION

THE EVENTS OCCURRING IN THE SHOOT APEX THE EVENTS OCCURRING IN THE SHOOT APEX THAT SPECIFICALLY COMMIT THE APICAL THAT SPECIFICALLY COMMIT THE APICAL MERISTEM TO PRODUCE FLOWERSMERISTEM TO PRODUCE FLOWERS

FLORAL ORGANS ARE INITITATED IN SUCCESSIVE FLORAL ORGANS ARE INITITATED IN SUCCESSIVE WHORLSWHORLS

MUTATIONS IN FLORAL ORGAN IDENTITY GENESMUTATIONS IN FLORAL ORGAN IDENTITY GENES

THE ABC MODEL FOR FLORAL ORGAN IDENTITYTHE ABC MODEL FOR FLORAL ORGAN IDENTITY

QUADRUPLE MUTANT (QUADRUPLE MUTANT (ap1, ap2, ap3/pi, agap1, ap2, ap3/pi, ag) RESULTS IN ) RESULTS IN THE PRODUCTION OF LEAF-LIKE STRUCTURES IN THE PRODUCTION OF LEAF-LIKE STRUCTURES IN

PLACE OF FLORAL ORGANSPLACE OF FLORAL ORGANS

THE SHOOT APEX AND PHASE CHANGESTHE SHOOT APEX AND PHASE CHANGES

THE SHOOT APICAL MERISTEM PASES THROUGH THREE DEVELOPMENTAL PHASES:

1. THE JUVENILE PHASE

2. THEADULT VEGETATIVE PHASE

3. THEADULT REPRODUCTIVE PHASE

JUVENILE AND ADULT FORMS OF ENGLISH IVY (JUVENILE AND ADULT FORMS OF ENGLISH IVY (Hedera Hedera helixhelix))

ADULTJUVENILE

(GIBBERELLIN CAUSES REVERSION OF ADULT FORM TO JUVENILE FORM IN ENGLISH IVY)

FLORAL EVOCATION: COMPETENCE AND FLORAL EVOCATION: COMPETENCE AND DETERMINATIONDETERMINATION

PHOTOPERIODISM: MONITORING DAY PHOTOPERIODISM: MONITORING DAY LENGTHLENGTH

PLANTS CAN USE CIRCADIAN RHYTHMS TO PLANTS CAN USE CIRCADIAN RHYTHMS TO MEASURE DAYLENGTHMEASURE DAYLENGTH

PLANTS CAN USE CIRCADIAN RHYTHMS TO MEASURE PLANTS CAN USE CIRCADIAN RHYTHMS TO MEASURE TIMETIME

Entrained rhythm Free running rhythm

DAY LENGTH VARIES WITH LATTITUDEDAY LENGTH VARIES WITH LATTITUDE

DAY LENGTH VARIES WITH THE MONTH OF THE YEAR DAY LENGTH VARIES WITH THE MONTH OF THE YEAR AND THE LATTITUDE, EXCEPT AT THE EQUATORAND THE LATTITUDE, EXCEPT AT THE EQUATOR

Day length = night length all year at the equator

THE DISCOVERY OF PHOTOPERIODISMTHE DISCOVERY OF PHOTOPERIODISM

1.1. GARNER AND ALLARD (1920s) AT USDA LAB GARNER AND ALLARD (1920s) AT USDA LAB AT BELTSVILLE, MD STUDIED FLOWERING IN AT BELTSVILLE, MD STUDIED FLOWERING IN MARYLAND MAMMOTH TOBACCO PLANT.MARYLAND MAMMOTH TOBACCO PLANT.

2.2. MARYLAND MAMMOTH WAS A SINGLE GENE MARYLAND MAMMOTH WAS A SINGLE GENE MUTANT TOBACCO THAT DIDN’T FLOWER IN MUTANT TOBACCO THAT DIDN’T FLOWER IN THE SPRING OR SUMMER, LIKE WILD TYPE.THE SPRING OR SUMMER, LIKE WILD TYPE.

3.3. IT ONLY FLOWERED WHEN BROUGHT INTO IT ONLY FLOWERED WHEN BROUGHT INTO THE GREEN HOUSE IN THE WINTER.THE GREEN HOUSE IN THE WINTER.

PLANTS CAN BE CLASSIFIED ACCORDING TO THEIR PLANTS CAN BE CLASSIFIED ACCORDING TO THEIR PHOTOPERIODIC RESPONSESPHOTOPERIODIC RESPONSES

1.1. Short Day Plants (SDPs) flower when day length is Short Day Plants (SDPs) flower when day length is shorter than a critical day length.shorter than a critical day length.

2.2. Long day plants (LDPs) flower when the day length is Long day plants (LDPs) flower when the day length is longer than a critical daylength.longer than a critical daylength.

3.3. Long-short-day plants (LSDPs) flower after a Long-short-day plants (LSDPs) flower after a sequence of long days followed by short days.sequence of long days followed by short days.

4.4. Short-long-day plants (SLDPs) flower after a Short-long-day plants (SLDPs) flower after a sequence of short days followed by long days.sequence of short days followed by long days.

5.5. Day-neutral plants (DNPs) are insensitive to Day-neutral plants (DNPs) are insensitive to daylength, Flowering is under internal developmental daylength, Flowering is under internal developmental control.control.

THE SITE OF PERCEPTION OF THE THE SITE OF PERCEPTION OF THE PHOTOPERIODIC STIMULUS IS THE PHOTOPERIODIC STIMULUS IS THE

LEAFLEAF

EFFECT OF DAY LENGTH ON FLOWERING IN SDPs AND EFFECT OF DAY LENGTH ON FLOWERING IN SDPs AND LDPsLDPs

Critical day langth Critical day langth

NIGHT BREAK EXPERIMENTS DEMONSTRATE ROLE OF NIGHT BREAK EXPERIMENTS DEMONSTRATE ROLE OF NIGHT PERIOD IN SDPsNIGHT PERIOD IN SDPs

NIGHT BREAK EXPERIMENTS ALSO DEMONSTRATE NIGHT BREAK EXPERIMENTS ALSO DEMONSTRATE ROLE OF NIGHT PERIOD IN LDPsROLE OF NIGHT PERIOD IN LDPs

THE LENGTH OF THE DARK PERIOD REGULATES THE THE LENGTH OF THE DARK PERIOD REGULATES THE PHOTOPERIODIC RESPONSES IN BOTH SDPs AND LDPsPHOTOPERIODIC RESPONSES IN BOTH SDPs AND LDPs

NIGHT BREAKS GIVEN AT DIFFERENT TIMES DURING NIGHT BREAKS GIVEN AT DIFFERENT TIMES DURING THE NIGHT PERIOD REVEAL CIRCADIAN RHYTHMICITYTHE NIGHT PERIOD REVEAL CIRCADIAN RHYTHMICITY

ACCORDING TO THE COINCIDENCE MODEL, THE ACCORDING TO THE COINCIDENCE MODEL, THE EFFECT OF THE NIGHT BREAK DEPENDS ON THE EFFECT OF THE NIGHT BREAK DEPENDS ON THE

RHYTHM OF LIGHT SENSITIVITYRHYTHM OF LIGHT SENSITIVITY

(SDP Soybean)

PHYTOCHROME IS THE PIGMENT INVOLVED IN PHYTOCHROME IS THE PIGMENT INVOLVED IN MEASURING THE NIGHT LENGTHMEASURING THE NIGHT LENGTH

AS IN THE CASE OF SDPs, ACCORDING TO THE AS IN THE CASE OF SDPs, ACCORDING TO THE COINCIDENCE MODEL, THE EFFECT OF THE NIGHT COINCIDENCE MODEL, THE EFFECT OF THE NIGHT

BREAK DEPENDS ON THE RHYTHM OF LIGHT BREAK DEPENDS ON THE RHYTHM OF LIGHT SENSITIVITYSENSITIVITY

LDP Arabidopsis

VERNALIZATION: PROMOTING FLOWERING WITH COLD VERNALIZATION: PROMOTING FLOWERING WITH COLD TREATMENT (40 DAYS AT 4TREATMENT (40 DAYS AT 4C)C)

Winter-annual Arabidopsis without vernalization

Winter-annual Arabidopsis with vernalization

VERNALIZATION: SITE OF PERCEPTIONVERNALIZATION: SITE OF PERCEPTION

THE SITE OF PERCEPTION OF THE SITE OF PERCEPTION OF

VERNALIZATION IS THE VERNALIZATION IS THE SHOOT TIPSHOOT TIP

DEVERNALIZATIONDEVERNALIZATION

THE EFFECT OF COLD TEMPERATURE IN THE EFFECT OF COLD TEMPERATURE IN PROMOTING FLOWERING CAN BE REVERSED PROMOTING FLOWERING CAN BE REVERSED BY WARM TEMPERATURE (DEVERNALIZATION)BY WARM TEMPERATURE (DEVERNALIZATION)

VERNALIZATION BLOCKS THE EXPRESSION OF THE VERNALIZATION BLOCKS THE EXPRESSION OF THE GENE GENE FLOWERING LOCUS CFLOWERING LOCUS C ( (FLC)FLC)

Winter annual after 40 cold days

Winter annual without cold

Winter annual without cold, but with FLC mutation

FLC mRNA

GRAFTING STUDIESGRAFTING STUDIES

GRAFTING STUDIES HAVEGRAFTING STUDIES HAVE

DEMONSTRATED THE ROLE OF A DEMONSTRATED THE ROLE OF A

TRANSMISSIBLE STIMULUS PRODUCED BY TRANSMISSIBLE STIMULUS PRODUCED BY

LEAVES WHEN PHOTOPERIODICALLY LEAVES WHEN PHOTOPERIODICALLY

INDUCED.INDUCED.

DEMONSTRATION OF LEAF-GENERATED FLORAL DEMONSTRATION OF LEAF-GENERATED FLORAL STIMULUS (FLORIGEN) IN THE SDP STIMULUS (FLORIGEN) IN THE SDP PERILLAPERILLA

Induced graft donor leaf

Uninduced graft donor leaf

SUCCESSFUL TRANSMISSION OF FLORAL STIMULUS SUCCESSFUL TRANSMISSION OF FLORAL STIMULUS BY INTERGENERIC GRAFTING BY INTERGENERIC GRAFTING

Scion: LDP Petunia hybrida, induced with long days.

Stock: Nonvernalized, cold-requiring LDP Hyascyamus niger (henbane)

THE PHENOMENON OF INDIRECT INDUCTIONTHE PHENOMENON OF INDIRECT INDUCTION

MULTIPLE INDUCTION BY A SINGLE INDUCED LEAFMULTIPLE INDUCTION BY A SINGLE INDUCED LEAF