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THE CONTROL OF FLOWERING

THE CONTROL OF FLOWERING. HOW DO PLANTS KEEP TRACK OF THE SEASONS?. PLANTS FLOWER AT DIFFERENT TIMES OF THE YEAR. WHICH ENVIRONMENTAL SIGNALS CONTROL FLOWERING?. HOW DO ENVIRONMENTAL SIGNALS BRING ABOUT THE TRANSITION TO FLOWERING?. FLOWERING IN ARABIDOPSIS. (B).

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THE CONTROL OF FLOWERING

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  1. THE CONTROL OF FLOWERING HOW DO PLANTS KEEP TRACK OF THE SEASONS? • PLANTS FLOWER AT DIFFERENT TIMES OF THE YEAR. WHICH ENVIRONMENTAL SIGNALS CONTROL FLOWERING? HOW DO ENVIRONMENTAL SIGNALS BRING ABOUT THE TRANSITION TO FLOWERING?

  2. FLOWERING IN ARABIDOPSIS (B)

  3. VEGETATIVE VS. FLOWERING SHOOT APEX IN ARABIDOPSIS VEGETATIVE APEX FLOWERING APEX

  4. FLORAL EVOCATION • THE EVENTS OCCURRING IN THE SHOOT APEX THAT SPECIFICALLY COMMIT THE APICAL MERISTEM TO PRODUCE FLOWERS

  5. FLORAL ORGANS ARE INITITATED IN SUCCESSIVE WHORLS

  6. MUTATIONS IN FLORAL ORGAN IDENTITY GENES

  7. THE ABC MODEL FOR FLORAL ORGAN IDENTITY

  8. QUADRUPLE MUTANT (ap1, ap2, ap3/pi, ag) RESULTS IN THE PRODUCTION OF LEAF-LIKE STRUCTURES IN PLACE OF FLORAL ORGANS

  9. THE 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

  10. JUVENILE AND ADULT FORMS OF ENGLISH IVY (Hedera helix) JUVENILE ADULT (GIBBERELLIN CAUSES REVERSION OF ADULT FORM TO JUVENILE FORM IN ENGLISH IVY)

  11. FLORAL EVOCATION: COMPETENCE AND DETERMINATION

  12. PHOTOPERIODISM: MONITORING DAY LENGTH • PLANTS CAN USE CIRCADIAN RHYTHMS TO MEASURE DAYLENGTH

  13. PLANTS CAN USE CIRCADIAN RHYTHMS TO MEASURE TIME Entrained rhythm Free running rhythm

  14. DAY LENGTH VARIES WITH LATTITUDE

  15. DAY LENGTH VARIES WITH THE MONTH OF THE YEAR AND THE LATTITUDE, EXCEPT AT THE EQUATOR Day length = night length all year at the equator

  16. THE DISCOVERY OF PHOTOPERIODISM • GARNER AND ALLARD (1920s) AT USDA LAB AT BELTSVILLE, MD STUDIED FLOWERING IN MARYLAND MAMMOTH TOBACCO PLANT. • MARYLAND MAMMOTH WAS A SINGLE GENE MUTANT TOBACCO THAT DIDN’T FLOWER IN THE SPRING OR SUMMER, LIKE WILD TYPE. • IT ONLY FLOWERED WHEN BROUGHT INTO THE GREEN HOUSE IN THE WINTER.

  17. PLANTS CAN BE CLASSIFIED ACCORDING TO THEIR PHOTOPERIODIC RESPONSES • Short Day Plants (SDPs) flower when day length is shorter than a critical day length. • Long day plants (LDPs) flower when the day length is longer than a critical daylength. • Long-short-day plants (LSDPs) flower after a sequence of long days followed by short days. • Short-long-day plants (SLDPs) flower after a sequence of short days followed by long days. • Day-neutral plants (DNPs) are insensitive to daylength, Flowering is under internal developmental control.

  18. THE SITE OF PERCEPTION OF THE PHOTOPERIODIC STIMULUS IS THE LEAF

  19. EFFECT OF DAY LENGTH ON FLOWERING IN SDPs AND LDPs Critical day langth Critical day langth

  20. NIGHT BREAK EXPERIMENTS DEMONSTRATE ROLE OF NIGHT PERIOD IN SDPs

  21. NIGHT BREAK EXPERIMENTS ALSO DEMONSTRATE ROLE OF NIGHT PERIOD IN LDPs

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

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

  24. ACCORDING TO THE COINCIDENCE MODEL, THE EFFECT OF THE NIGHT BREAK DEPENDS ON THE RHYTHM OF LIGHT SENSITIVITY (SDP Soybean)

  25. PHYTOCHROME IS THE PIGMENT INVOLVED IN MEASURING THE NIGHT LENGTH

  26. AS IN THE CASE OF SDPs, ACCORDING TO THE COINCIDENCE MODEL, THE EFFECT OF THE NIGHT BREAK DEPENDS ON THE RHYTHM OF LIGHT SENSITIVITY LDP Arabidopsis

  27. VERNALIZATION: PROMOTING FLOWERING WITH COLD TREATMENT (40 DAYS AT 4C) Winter-annual Arabidopsiswith vernalization Winter-annual Arabidopsis without vernalization

  28. VERNALIZATION: SITE OF PERCEPTION • THE SITE OF PERCEPTION OF • VERNALIZATION IS THE SHOOT TIP

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

  30. VERNALIZATION BLOCKS THE EXPRESSION OF THE GENE FLOWERING LOCUS C (FLC) Winter annual without cold Winter annual without cold, but with FLC mutation Winter annual after 40 cold days FLC mRNA

  31. GRAFTING STUDIES GRAFTING STUDIES HAVE DEMONSTRATED THE ROLE OF A TRANSMISSIBLE STIMULUS PRODUCED BY LEAVES WHEN PHOTOPERIODICALLY INDUCED.

  32. DEMONSTRATION OF LEAF-GENERATED FLORAL STIMULUS (FLORIGEN) IN THE SDP PERILLA Induced graft donor leaf Uninduced graft donor leaf

  33. SUCCESSFUL TRANSMISSION OF FLORAL STIMULUS BY INTERGENERIC GRAFTING Scion: LDP Petunia hybrida, induced with long days. Stock: Nonvernalized, cold-requiring LDP Hyascyamus niger (henbane)

  34. THE PHENOMENON OF INDIRECT INDUCTION

  35. MULTIPLE INDUCTION BY A SINGLE INDUCED LEAF

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