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PLANT REPRODUCTIVE DEVELOPMENT (floral transition (factors influencing…

- - - - produce phytomers
      - indeterminate
    - - indeterminate
      - produce floral meristem
    - - determinate
      - produce floral organ
        
        stamens
        
        carpels
        
        petals
        
        sepals
      - identity genes
        
        LFY
        
        AP
  - - - by undergoing a sequence of
        
        physiological changes
        
        structural changes
    - - increased mitotic activity
      - changes in
        
        dimensions
        
        organization
- - - - sepal and petal
    - - petal and stamen
    - - stamen and pistil
    - - all above
- - - - interconvertible forms
        
        Pr
        
        absorbs photon of 660 nm light to convert to Pfr
        
        biologically inactive
        
        absorbs red light
        
        Pfr
        
        absorbs far red light
        
        absorbs photon of 730 nm light to convert to Pr
        
        biologically active
      - undergo photoconversation reactions
      - phytoreceptors
      - function as a biological switch, turning response on/off
    - - the process by which prolonged exposure to cold temperatures promotes folowering.
      - benefits/functions
        
        prevents premature reproductive development
        
        enables plants to have suffiecient maturity
      - rye varieties
        
        spring rye
        
        planted in spring
        
        flowers in summer
        
        summer rye
        
        planted in autumn
        
        germinates in winter
        
        flowers in summer
      - regulation by VRN genes
        
        VRN1
        
        induced by vernalization
        
        promotes the transition to reproductive development
        
        VRN2
        
        floral repressor
        
        integrates the
        
        vernalization
        
        day-length responses
        
        VRN + FT
        
        promote flowering
        
        FLORIGEN hypothesis
        
        FT/flowering locus t
        
        mRNA
        
        limiting factor for flowering
        
        hypothetical hormone
        
        not the final stimulus, induce another factor essential flowering
        
        movement
        
        1) loading
        
        FT translocate from companion cell ->sieve element
        
        2) transport
        
        long distance travel of FT through sieve elements
        
        3) unloading
        
        FT released from the apical end of the phloem
        
        4) cell-to-cell movement
        
        symplastic/apoplastic transport to the floral intial cluster
  - - - promote flowering
        
        application of exogenous GA
        
        studies on defective mutants in GA biosynthesis/signalling
      - GA pathway may acts in parallel to the day-length pathway
      - increases the transcriptional activity of the floral meristem activity