Floral induction, floral hormones and flowering

P.A. van de Pol

Research output: Thesisinternal PhD, WU


<p/>The factors, influencing the synthesis and action of floral hormones, and possible differences between floral hormones in different plants were studied. The experimental results are summarized in the conclusions 1-20, on pages 35-36 <em>(Crassulaceae');</em> 21-39 on pages 58-59 <em>('Xanthium strumarium')</em> and 40-50 on pages 74-75 <em>('Caryophyllaceae').</em><br/>General conclusions are as follows:<p/>1. The processes leading to flower formation of plants with a floral hormone can be roughly divided in induction and realization, the latter subdivided in synthesis, transport and action of floral hormone as initiation of flower buds in the receptive meristems. These processes are called the 'floral chain'.<p/>2. In the long-short-day plant <em>Bryophyllum daigremontianum</em> neither the LD, nor the SD induction were influenced qualitatively by temperature, but the resulting inductive state and the already synthesized floral hormone were destructed by too high a temperature.<p/>3. In the short-day plant <em>Kalanchoë blossfeldiana</em> the induction was influenced by temperature, so that in individual species different processes of the floral chain may be influenced.<p/>4. In the LSDP <em>B. daigremontianum</em> no 2 separate components of the floral hormone are formed.<p/>5. The transmission of floral hormone by grafting is influenced by the direction of movement of the hormone in <em>B. daigremontianum</em> and by the age of the receptor in the SDP <em>Xanthium strumarium.</em> Presence of the leaves in <em>X. strumarium</em> strongly stimulates the growth of the axillary shoots and reduces the flowering-reaction, while defoliation of receptors promotes the transmission of flowering.<p/>6. In <em>K. blossfeldiana</em> and <em>X.</em><em>strumarium</em> early lines need less floral hormone for a flowering-reaction than late ones. The former have a lower threshold value of the hormone.<p/>7. The good donor capacity of <em>B. daigremontianum</em> towards <em>K. blossfeldiana</em> in contrast to the reverse combination suggests a lower level of floral hormone in <em>K. blossfeldiana</em> than in <em>B. daigremontianum.</em><p/>8. Also in <em>X. strumarium</em> different levels of floral hormone, corresponding with different floral stages and different donor capacities, could be distinguished.<p/>9. The factors influencing the flowering of a receptor, grafted with a donor, mentioned sub 5, 6, 7 and 8, make it questionable to assume that plants without demonstrable transmission of flowering do not have a floral hormone, while negative results of interspecies graftings need not be caused by differences in floral hormones. New successful combinations between graft partners of different photoperiodic response types suggest a more universal floral hormone.<p/>10. The action of floral hormone is not restricted to floral initiation. In <em>K. blossfeldiana</em> the presence of sufficient floral hormone is also necessary for Rower development, while in <em>K.</em><em>blossfeldiana</em> and in <em>X. strumarium</em> the number of flowers depend on the level of floral hormone. In <em>B. daigremontianum</em> the presence of floral hormone is a condition for continued flowering.<p/>11. The term 'non-localized synthesis of floral hormone' was introduced for the phenomenon that receptors of some species brought into flowering by grafting, can act as a donor in a next grafting. It is likely that the difference between <em>B. daigremontianum</em> and <em>K.</em><em>blossfeldiana</em> concerning localized synthesis of floral hormone is caused by differences in internal conditions between these plants rather than by different floral hormones. Also the case of <em>Silene armeria,</em> brought into flowering by <em>Perilla crispa,</em> suggests this explanation.<p/>12. Since differences in flowering-reactions can be explained by different levels of floral hormone and/or by differences in internal conditions of the plants in which the floral hormone has to act, the existence of one universal floral hormone remains possible.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wellensiek, S.J., Promotor
Award date24 May 1972
Place of PublicationWageningen
Publication statusPublished - 1972


  • hormones
  • plant physiology
  • plant development
  • flowers
  • flowering
  • ornamental plants
  • plant growth regulators
  • fruits
  • plant organs


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