Articles
THE FLOWERING PROCESS AND ITS CONTROL
G. Bernier (Université de Liège, Belgium) at the symposium "Flowering and Fruit Set in Fruit Trees". Dr.
Bernier was asked to give a summary of the basic work done in his laboratory on the flowering of an herbaceous plant (Sinapis alba L.) in which the sequence of events transforming the vegetative meristem into a reproductive one is particularly well known and described (Bernier et al., 1981). When asking this task to my colleague and friend Bernier, I wished that people involved in applied research on fruit trees realize that basic research on flowering was going on with success and that some lessons could be taken from this contribution in order to better understand and generalize the results obtained on fruit trees.
From the beginning, Dr.
Bernier did not intend to publish his paper which should not contain new results but only a summary of data published elsewhere.
From the beginning also, I wished to get the opportunity of including in the proceedings a personal assessment of some of the discussion sessions organized during the meeting.
Finally, in agreement with Dr.
Bernier, I decided to write this report of the inaugural address as well as an assessment of the discussion sessions on the flowering process.
Anyone interested in flowering will find a much more complete report of the ideas developed in this inaugural address in a paper which should be published by Bernier (1983).
The first important idea of Bernier was that it seemed that no basic difference should exist between herbaceous and woody plants as far as the control of flower initiation is concerned.
It is even possible that the sequence of changes at the meristem level could be the same in both types of plants.
The mechanisms avoiding the flowering of some buds but not in others are obviously more developed in fruit trees.
It is also well known by orchardists that the external factors of the environment and the cultural practices are important determinants of flowering in perennial woody plants.
According to Bernier, the differences between both types of plants are only quantitative.
Three steps have to be considered in the study of the flowering process:
- induction: the changes occuring in the leaves and resulting in the production of a "floral stimulus";
- translocation of the "floral stimulus" out of the leaves towards the meristems (terminal and/or axillary) where flowering will take place;
- evocation followed by the floral morphogenesis : the changes occuring at the meristem level for transforming a vegetative meristem into a reproductive one.