Séminaires MSC
"Matière et Systèmes Complexes"

Lundi 13 septembre 2010 à 11h30
Bâtiment Condorcet, 3ème étage, salle 366 A.

Siobhan Braybrook
(Institute of Plant Sciences, Bern)

The striking pattern seen in the sunflower (Helianthus annuus) floral head is a famous example of the Fibonacci series.  When you observe an adult sunflower head, what you see is not a single flower but instead many small flowers.  The central flowers are organized such that your eye can easily discern spiral paristiches, both clockwise and counter-clockwise.  When counted in each direction, these spirals almost always exhibit numbers of the Fibonacci sequence.  This pattern has fascinated biologists, mathematicians, and physicists for hundreds of years.

I am examining how the information for this pattern is transmitted in both space (the growing sunflower tissue) and in time (through the life of the plant).
Using micro-surgical techniques and biochemical manipulation I have inferred interesting properties about the establishment and maintenance of this pattern: The Fibonacci spirals seen with the eye are an emergent property that results from a local organizing rule, and a pattern 'history' in time.