Guest edited by D. A. DeMason and A. M. Hirsch
Do Fibonacci numbers reveal the involvement of geometrical imperatives or biological interactions in phyllotaxis?
Article first published online: 17 JAN 2006
Botanical Journal of the Linnean Society
Volume 150, Issue 1, pages 3–24, January 2006
How to Cite
COOKE, T. J. (2006), Do Fibonacci numbers reveal the involvement of geometrical imperatives or biological interactions in phyllotaxis?. Botanical Journal of the Linnean Society, 150: 3–24. doi: 10.1111/j.1095-8339.2006.00490.x
- Issue published online: 17 JAN 2006
- Article first published online: 17 JAN 2006
- Received December 2004; accepted for publication April 2005
- golden ratio;
- number sequence;
- optimal packing;
- spiral phyllotaxis;
- whorled phyllotaxis
Complex biological patterns are often governed by simple mathematical rules. A favourite botanical example is the apparent relationship between phyllotaxis (i.e. the arrangements of leaf homologues such as foliage leaves and floral organs on shoot axes) and the intriguing Fibonacci number sequence (1, 2, 3, 5, 8, 13 . . .). It is frequently alleged that leaf primordia adopt Fibonacci-related patterns in response to a universal geometrical imperative for optimal packing that is supposedly inherent in most animate and inanimate structures. This paper reviews the fundamental properties of number sequences, and discusses the under-appreciated limitations of the Fibonacci sequence for describing phyllotactic patterns. The evidence presented here shows that phyllotactic whorls of leaf homologues are not positioned in Fibonacci patterns. Insofar as developmental transitions in spiral phyllotaxis follow discernible Fibonacci formulae, phyllotactic spirals are therefore interpreted as being arranged in genuine Fibonacci patterns. Nonetheless, a simple modelling exercise argues that the most common spiral phyllotaxes do not exhibit optimal packing. Instead, the consensus starting to emerge from different subdisciplines in the phyllotaxis literature supports the alternative perspective that phyllotactic patterns arise from local inhibitory interactions among the existing primordia already positioned at the shoot apex, as opposed to the imposition of a global imperative of optimal packing. © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society, 2006, 150, 3–24.