Botanical Glossary

Fibonacci Phyllotaxis

Definition: A fundamental type of leaf arrangement expressed as a fraction in which each succeeding fraction is the sum of the two previous numerators and the sum of the two previous denominators, i.e., 1/2, 1/3, 2/5, 3/8, 5/13, 8/ 21, etc. The numerator represents the number of turns or spirals around a stem before one leaf is directly above another and the denominator represents the number of leaves in the turns or spirals before one is directly above the other. 2/5 phyllotaxy would mean two twists and five leaves before one leaf is directly above the other or an angle of divergence of 144 between succeeding leaves in the stem (2/5 of 360 ).According to Leppik anthotaxis and semataxis do not necessarily follow the same pattern, with anthotaxis in Michelia cited as being in 2/7, 3/7, 3/8, and 4/10 systems of arrangement.
Last Updated: 2020-01-01

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