Modelling architecture and growth patterns of Posidonia oceanica

The architecture and growth pattern of Posidonia oceanica was studied near Cannes, France in the Mediterranean from 80 samples collected at 6 m depth. Mathematical models were constructed iu order to quantify the distribution of internodes within growth units from different morphological types of ax es and branching orders. The results revealed that the frequency distributi on of the number of internodes per growth unit on plagiotropic axes changed according to branching order, passing from a Poisson distribution on order -1 axes, to a combination of a Poisson and a binomial distribution on order -2 axes, to a binomial distribution on order-3 axes. The production of inte rnodes per growth unit on orthotropic axes followed a binomial frequency di stribution. The distribution of internodes produced by transitional-plagiot ropic growth units was binomial despite the visual plagiotropic aspect of t hese units. The model shows that each year two statistically independent se ries of branches, with different probabilities according to branching order , occur in P. oceanica. The results are consistent with growth being regula ted by an internal biological clock, which emits three signals during the c ourse of the year. (C) 2000 Elsevier Science B.V. All rights reserved.