Comparative study of architecture and geometry of the date palm male and female inflorescences

The date palm, Phoenix dactylifera L. (Arecaceae), is a subtropical palm widely cultivated for numerous uses and ecosystematic services. The date palm is a dioecious species, which shows a marked dimorphism in inflorescence structure. To describe this dimorphism, architecture and geometry of male and female inflorescences were studied through kinetics of inflorescencial development and architectural and geometrical characterization of mature inflorescences. Two methodological approaches were used: a visual approach consisting of direct observations of inflorescence architecture of trees in situ and a technical approach through the valuation of different structural and geometric parameters of inflorescence. On every plant, inflorescence development is acrotone. Every palm leaf axils an inflorescencial bud. Inflorescence and female spikelets are longer than male ones. For female inflorescence, spikelets lengths are linked to their relative position on the rachis, the number of spikelets is on average 62, every spikelet carries 55 flowers on average. For male inflorescence, the length of spikelets seems independent of their relative position on the rachis. Number of spikes and flowers is higher with on average 236 spikes per rachis and 81 flowers per spike. In conclusion, architecture of male spikelets is more complex than female one. (Texte intégral)