Virtual phyllotaxis and real plant model cases

Phyllotactic pattern results from genetic control of lateral primordia size (physiological or physical) relative to the size of organogenic lateral surface of shoot apical meristem (SAM). In order to understand the diversity of patterns and ontogenetic transitions of phyllotaxis we have developed a geometric model allowing changes of the above proportion in a computer simulation ofSAM’s growth. The results of serial simulations confirmed thatmanyphyllotactic patterns (including most esoteric ones) and ontogenetic transitions known from real plantmodel cases can be easily obtained in silico. Properties of virtual patterns often deviated from those of ideal mathematical lattices but closely resembled those of the natural ones. This proved the assumptions of the model, such as initiation in the first available space or ontogenetic changes in primordia size, to be quite realistic. Confrontation of simulation results with some sequences of real phyllotactic patterns (case study Verbena) questions the autonomy of SAM in its organogenic activity and suggests the involvement of unknown signal positioning primordia in a non-random manner in the first available space. Additional keywords: Magnolia, ontogenetic transitions, pattern formation, SAM, Verbena. MAGNOLIA Sleepy flower on the leaf Creamy-white ivory Sweet to dizziness Fragrant thing Maliciously mysterious Universe Strange visitor among us, humans (Maria Pawlikowska-Jasnorzewska 1924)