A dynamical phyllotaxis model to determine floral organ number

Area of Science:

• Developmental biology
• Plant science
• Mathematical modeling

Background:

• Organ number determination is crucial for precise body structures but developmental mechanisms remain unclear.
• Eudicot floral organs (sepals, petals) initiate sequentially and form whorls, typically with four or five organs.
• Previous models of plant phyllotaxis did not fully explain whorl formation.

Purpose of the Study:

• To propose and validate a development-based model for floral organ-number determination.
• To investigate the mechanisms driving the transition from sequential initiation to whorled arrangements.
• To explain the prevalence of tetramerous and pentamerous floral whorls.

Main Methods:

• Developed a computational model incorporating sequential primordia initiation and mutual repulsion.
• Analyzed the model numerically and analytically to observe emergent patterns.
• Incorporated a temporal decrease in primordia inhibition strength into the model.

Main Results:

• The model demonstrates that mutual repulsion among primordia spontaneously generates whorled arrangements.
• Pentamerous whorls, consistent with observed floral structures, become the dominant pattern.
• Tetramerous and pentamerous whorls are stable across a wider parameter space than hexamerous or heptamerous whorls.

Conclusions:

• Mutual repulsion during growth and decreasing inhibition during initiation are essential for developing common eudicot floral whorl numbers.
• The model provides a mechanistic explanation for the precise organ numbers observed in floral development.
• This work advances our understanding of plant morphogenesis and phyllotaxis.