Phyllotaxis Turns Over a New Leaf-A New Hypothesis

Area of Science:

• Plant biology
• Biophysics
• Developmental biology

Background:

• Phyllotaxis, the arrangement of plant organs, is a periodic phenomenon.
• Oscillators are generally responsible for periodic biological processes.
• The stem apical meristem (SAM) is crucial for plant development.

Purpose of the Study:

• To propose a hypothetical algorithm for phyllotaxis generation.
• To identify the key determinants regulating phyllotaxis.
• To explore the role of biochemical and mechanical forces in plant morphogenesis.

Main Methods:

• Modeling phyllotaxis using a Hechtian growth oscillator.
• Integrating biochemical gradients (auxin, protons, Ca2+) and mechanical forces.
• Analyzing the roles of cell wall-plasma membrane adhesion, ion channels, and protein pumps.

Main Results:

• The Hechtian oscillator integrates biochemical and mechanical signals to regulate morphogenetic gradients.
• Specific determinants, including SAM size, AGP-Ca2+ capacitor, proton pump, auxin efflux, and Ca2+ channels, control phyllotaxis.
• The model generates spiral and Fibonacci symmetries observed in phyllotaxis.

Conclusions:

• Arabinogalactan proteins (AGPs) and the AGP-Ca2+ capacitor play a decisive role in phyllotaxis periodicity.
• This model provides insights into the evolutionary origins of phyllotaxis.
• The proposed algorithm highlights the interplay of physical and chemical factors in plant development.