Phyllotaxis

Phyllotaxis is the arrangement of leaves, seeds, or other plant organs around a growing axis. Its patterns often reflect regular spacing as new organs form.

Shoot apical meristem: The plant tissue at a shoot tip where new organs and stem tissues are produced. New leaves and floral organs arise around this growing region.
Divergence angle: The angle between successive organs around a plant axis. It is the basic measurement used to describe many phyllotactic patterns.
Opposite leaf arrangement: A leaf arrangement in which two leaves emerge at the same stem node, opposite each other. It contrasts with spiral arrangements around the axis.
Leaf area index: The ratio of leaf surface area to the ground area occupied by vegetation. Leaf arrangement affects how much foliage intercepts light within a canopy.
Auxin: A plant hormone that regulates growth and development, including organ formation at shoot tips. Local auxin accumulation helps mark sites where new organs initiate.
Fibonacci sequence: A sequence in which each term is the sum of the two preceding terms. Its consecutive numbers often appear as spiral counts in seed heads and cones.
Whorled leaf arrangement: A leaf arrangement in which three or more leaves emerge from the same stem node. It shows that repeated organ placement need not form a spiral.
Light interception: The capture of incoming light by a surface or canopy. Phyllotactic spacing can reduce overlap and distribute leaves through space.
Inhibitory field theory: A model in which developing organs inhibit the formation of new organs nearby. It explains why new primordia tend to arise at gaps between older ones.
Golden angle: An angle of about 137.5 degrees that divides a circle according to the golden ratio. Successive organs separated by this angle can form efficient, tightly packed patterns.

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