The riddle of phyllotaxis: Exquisite control of divergence angle

Abstract

Phyllotaxis studies published in German in the 1930s have reported intriguing regularity in the arrangement of incipient leaves on shoot apices of a wide variety of plant species. However, these studies have received little attention today, even though they provide a crucial evidence base for understanding this mathematical phenomena. Here I recapitulate the essential point by means of illustrative examples. It is emphasized that accurate control of apical divergence angle is at the heart of the numerical riddle of spiral phyllotaxis. Te accurate patterning at the shoot apex has an unexpected evolutionary beneft of being optimally adaptive in the subsequent events of phyllotactic change to occur on an elongating shoot.