Growth and Form

The link between shape and function allows understanding the evolutionary success of several organisms and their constituent parts. This is true in particular for diatoms, unicellular microalgae which contribute massively to primary production and carbon sequestration on a global scale, and which are characterized by an impressive diversity in dimension and shape within about 10³ genera and up to 10⁵ estimated species. The peculiar feature of diatoms is the frustule, a porous silica shell which encloses the protoplasm and which is characterized by the presence of regular patterns of micro- and nano-pores in an ultra-structured architecture. The diatom frustule seems to be involved in mechanical protection of the cell, sorting of nutrients from noxious agents, gas exchange, and efficient coupling with solar radiation. The aim of this short review is to give on one hand an overview of the main genetic mechanisms which finely control frustule morphogenesis and, on the other hand, to focus on its photonic properties, which could contribute to understand the extraordinary efficiency of diatoms in photosynthesis. The discussion on frustule morphogenesis and optical functions has been linked to Gielis transformations as an elegant and efficient tool to describe its geometry.