Cystoliths are mineralized objects that are mainly composed of amorphous calcium carbonate (ACC), which is found in the leaves of several plants. Cystoliths function as internal-light scatterers that distribute the light flux more evenly inside the leaf.

By using various techniques including X-ray diffraction, Addadi et al, Weizmann Institute of Science, Israel, show that, within the same plant cystolith, four different mineral phases form one functional body. The silica stalk is essential for ACC formation and is composed of two different phases: the first ACC phase is more stable and creates a continuous biocomposite with the silica phase, whereas the second, less stable, ACC phase is the filler material that determines the final shape and volume of the cystolith.

The composite architecture of cystoliths may inspire new ACC-stabilization strategies that are dependent on tight regulation of the mineral microenvironment.

• Plant Cystoliths: A Complex Functional Biocomposite of Four Distinct Silica and Amorphous Calcium Carbonate Phases,
  A. Gal, A. Hirsch, S. Siegel, C. Li, B. Aichmayer, Y. Politi, P. Fratzl, S. Weiner, L. Addadi,
  Chem. Eur. J. 2012.
  DOI: 10.1002/chem.201201111