title: Cellular ultrastructure and crystal development in Amorphophallus (Araceae).
abstract: OBJECTIVE
  Species of Araceae accumulate calcium oxalate in the form of characteristically grooved needle-shaped raphide crystals and multi-crystal druses. This study focuses on the distribution and development of raphides and druses during leaf growth in ten species of Amorphophallus (Araceae) in order to determine the crystal macropatterns and the underlying ultrastructural features associated with formation of the unusual raphide groove.
  
  
  METHODS
  Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and both bright-field and polarized-light microscopy were used to study a range of developmental stages.
  
  
  RESULTS
  Raphide crystals are initiated very early in plant development. They are consistently present in most species and have a fairly uniform distribution within mature tissues. Individual raphides may be formed by calcium oxalate deposition within individual crystal chambers in the vacuole of an idioblast. Druse crystals form later in the true leaves, and are absent from some species. Distribution of druses within leaves is more variable. Druses initially develop at leaf tips and then increase basipetally as the leaf ages. Druse development may also be initiated in crystal chambers.
  
  
  CONCLUSIONS
  The unusual grooved raphides in Amorphophallus species probably result from an unusual crystal chamber morphology. There are multiple systems of transport and biomineralization of calcium into the vacuole of the idioblast. Differences between raphide and druse idioblasts indicate different levels of cellular regulation. The relatively early development of raphides provides a defensive function in soft, growing tissues, and restricts build-up of dangerously high levels of calcium in tissues that lack the ability to adequately regulate calcium. The later development of druses could be primarily for calcium sequestration.
authors.affiliation: Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3DS, UK. c.prychid@kew.org
authors.forename: Christina J
authors.initials: CJ
authors.lastname: Prychid
authors.forename: Rachel Schmidt
authors.initials: RS
authors.lastname: Jabaily
authors.forename: Paula J
authors.initials: PJ
authors.lastname: Rudall
mesh_terms: D029064:Araceae / Q000166:cytology / Q000378:metabolism / Q000648:ultrastructure*; D002129:Calcium Oxalate / Q000737:chemistry / Q000378:metabolism*; D003460:Crystallization; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D018515:Plant Leaves / Q000166:cytology / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D002129:Calcium Oxalate