Evaluating the biomineral contents of plant cells for their diagnostic, systematic and environmental potential
Transmission electron micrograph (TEM) of a transverse section through raphides in a developing leaf of Amorphophallus bulbifer (Araceae). These needle-like crystals have a H-shaped outline which is characteristic of Araceae. Membranes orient the
In most plants, inorganic compounds are formed to varying degrees within specific cells and tissues; these biomineral compounds include calcium oxalate crystals and silicon dioxide aggregates (often termed phytoliths). In this project, the biomineral contents of plant cells are evaluated for their diagnostic, systematic and environmental potential, with particular emphasis on monocots.
Inorganic mineralisation in biological systems is an ancient process, dating from the time of the stromatolites, some 3500 million years ago. Many plant cells possess biomineral contents, such as opaline silica bodies (sometimes terned phytoliths) and different types of calcium oxalate crystal such as druses (cluster crystals), raphides (bundles of needle-like crystals) and solitary styloid crystals. These inorganic-based structures are formed under strict biological control by the selective uptake and subsequent inter- and intra-cellular deposition of elements from the local environment. Unlike the soft tissues in which they are deposited, these elements are packaged into an inert form that is resistant to decay; they remain well-preserved in soil profiles for thousands of years. Their presence in plant fossils and archaeological material can be employed for diagnostic purposes, including some economically important crop plants such as bananas, gingers, grasses, which possess silica bodies of characteristic shapes located in well-defined tissues. Thus, biominerals can represent significant markers in studies of agriculture and climate change. Few studies have been conducted, but there is some evidence that plant biomineralisation might be utilised in the sequestration of environmentally harmful elements such as global carbon and heavy metals in a form that may be chemically stable for thousands of years.
We study different types of crystals and silica bodies, with emphasis on commelinid monocots, to clarify the systematic and phylogenetic importance of these structures. We use multiple lines of evidence from morphology, ontogeny (LM anatomy, SEM, TEM) and immunolocalisation studies across a carefully selected range of taxa, to understand biomineral formation and development and to assess whether biominerals could ultimately be used as phytoremediators for the packaging of harmful pollutants.
We also study their development; some biominerals form within the vacuoles of actively growing cells, usually associated with membrane chambers, whereas others are deposited within the plant cell walls themselves. The physiological mechanisms of biomineral formation are not fully understood and accurate compositional knowledge of the biominerals themselves is lacking. New forms of biomineralisation are still being discovered. Pathways of biomineral uptake, deposition, and their development into characteristic morphological structures remain to be deciphered in order to fully understand whether these structures could potentially be harnessed as an environmental resource.
Key publications 2006-2011
- Prychid C.J., Jabaily, R.S. & Rudall, P.J. (2008). Cellular ultrastructure and crystal development in Amorphophallus (Araceae). Annals of Botany 101: 983–995.
Project partners and collaborators
Nigel Warwick (University of New England)
Davis, J.I. (Cornell University)