A physico-chemical approach to morphogenesis: the roles of inorganic ions and crystals.

We consider morphogenesis with special references to the development of mineral frameworks, organic filamentous structures and the location of enzymes, including ion-pumps, in membranes. Starting from a description of the morphology of inorganic crystals we analyse so-called equilibrium growth, i.e. growth at constant shape, both outside and inside biological systems. It is shown that an initial small spherical cell in which linear, ordered, inorganic or organic features are built will become distorted. The distortion is due to stresses which affect membrane curvature and consequently rearrange enzymes in membranes. The cell system can rapidly attain a steady-state of development, ('equilibrium') growth, of fixed morphology. After a considerable growth period the cell may cease to grow or the steady state may be broken and a transition can then occur to a quite new morphology. Examples are taken mostly from unicellular organisms but the ideas apply to multi-cellular systems.