Introduction : tissue organization and plasticity

This first lecture is intended as a general introduction to the theme of the Mechanics of Morphogenesis. Illustrating the diversity of form space, we outline the challenge of identifying general principles based on a physical description of biological processes. Starting with d'Arcy Thompson, an advocate of a purely mathematical, physicalist conception of form, the lecture first presents a model of tissue organization based on a thermodynamic description of the cell surface and the concept of surface tension. This is followed by a model of the dynamics of morphogenesis, identifying the active forces of hydrostatic pressure (in plants) and contractility (in animals), and the variable resistance offered by intercellular adhesion forces and/or cell wall elasticity.