ABSTRACT
The middle lamella in plants is defined as the intercellular substance acting as a cement that holds the cells together. This definition was formed based on optical, biochemical and biological studies that date back to the early 19th century. Numerous efforts were taken to construct a better understanding of this layer within the framework of the already established assumptions. However, we report some biological cases were the features of the middle lamella do not perfectly match our current definitions and create a sense of crisis with regard to our interpretation of this cell wall component. In this chapter, we studied the methods and models that were employed to characterise the middle lamella in an attempt to identify some features that need to be taken into consideration with regard to the current assumptions. The examination of the evolutionary aspect of the extracellular matrix (ECM) along with a rheological/chemical/biological investigation led to the hypothesis of Donnan–Gibbs equilibrium as a relevant mechanism that drives the creation of a middle lamella.
