New insights into the structural organization of the plant polymer lignin.
The organizational features of lignin structure and the mechanism of its synthesis have significant implications for the response of the plant to stress. It was unknown whether the enzymic formation of lignin in the cell wall is an uncontrolled process or finely regulated in time and space. In vitro scanning tunneling microscopy (STM), atomic force microscopies (AFM), near-field scanning optical microscopy (NSOM). and the novel environmental scanning electron microscopy (ESEM) imaging studies of the lignin model compounds have directly shown its highly ordered structure and elucidated its modular and fractal organization. Direct evidence was presented for the existence of strong intermolecular forces responsible for holding lignin globules together in highly ordered structures. Fractal analysis was applied as a theoretical approach, to show regularity and modular organization of lignin. Surface chemistry studies of the lignin monolayer reveal intrinsic properties that may be a key to osmotic pressure and cell size control mechanism in the higher plant cells. The obtained data contribute to the explanation of the mechanisms of cell wall synthesis in vivo.