Plants at bodybuilding: Development of plant "muscles"

Abstract

Plant fibers are the important elements to shape the mechanical properties of plant body, especially in the organs that have already ceased elongation. The major distinguishing parameters of fibers are a highly prosenchimatous cell shape and an increased cell wall thickness as compared to other types of plant cells. The increase of fiber cell length is largely achieved by intrusive growth-elongation with the increased rate as compared to the adjacent cells and squeezing between them along the middle lamellae. The highly pronounced intrusive growth is the cause of fiber bundle formation. Thickening of cell wall in fibers of many plant species is supplied by deposition of the tertiary cell wall (G-layer) of peculiar design and properties. Tension of cellulose microfibrils is developed in this cell wall layer, providing the contractile properties that permit to move plant organs. We summarize the currently available data describing the inherent to fibers mechanisms by which they attain their exclusive length (intrusive growth) and extreme cell wall thickness (tertiary cell wall deposition) and consider the results obtained by finite element modeling to realize the cause of cellulose microfibril tension. The suggested hypothesis is based on the entrapment of tissue- and stage-specific version of rhamnogalacturonan I between laterally interacting cellulose microfibrils.