LAUSR

To test the hypothesis that particular tissues can control root growth, we analysed mechanical properties of cell walls belonging to different tissues of the apical part of maize root using atomic-force microscopy. The dynamics of properties during elongation growth were characterised in four consecutive zones of the root. The extensive immunochemical characterization and quantification were used to establish the polysaccharide motif(s) related to changes in cell wall mechanics. Cell transition from division to elongation was coupled to the decrease in the elasticity modulus in all root tissues. Low values of moduli were retained in the elongation zone and increased in late elongation zone. No relationship between the immunolabelling pattern and mechanical properties of the cell walls was revealed. When measured values of elasticity moduli and turgor pressure were used in the computational simulation, this resulted in an elastic response of modelled root and the distribution of stress and strain similar with those observed in vivo. In all analysed root zones, cell walls of the inner cortex displayed moduli of elasticity that were maximal or comparable to the maximal values among all tissues. Thus, we propose that the inner cortex serves as a growth-limiting tissue in maize roots.