Plant Cell Expansion: Regulation of Cell Wall Mechanical Properties

IN TRODUC TION .. . . . . . . . ... . . . ... . . ........ ..... ......... .... . . . . ...... 586 DIREC TIONALITY OF C ELL EXPANSION ...... 587 Dynamics of Wall Architecture . . . . . . . . ... 587 The Stress-Bearing Region of the Wall ........ . . . . . . . ...... 590 RATE OF C ELL EXPANSION .. ......... . .. . .. ... 591 Growth Equations .. . . . . . . . . . . . . . . . . 591 Th e In Vivo Cell Wall Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . 593 Physiological Control . . .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . ..... . . . . . . 597 CELL WALL MECHANICAL PROPER TIES . . . 607 Measurement and Interpretation .. . ........ . , 607 Mechanical Anisotropy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . ..... . . . . . . . . . . . . . . . . . . . . . ..... . .. . . . . . . . . . 614 Correlations with the Growth Ra te . . . . . . .. ......... 616 Effects of pH and Ions . . . . . . . . . . . . . . . . . . . 621 Proton Magn etic Resonance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . .. . . . . . . . . . 625 THE BIOCHEMIS TRY OF WALL EXTENSION ..... 626 Recent Views on Wall Molecular Structure ... . . . . 626 Cell Wall Enzymes and Polysaccharide Turnover . . 627 Noncovalent In teractions ........ . . . . . . . . . . . . . . . . . . . . . .. . ..... . ....... . .. . . . . ..... . . 632 Extensin and Polymer-Bound Phenolics . . . . . . .. . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . 635 Wall Synth esis . . .. . . . . . .. .. . . ... ... . . .... . . .. ......... 638 BRAVE N EW WALL . . 640