Density cell wall tissue

Figure 8.1 Possible strategies to control the material behavior in the axial direction at the cell and cell wall level, (a) Increase of stiffness and strength by thicker cell walls (tissue density), (b) Change of cellulose microfibril angle, (c) Alteration of matrix stiffness for a given high microfibril angle. Adapted from Eder et 2009, New Zealand Forest Research Institute Limited.

Different factors contribute to the mechanical properties of plant tissue cell turgor, which is one of the most important ones, cell bonding force through middle lamella, cell wall resistance to compression or tensile forces, density of cell packaging, which defines the free spaces with gas or liquid, and some factors, also common to other products, such as sample size and shape, temperature, and strain rate (Vincent, 1994). Depending on the sample properties (mainly turgor and resistance of middle lamella), two failure modes have been described (Pitt, 1992) cell debonding and cell rupture. 

Any procedure for wood specific gravity or density based on measuring weight and volume can be considered accurate only if the wood sample has been first extracted with suitable organic solvents to remove extraneous resins, oils, fats, gums, etc. (27). These materials bulk cell walls, block potential sites for water adsorption/ab-sorption, alter potential wood swelling/shrinkage, and thereby interfere with the accurate characterization of wood tissue. 

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