The submicroscopic structure of plant cell walls

Abstract

1. (1) L. Hock investigated the Gough-Joule effect for rubber. In proving the effect, rubber was stretched. In this stretched rubber, parallel fibers were formed. These fibers were made visible by pouring liquid air over the stretched rubber and striking this rubber with a hammer. By treating undeformed rubber in a similar way, L. Hock found that this rubber was amorphous. 2. (2) The liquid air method used by L. Hock for rubber, was applied to the petioles of Nymphaea and woody branches of Salix babylonica. In the case of Nymphaea, the petiole on being struck with a hammer breaks up into irregularly formed particles. Therefore, the submicroscopic structure of the average secondary cell wall of petioles of Nymphaea consists mainly of amorphous cellulose. In the case of Salix bablyonica, on striking with a hammer, linear particles which lie nearly parallel to the axis of the branch were observed. Therefore, the submicroscopic structure in the average secondary cell walls of woody branches of Salix babylonica consists mainly of micellar cellulose. 3. (3) Certain cylindrical tissues of higher plants are more or less isotropic. These tissues are rubber-like in their elasticity and contain large amounts of amorphous cellulose in the average secondary cell walls. Other cylindrical plant tissues are anisotropic. These tissues are metallike in their elasticity and contain a great deal of crystalline cellulose in the average secondary cell walls. These conclusions were reached mainly from two experimental facts. The first was the ratio of the moduli of elasticity, the second, the observation based on freezing the material with liquid air. In addition, the conclusions were supported by the occurrence of different cellulose in dried and undried cotton fibers. 4. (4) Schematic drawings were made of the submicroscopic structure of the average secondary cell wall of the petioles of Nymphaea gladstonia and the woody branches of Salix babylonica. 5. (5) Rubber-like elasticity of plant tissues is at least partly exhibited by hydrated cellulose in the cell walls. 6. (6) Swollen cellulose fibers may have the same properties as high polymer fibers which are rubberdike. Dry cellulose fibers of ramie and cotton are metal-like. Hence, it is to be understood that not only cellulose fibers, but also cylindrical tissues of higher plants, are either rubberlike elastic or metaldike elastic. 7. (7) From specific gravity measurements, it is found that the percentage of cellulose in average secondary cell walls of cylindrical plant tissues increases with the ratio of the moduli of elasticity. 8. (8) From the ratio of the moduli of elasticity (9), the liquid air experiment, and measurements of specific gravity (10), it is found that the submicroscopic structure in all secondary ceil wails of higher plants is determinable by the percentage of cellulose and the ratio of amorphous and crystalline cellulose. The primary cell wall is highly plastic and contains a molecular network of cellulose (9).