Author
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Ralph, John |
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Submitted to: Book Chapter
Publication Type: Book / Chapter Publication Acceptance Date: 8/26/2007 Publication Date: 11/1/2007 Citation: Ralph, J. 2007. Perturbing lignification. In: Entwistle, K., Harris, P.J., Walker, J., editors. The Compromised Wood Workshop. Canterbury, New Zealand:University of Canterbury. p. 85-112. Interpretive Summary: Perturbing lignification is possible in multiple and diverse ways. Without obvious negative effects on growth and development of the plant, transgenic angiosperms (hardwoods, grasses, legumes) can have lignin levels reduced to half the normal level, can have huge lignin compositional changes, and can even have their lignins incorporate significant levels of novel monomers. [Lignins are the polymers that are used by the plant in their cell walls to hold cellulose fibers together, facilitate water transport throughout the plant, and act as a defensive barrier]. Less has been accomplished in gymnosperms (softwoods), but lignin level reduction and alterations in the lignin composition appear possible. Such alterations in lignin composition and structure have marked impacts on chemical processing in processes such as alkaline pulping to produce fine paper or ethanolysis to provide cellulose for bioethanol production. However, the impacts on solid wood properties remain unknown. On the one hand, any structural changes in the polymer composite might be expected to influence wood properties. On the other hand, such properties are largely driven by non-lignin components and, importantly, by microfibril angle. The actual composition and structure of lignins may have little influence on certain solid wood properties. This chapter provides an overview into a diverse set of materials with extreme variations in lignin that should prove valuable to future research. Technical Abstract: Perturbing lignification is possible in multiple and diverse ways. Without obvious growth/development phenotypes, transgenic angiosperms can have lignin levels reduced to half the normal level, can have compositions ranging from very high-guaiacyl/low-syringyl to almost totally syringyl, and can even have their lignins incorporate significant levels of novel monomers. Less has been accomplished in gymnosperms, but lignin level reduction and alterations in the p-hydroxyphenyl:guaiacyl ratio appear possible. Such alterations in lignin composition and structure have marked impacts on chemical processing in processes such as alkaline pulping to produce fine paper or ethanolysis to provide cellulose for bioethanol production. However, the impacts on solid wood properties remain unknown. On the one hand, any structural changes in the polymer composite might be expected to influence wood properties. On the other hand, such properties are largely driven by non-lignin components and, importantly, by microfibril angle. The actual composition and structure of lignins may have little influence on certain solid wood properties. This chapter provides an overview into a diverse set of materials with extreme variations in lignin that should prove valuable to future research. |
